Plants and plant products with potential antipsoriatic activity – a review

Abstract

Context: Psoriasis vulgaris is a hyper proliferative, autoimmune skin disorder affecting 1–3% of the world’s population. The prescribed synthetic drugs for the treatment of psoriasis are associated with severe side effects, thus, researchers around the globe are searching for new, effective, and safer drugs from natural resources.

Objective: The present review has been prepared with an objective to compile exhaustive literature on pharmacological reports on antipsoriatic plants, plant products, and formulations. An attempt has been made to incorporate chemical constituents (with structures) isolated from different plants responsible for antipsoriatic activity and their possible mechanism of actions in this review.

Materials and methods: The review has been compiled using references from major databases like Chemical Abstracts, Medicinal and Aromatic Plants Abstracts, PubMed, Scirus, Google scholar, Open J Gate, Scopus, Science Direct and Online Journals, and includes 127 references.

Results: A survey of literature revealed that extracts/fractions/isolates from 18 plants, 23 chemical constituents of plant origin and 40 plant-based formulations from various systems of medicine have been reported to possess antipsoriatic activity, and 37 antipsoriatic formulations containing plants have been patented.

Conclusion: Preliminary antipsoriatic activity studies have been carried out on crude extracts of traditionally used and medicinally promising plants. Such plants need to be explored properly with a view to isolate antipsoriatic constituents, and to evaluate their possible mode of actions so that these plant drugs could be exploited properly as potential antipsoriatic drugs.

Keywords::

• Antipsoriatic plants
• chemical constituents
• mode of actions
• pharmacological reports

Abbreviations:
BMI,	=	body mass index;
CBD,	=	cannabidiol;
CBG,	=	cannabigerol;
CBN,	=	cannabinol;
CIC,	=	circulatory immune complex;
DLQI,	=	dermatology life quality index;
ELISA,	=	enzyme linked immunosorbent assay;
IC50,	=	half maximal inhibitory concentration;
ICAM,	=	inter cellular adhesion molecule;
IFN-γ,	=	interferon gamma;
IL,	=	interleukin;
MTT,	=	3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide;
NB-UVB,	=	narrow band UV B;
NFκB,	=	nuclear factor kappa B;
PAF,	=	platelet activating factor;
PASI,	=	psoriasis area and severity index;
QLI,	=	quality of life index;
SRB,	=	sulforhodamine B;
TBDE,	=	trypan blue dye exclusion;
TGF β1,	=	transforming growth factor beta 1;
Th,	=	T helper cells;
TNF α,	=	tumour necrosis factor alpha;
TPA,	=	tissue plasminogen activator;
VEGF,	=	vascular endothelial growth factor;
Δ9-THC,	=	delta-9 tetrahydrocannabinol

Introduction

The present review article emphasizes pharmacological reports on antipsoriatic plants, plant products, and formulations. Various chemical constituents isolated from plants responsible for antipsoriatic activity and their modes of action have also been incorporated in the review. The review has been compiled using references from major databases including Chemical Abstracts, Medicinal and Aromatic Plants Abstracts, PubMed, Scirus, Google Scholar, Open J Gate, Scopus, Science Direct and Online Journals, and includes 127 references. A thorough survey of literature revealed that antipsoriatic activity has been carried out on crude extracts of plants. Thus, this review is needed for selecting such plants for further investigations to isolate antipsoriatic chemical constituents, and to establish their mode of actions. Moreover, the review will be of immense help to the researchers working in the field of natural products chemistry to study structure activity relationship of antipsoriatic constituents from plants, and to develop methods for synthesizing more efficacious and safer chemical analogues.

Psoriasis vulgaris

Psoriasis vulgaris is a common skin disorder characterized by focal formation of inflamed, raised plaques that constantly shed scales derived from excessive growth of skin epithelial cells (Krueger & Bowcock, 2005). It is evident that despite the difficulty in obtaining accurate statistics, psoriasis is a common worldwide disease with an incidence between 1 and 3% (Farber & McClintock, 1968). The disease has a complex pathophysiology involving genetic and cellular components. Accordingly, the therapeutic approach is very diverse, acting on different targets, varying from symptomatic treatment of reducing inflammation to modulating immune system. The exact cause of the disease is unknown but based on certain environmental factors like smoking, seasonal changes and infections, drugs are known to trigger the disease. Because of the deleterious effect on quality of life and serious side effects of the conventional treatment, the natural alternatives are being searched for. A number of plants have been used in traditional systems of medicines for psoriasis, which could act as safer alternatives to the conventional treatment.

Pathophysiology

Psoriasis was primarily considered a disorder of epidermal keratinocytes, however, it is now recognized as an immune-mediated disorder (Traub & Marshall, 2007). The disease is defined by a series of linked cellular changes in the skin, hyperplasia of epidermal keratinocytes, vascular hyperplasia and ectasia, and infiltration of T lymphocytes, neutrophils and other types of leucocytes in affected skin (Krueger & Bowcock, 2005).

Genetic basis

In psoriasis, self-reactive T cells do not destroy keratinocytes but stimulate them to proliferate (Krueger & Bowcock, 2005). This may be due to genetic predisposition leading to a high sensitivity of keratinocytes in patients to various activating stimuli. Other variants may result in inflammatory cells with a lower threshold for activation or a prolonged state of activation. Genome-wise linkage scans suggest at least nine different loci with susceptibility to psoriasis (PSORS 1–9). PSORS-1, a region of the major histocompatibility complex on chromosome 6p2, is the major genetic determinant of psoriasis. It accounts for up to 50% of genetic susceptibility to the disease, although the definitive gene has not yet been identified (Smith & Barker, 2006). One of the most compelling susceptibility factors for psoriasis is the presence of human leucocyte antigen (HLA)-Cw*0602, while other susceptibility loci for psoriasis reside on chromosomes 1q21, 3q21, 4q, 7p, 8, 11, 16q, 17q, and 20p.

Cellular basis

In psoriatic epidermis, keratinocytes proliferate and mature rapidly so that terminal differentiation, normally occurring in granular keratinocytes and then squamous corneocytes, is incomplete (Krueger & Bowcock, 2005). Hence, squamous keratinocytes aberrantly retain intact nuclei (parakeratosis) and release few extracellular lipids that normally cement adhesions of corneocytes. Accordingly, poorly adherent stratum corneum is formed and this results in the characteristic scale or flakes of psoriasis lesions. At the onset of the disease, special dendritic cells (DC) in the epidermis and dermis are activated (Mrowietz & Reich, 2009). These cells produce the messenger substances TNF-α and IL-23, which promote the development of certain subclasses of T cells (Th1, Th17). These T cells secrete mediators that contribute to the vascular and epidermal changes of psoriasis. The activation of intracellular signal transduction pathways plays an essential role in reinforcing the inflammatory immune reaction.

Etiology

About one-third of the people with psoriasis have a family history of the disease, but physical trauma, acute infection and some medications (e.g., lithium and β-blockers) are believed to trigger the condition (Naldi & Rzany, 2009). A few observational studies have linked the onset or relapse of psoriasis with stressful life events, and with personal habits including cigarette smoking and alcohol consumption. Others have found an association between psoriasis and body mass index (BMI) with a diet low in fruit and vegetables.

Epidemiology

Incidence

The average annual incidence rate is 54.4/100,000 for men and 60.2/100,000 for women (Cimmino, 2007). Psoriasis affects people of all ages, but there is a strong tendency for disease onset in early adulthood in patients who develop psoriasis due to genetic transmission (Krueger & Bowcock, 2005). The incidence of psoriasis increased with age for men, whereas the highest incidence for women it occurred in the 60–69 year age group.

Prevalence

Prevalence of psoriasis is usually set as 2%. Psoriasis is more frequent at northern latitudes and among Caucasians (Cimmino, 2007). The prevalence of psoriasis is low in certain ethnic groups such as the Japanese, and may be absent in aboriginal Australians and Indians from South America (Langley et al., 2005).

Types of psoriasis

Plaque psoriasis

The common form of psoriasis is plaque psoriasis in which patients may have sharply circumscribed, round-oval, or nummular (coin-sized) plaques (Langley et al., 2005; Traub & Marshall, 2007). The lesions may initially begin as erythematous macules (flat and 1 cm) or papules, extend peripherally, and coalesce to form plaques of one to several centimeters in diameter. Chronic plaque psoriasis form comprises approximately 90% of cases.

Guttate psoriasis

Guttate psoriasis describes the acute onset of a myriad of small, 2–10 mm diameter lesions of psoriasis (Langley et al., 2005; Traub & Marshall, 2007). These are usually distributed in a centripetal fashion although guttate lesions can also involve the head and limbs. It accounts for 2% of the total cases of psoriasis.

Flexural (inverse) psoriasis

Psoriasis affecting the flexures, particularly inframammary, perineal, and axillary, is distinct morphologically from traditional plaques elsewhere on the trunk and limbs (Langley et al., 2005; Traub & Marshall, 2007). Flexural lesions are devoid of scale and appear as red, shiny, well demarcated plaques occasionally confused with candidal, intertrigo, and dermatophyte infections.

Erythroderma

Total or subtotal involvement of the skin by active psoriasis is known as erythroderma and may take one of two forms (Langley et al., 2005; Traub & Marshall, 2007). Firstly, chronic plaque psoriasis may gradually progress as plaques become confluent and extensive. Secondly, erythroderma may be a manifestation of unstable psoriasis precipitated by infection, tar, drugs, or withdrawal of corticosteroids.

Generalised pustular psoriasis

It is rare, and represents active and unstable disease (Langley et al., 2005; Traub & Marshall, 2007). The patient is pyrexial, with red, painful, inflamed skin studded with monomorphic and sterile pustules, which may coalesce to form sheets.

Palmoplantar pustulosis

Palmoplantar pustulosis presents as sterile, yellow pustules on a background of erythema and scaling affecting the palms and/or soles (Langley et al., 2005; Traub & Marshall, 2007).

Psoriatic nail disease

The most common finding is small pits in the nail plate, resulting from defective nail formation in the proximal portion of the nail matrix (Langley et al., 2005; Traub & Marshall, 2007). Psoriatic nail disease occurs in approximately 50% of psoriasis patients.

Co-morbidities

Psoriasis is associated with several co-morbidities, including decreased quality of life, depression, increased cardiovascular risk, type 2 diabetes mellitus, metabolic syndrome, cancer, Crohn’s disease, and psoriatic arthritis (Traub & Marshall, 2007). It remains unclear whether cancers, in particular skin cancer and lymphoma, are related to psoriasis or to its treatment. Phototherapy and immunosuppressive therapy can increase the risk of non-melanoma skin cancer. Patients with severe disease seem to have higher incidence of mortality from cardiovascular disease (Smith & Barker, 2006). About one in four patients experience major psychological distress, and the extent to which they feel socially excluded is significant. In about 20% of the patients, an inflammatory disease of the joints called psoriatic arthritis (PsA) arises, usually many years after the initial cutaneous manifestation (Mrowietz & Reich, 2009).

Management

The selection of appropriate therapeutic approach for the treatment of psoriasis is based on forms of psoriasis including psoriasis vulgaris, guttate psoriasis and pustular/erythrodermic forms, and disease location such as scalp, nails, glabrous or intertriginous areas, and musculoskeletal involvement (Epstein, 1987).

Conventional treatment

Interventions comprise topical therapy, phototherapy, systemic (predominantly immunosuppressant) agents and biological treatments.

Topical therapy

Therapeutically active topical agents licensed for psoriasis include corticosteroids, vitamin D analogues, tar, dithranol, and tazarotene (Smith & Barker, 2006). Topical corticosteroids are prescribed for psoriasis in enormous quantities. Stronger steroids are obviously more effective but more likely to produce atrophy and systemic absorption (Champion, 1981). Tar and keratolytic agents are applied topically to provide adjunctive aid in helping to control stable hyperkeratotic forms of psoriasis (Epstein, 1987). Keratolytic agents such as salicylic acid (2–10%) have been used to remove excess scale, thus enhance penetration and bioavailability of concurrently used topical agents. Dithranol is perhaps the most effective topical remedy available, but its tendency to cause staining of clothes and skin and to cause inflammation somewhat restricts its use (Champion, 1981). Vitamin D analogues are as potent as corticosteroids and more effective than dithranol (Smith & Barker, 2006). Calcipotriol is marginally more effective than tacalcitol or calcitriol. It has been found that vitamin D in combination with a potent steroid is more effective than calcipotriol alone. The calcineurin inhibitors tacrolimus (1%) and pimecrolimus are prescribed occasionally for severe flexural or facial psoriasis.

Phototherapy

Systemic PUVA (Psoralen-UVA), balneo-PUVA and UVB therapy are all effective for the treatment of severe psoriasis (Claes et al., 2006). The combination of UV therapy with vitamin D3 analogues or with topical steroids is more effective than the treatment with UV radiation alone. Salt water baths increase the effectiveness of UVB therapy.

Systemic therapy

For over 20 years, methotrexate (MTX) has been an extremely effective and useful drug in the management of severe psoriasis. Another useful drug, hydroxyurea, has been used for treatment of psoriasis but it is less effective than methotrexate (Champion, 1981). Etretinate, a systemic retinoid has been recommended for the treatment of exfoliative and generalized pustular psoriasis (Dantow, 1992). Cyclosporine, a potent and toxic drug, is sometimes considered for some cases, where psoriasis is not controlled by conventional therapy such as acitretin, PUVA or MTX, but it shows contraindication in patients with abnormal renal function, poorly controlled hypertension, hepatic dysfunction or immunosuppression (Traub & Marshall, 2007).

Biological treatments

These are agents that block molecular steps important in the pathogenesis of psoriasis (Smith & Barker, 2006). Biological therapies for the treatment of psoriasis are classified into three categories, the T-cell modulating agents (alefacept and efalizumab), the inhibitors of tumor necrosis factor-α (TNFα blockers, e.g., adalimumab, certolizumab, etanercept, golimumab and infliximab), and the inhibitors of IL-12 and IL-23 (ustekinumab and briakinumab).

Antipsoriatic plants

A thorough survey of literature revealed that a number of plants such as Aloe vera, Centella asiatica, Panax ginseng, Rubia cordifolia, Saccharum officinarum, etc. have been reported to exhibit antipsoriatic activity. Table 1 shows antipsoriatic activity reports on such plants, and information covered include biological source (botanical name, family and common names) of plant, extract/fraction/isolate of plant part used, bioactive dose, route of administration, animals/human beings, experimental model/clinical study and mode of actions (if reported). Antipsoriatic activity reports on various chemical constituents of plant origin are depicted in Table 2. The information covered in Table 2 includes name and structure of pure constituent, bioactive dose, route of administration, animals/human beings, experimental model/clinical study and mode of actions (if reported). Figure 1 shows structures of various constituents reported to possess antipsoriatic activity. Appropriate numbers have been assigned to all structures as well as to their corresponding constituents. A number of plant-based formulations from various systems of medicine such as Chunghyleldan (Chinese medicine), Imupsora (Ayurvedic formulation) and Majoon Ushba with Raghane (Unani formulation) have shown potential antipsoriatic activity. The list of such formulations with their composition, and antipsoriatic activity reports covering information on bioactive dose, route of administration, animals/human beings, experimental model/clinical parameters assessed and mode of actions (if reported) are depicted in Table 3. Thirty-seven antipsoriatic plant products and formulations are patented in Table 4.

Table 1.  List of various plants reported to possess antipsoriatic activity.

S. No.	Plant drug	Extract/fraction/ isolate	Dose	Animals/human beings	Experimental model/clinical study	Mode of action	Reference
1.	Aloe vera (L.) Burm. (Liliaceae) Ghritakumari	Extract of leaves (0.5%) in hydrophilic cream	Topical; three times daily for five consecutive days per week (4 weeks)	Human patients	Double blind, placebo controlled study (PASI)	–	Syed et al., 1996
2.	Angelica dahurica Fisch. ex Hoffm. (Apiaceae) Bai Zhi/root of the holy ghost	Aqueous extract of roots	Topical, followed by UV-A exposure	Skin specimens of psoriatic patients	Examining with electron microscope	Accelerates degeneration and breakdown of psoriatic cells, and normalizes proliferation of basal cells	Chen & Zhang, 1987
3.	Betula alleghaniensis Britt. (Betulaceae) Yellow birch	Polyphenolic extract of bark	In vitro; 24 and 48 h exposure	Normal human keratinocytes (NHK) and psoriatic keratinocytes (PK)	MTT assay and TBDE method (antiproliferant and antioxidant)	–	García-Pérez et al., 2010
4.	Caesalpinia bonduc (L.) Roxb. (Caesalpiniaceae) Fevernut/Gray nicker bean	Butanol and water fractions of hydro-alcoholic extract of leaves	(a) 500 mg/kg body weight	(a) Swiss albino mice	(a) Mouse tail test	–	Muruganantham et al., 2011
			(b) IC50=77.5±12.7 µg/ml (CBHA)	(b) HaCaT cell lines	(b) In vitro lipoxygenase inhibition and antiproliferant assay
5.	Celastrus orbiculatus Thunb. (Celastraceae) Nan She Teng/oriental bittersweet	NST Crude extract	15, 30 or 45 µg/ml for 48 h. IC50 = 29.4 µg/ml	Human HaCaT keratinocyte cell lines	SRB and MTT assays	Induction of apoptosis (antiproliferative effect)	Zhou et al., 2011
6.	Centella asiatica (Linn.) Urban. (Apiaceae) Gotu kola/Indian Pennywort	(a) Aqueous extract of aerial parts	(a) IC50 = 209.9 ± 9.8 mg/ml	SVK-14 keratinocytes	In vitro bioassay (antiproliferant activity)	Inhibition of keratinocyte replication	Sampson et al., 2001
		(b) Madecassoside (1), Asiaticoside (2)	(b) IC50 = 8.6 ± 0.6 µM
7.	Coptis chinensis Franch. (Ranunculaceae) Goldthread	Ethanolic extract (80%) of rhizomes	IC50 = 23.4 µg/ml	HaCaT cell lines	In vitro tests (micro plate SRB and MTT assays) [antiproliferative activity]	–	Tse et al., 2006
8.	Eruca sativa Mill. (Brassicaceae) Rocket seeds	4-Methylthiobutyl-isothiocyanate (3) from aqueous extract of seeds	0.5, 1 µg/ml for 3 days. IC50= 0.8 µg/ml or 50 µM	Keratinocytes and THP-1 monocytes	In vitro tests (antiproliferative)	–	Yehuda et al., 2009
9.	Mahonia aquifolium Rubisan (Berberidaceae) Oregon grape	Ointment prepared from aqueous extract of fruits	Topical (12 weeks)	433 Human patients	Prospective, open multi centre trial (PASI)	–	Gieler et al., 1995
		Cream prepared from aqueous extract of fruits (10%)	Topical (12 weeks)	39 Human patients	Open label study (PASI, DLQI, PDI)	–	Gulliver & Donsky, 2005
		Cream prepared from aqueous extract of fruits (10%)	Topical (6 months)	32 Human patients	Clinical trial (comparison with standard)	–	Gulliver & Donsky, 2005
		Cream prepared from aqueous extract of fruits (10%)	Topical (1 month)	33 Human patients	Observational study	–	Gulliver & Donsky, 2005
10.	Panax ginseng C.A. Meyer (Araliaceae) Ginseng	Cream prepared from a Compound K isolated from aqueous extract of roots (0.02% and 0.05%)	Topical application for 16 days	Albino mice	Oxazolone-induced mouse ear dermatitis	Regulation of COX-2 produced by macrophage cells and interferon-γ and IL-4 induced by Th cells	Shin et al., 2005
11.	Picea mariana (Mill.) Britton, Sterns & Poggenb. (Pinaceae) Black spruce	Polyphenolic extract of bark	In vitro; 24 and 48 h exposure	Normal human keratinocytes (NHK) and psoriatic keratinocytes (PK)	MTT assay and TBDE method (antiproliferant and antioxidant)	–	García-Pérez et al., 2010
12.	Pinus maritima L. (Pinaceae) French maritime pine bark	Pycnogenol (4) isolated from aqueous extract of bark	50 µg/mL, 12 h pre -treatment time	Human keratinocyte cell line, HaCaT	In vitro study (antiinflammatory)	Inhibition of inducible ICAM-1 expression in HaCaT cells, thus, downregulating T-cell adhesion	Bito et al., 2000
13.	Polypodium decumanum Willd. (Polypodiaceae) Calaguala	Sulphoquinovosyldiacyl-glycerol 1,2-di-O-palmitoyl-3-O-(6-sulpho-α-d-quinovopyranosyl)-glycerol	IC50 = 2 µM	Human neutrophils	PAF induced exocytosis model	PAF receptor antagonism in intact neutrophils	Vasänge et al., 1997
14.	Pongamia pinnata Linn. (Fabaceae) Pongam oil tree/Indian Beech	Biflavonyloxymethane	1 µg/mL	In vitro	–	Antioxidant, radical quenching activity	Ghosh et al., 2011
15.	Rubia cordifolia Linn. (Rubiaceae) Common madder/Radix Rubiae	Ethanolic extract of roots	IC50 = 1.4 µg/mL	HaCaT cell lines	In vitro tests (micro plate SRB and MTT assays) (antiproliferative activity)	PAF receptor antagonism in intact neutrophils	Tse et al., 2006
16.	Saccharum officinarum Linn. (Graminae) Sugarcane	Wax oil (mixture of fatty acids)	Topical	Albino mice	Tail test for psoriasis	–	Ledón et al., 2007
17.	Tabebuia avellanedae Lor. ex. Gris (Bignoniaceae) Red lapacho tree	Herbal tea from the inner bark	In vitro	Human keratinocyte cells	In vitro tests (antiproliferative activity and MTT assay)	–	Ohta et al., 2010
18.	Thespesia populnea (L.) Sol. ex Corria (Malvaceae) Portia tree, Indian Tulip tree	Bark extracts	Topical	Albino mice	Perry’s scientific mouse tail model (increase in orthokeratotic region)	–	Shrivastav et al., 2009
		(a) Butanolic extract cream
		(b) Petroleum ether extract cream
		(c) TpF-1, TpF-2, TpS-2

MTT, 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide; TBDE, trypan blue dye exclusion; SRB, sulforhodamine B; PAF, platelet activating factor; DLQI, dermatology life quality index; Th, T helper cells.

Table 2.  List of various constituents isolated from plants reported to possess antipsoriatic activity.

S. No	Active constituent	Plant sources	Dose	Animals/ Human beings	Experimental model/clinical study	Mode of action	Reference
1.	Artesunate (5)	A derivative of artemisinin produced from plant Artemisia annua L. (Sweet Wormwood; Asteraceae)	0.01–0.5 mg/mL	Keratinocyte cell line HaCaT	In vitro study (MTT assay)	Antiproliferant action by regulating the expression of CXCR2 and enhancing the secretion of TGF β1 in vitro	Jin et al., 2007
2.	Camptothecin (6)	Camptotheca acuminata Decaîsne (Heaven wood tree; Nyssaceae), Nothapodytes nimmoniana (J. Graham) Mabberly (Ghanera; Icacinaceae)	0.5 mg/mL	Albino mice	Mouse vaginal epithelium at estrus and mouse tail epidermis model	Inhibiting proliferation and inducing differentiation	Huang & Lin, 1996
3.	Cannabinoids [Δ-^9THC (7), CBN (8), CBD (9), CBG (10)]	Cannabis sativa L. (Hemp; Cannabaceae), Cannabis indica Lam. (Asian Hemp; Cannabaceae), Echinacea purpurea (L.) Moench (Eastern purple coneflower; Asteraceae), Echinacea angustifolia de Candolle (Narrow-leaved purple coneflower; Asteraceae), Echinacea pallida Nutt. (Pale Purple Cone-flower; Asteraceae), Acmella oleracea (L.) R.K. Jansen (Toothache plant; Asteraceae), Helichrysum umbraculigerum Less. (Kerrikruie; Compositae), and Radula marginata Taylor (Radulaceae)	72 h incubation of cannabinoids dissolved DMSO diluted 100-fold into Epilife growth medium IC50 = 2.3 µM	Human keratinocyte cell line	In vitro study (SRB keratinocyte proliferation assay)	–	Wilkinson & Williamson, 2007
4.	Capsaicin (11)	Capsicum annuum L. (Chili pepper; Solanaceae)	Topical, 6 weeks	Human patients (44)	Double blind study	–	Bernstein et al.,1986
			Topical, 0.025% cream, 4 times a day for 6 weeks	Human patients	Double blind study	–	Ellis et al., 1993
5.	Colchicine (12)	Colchicum autumnale L. (Autumn crocus; Colchicaceae)	0.02 mg/kg per day, p.o. for 2–4 months	Human patients (22)	Human study (therapeutic trial)	Antichemotactic	Wahba & Cohen, 1980
			Oral, 2 weeks	Human patients (4)	Open study	-	Zachariae et al.,1982
6.	Curcumin (13)	Curcuma longa L. (Turmeric; Zingiberaceae)	Gel, 2–6 weeks	Human patients	Human study (90% plaque resolution in 50% patients, 50–85% in remainder)	Selective phosphorylase kinase inhibitor, thereby reducing inflammation through inhibition of NFκB	Traub & Marshall, 2007
			4.5 g/d oral curcuminoid C3 complex	Human patients	Phase two, open label, Simon’s 2 stage trial (PASI, PGAS)	–	Kurd et al., 2008
7.	Embelin (14)	Embelia ribes Burm.f. (False Black Pepper; Myrsinaceae)	Topically, once a day for 10 days each morning immediately after TPA application	Female Balb/c mice	TPA induced mouse ear edema	Inhibition of IL-1β and TNF-α and subsequent blockade of leukocyte accumulation	Kalyan Kumar et al., 2011
8.	Fumaric acid (15) esters	Fumaria officinalis L. (Common Fumitory; Fumariaceae), Boletus fomentarius L. var. pseudo-igniarius (Bolete mushrooms; Polyporaceae)	30 mg or 120 mg (6 tablets)	Human patients	Improvement in 55% of patients	Inhibition of T cell activity via induction of apoptosis	Harries et al., 2005
9.	Gossypol (-) (16)	Gossypium species (Cotton; Malvaceae)	GI50 = 4.8 μM	HPV-16 keratinocyte cell line	In vitro study (MTT assay and TBA test)	Antiproliferative and antioxidant	Dodou et al., 2005
10.	Hypericin (17)	Hypericum perforatum L. (St John’s Wort; Hypericaceae)	Topical, for 4 h followed by irradiation with 500W halogen lamp	Hairless mice	Mouse epithelial test	Penetrated skin in photo-active concentration and treated erythema, desquamation and erosions	Kamuhabwa et al., 1999
11.	iso-Camptothecin	Camptotheca acuminata Decaîsne (Heaven wood tree; Nyssaceae)	51 μg/mL for 24 h, 48 h	Human keratinocyte cell line HaCaT	In vitro	Inhibits keratinocyte proliferation, induces apoptosis and down regulates telomerase	Lin et al., 2008a
12.	Koumine (18)	Gelsemium elegans (Gardner & Champ.) Benth. (Loganiaceae)	6, 30 or 150 mg/kg, p.o.	Albino mice	Mouse vaginal epithelium and mouse tail epidermis model	Inhibition of epidermal cell proliferation, promoting formation of granular cells, decreasing serum IL-2 levels	Zhang et al., 2005
13.	Podophyllotoxin (19)	Podophyllum species - Podophyllum peltatum L. (Mayapple; Berberidaceae), Podophyllum hexandrum Royle (Himalayan Mayapple; Berberidaceae)	0.1%, 0.25% or 0.5% in an ointment base	Human patients (152)	16-week double-blind study of parallel groups	–	Lassus & Rosen, 1986
14.	Psoralen [8- methoxy psoralen] (20)	Psoralea corylifolia L. (Babchi; Fabaceae)	Oral (followed by exposure to long UV radiation)	Human patients (21, adult, Caucasian)	Clinical study (complete clearance)	Inhibition of epidermal DNA synthesis and thereby cell division	Briffa & Warin, 1979
			Oral (followed by exposure to long UV radiation), 25 exposures (2–3 times a week), 12 weeks	Human patients (1308)	American Cooperative Clinical Trial (clearance in 88% of patients)
15.	Isoquinoline (21)	Argemone species (Prickly poppy; Papaveraceae), Chelidonium species (Celandine poppy; Papaveraceae), Corydalis species (Fitweed; Fumariaceae), Dicentra species (Dutch man’s breeches; Fumariaceae), Papaver species (Poppy; Papaveraceae), Sanguinaria species (Bloodroot; Papaveraceae)	0.2% in white vaseline/ lanette wax cream 50%/50%, 0 and 7 days	Human patients (35), out of these 18 were taken as control group	Human tape stripping model and double blind scoring of two randomly selected lesions	–	Arnold et al., 1993
	Sphingosine (2-amino-4-octadecene-1,3-diol) (22)	An 18-carbon amino alcohol with an unsaturated hydrocarbon chain, which forms a primary part of sphingolipids, a class of cell membrane lipids that include sphingomyelin, an important phospholipid	0.1 M in ethanol, 13 days
	Tannic acid (23)	Caesalpinia spinosa (Molina) Kuntze (Tara pods; Fabaceae), Rhus semialata Murr. (Arkhar; Anacardiaceae), Quercus infectoria Olivier (Gall Oak; Fagaceae), Rhus coriaria L. (Elm-Leaved Sumach; Anacardiaceae)	0/10% tannic acid in lanette wax cream, 0 and 7 days
	Isoquinoline (21) and tannic acid (23)		0.0/0.2% isoquinoline and 0/10% tannic acid, 21 days

TGF β1, transforming growth factor beta 1; MTT, 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide; TGF β1, transforming growth factor beta 1; SRB, sulforhodamine B.

Table 3.  List of various plant-based antipsoriatic formulations.

S. No.	Formulation	Dose	Animal	Experimental model/Clinical study	Mode of action	Reference
1.	Amrutballatak Avaleha (Bhallatak and guduchi) + Karanjadi lepa (kandughna and kusthagna) (Ayurvedic medicine)	Orally (90 days) + topically (90 days)	Human patients (60 cases)	Positive response in comparison to placebo	–	Dave & Shukla, 2006
2.	Ginkgo and megranate (Chinese medicine)	In vitro	Human patients (46-VEGF and 33-PIGF)	ELISA method (serum VEGF levels), Immuno-histochemical technique (PIGF)	Downregulates the expression of VEGF and PlGF	Qiang et al., 2008
3.	Chunghyuldan (Scutellariae Radix, Coptidis Rhizoma, Phellodendri Cortex, Gardeniae Fructus, Rhei Rhizoma) (Chinese formulation)	0.1%	Albino mice	Oxazolone induced mouse ear dermatitis	Regulation of COX-II produced by macrophage cells, and IFN-γ and IL-4 produced by Th cells	Wee et al., 2005
4.	Composite Shendi decoction (CSDD) and Diyin tablet (DYT) (Chinese formulation)	One tablet	Human patients (35)	Clinical study	Serum IL-8 and plasma endothelin level reduced	Gao & Xu, 2001
5.	Compound Zeqi granules (Euphorbia) (Chinese formulation)	Oral (3 months duration)	Human patients (52)	Human study (DLQI, PASI)	–	Sun et al., 2010
6.	Glyteer (delipidated soybean)	Topical (6 h, 3 days after TPA treatment)	Albino mice	Mouse psoriasis model (edema and epidermal hyperplasia in mouse ear by TPA)	–	Ito et al.,1992
7.	Herose capsules (Rhizoma Zingiberis, Radix Salviae miltiorrhizae, Radix Astragali, Ramulus Cinnamomi, Radix Paeoniae alba, Radix Codonopsis Pilosula, Semen Coicis) (Chinese formulation)	Four capsules (450 mg each), three times a day for 10 months	Human patients (15)	Open study (conducted in one centre)	–	Yuqi, 2005
8.	Huayin powder (Chinese formulation)	Inhalation	Human patients (34)	Clinical study (CIC, MMS)	–	Yang et al., 1996
9.	Imupsora tablet (Ayurvedic formulation)	3 months (2 tablets twice daily + ointment application thrice daily)	Human patients (50)	Open labelled study (PASI)	–	Saple et al., 2008
10.	Indigo naturalis	Ointment (topical for 12 weeks) Extracts (10–500 µg/ml) indirubin active)	Human patients (42)	Randomized, observer blind vehicle controlled, intrapatient comparison study	–	Lin et al., 2008b
		Extracts (10–500 µg/ml) (indirubin active)	(a) Cultured keratinocytes	(a) In vitro studies (antiproliferative)	Modulating proliferation and differentiation of keratinocytes	Lin et al., 2009
			(b) Human skin samples (6 patients)	(b) Immuno-histochemical studies
11.	Jiedu Quyu formula (Chinese formulation)	One week	Human patients (70)	Clinical study (PASI, Plasma endothelin level)	–	Sun & Xu, 2009
12.	Liangxue huoxue xiaoyin tang decoction [(Bai Mao Gen (Imperatae Rhizoma) – 30 g, Ban Lan Gen (Isatidis Radix) – 30 g, Sheng Di (Rehmanniae Radix) – 15 g, Zi Cao (Arnebiae Seu Lithospermo Radix) – 15 g, Qian Cao (Rubiae Radix) – 15 g, Chi Shao (Paeoniae Rubra Radix) – 15 g, Dan Shen (Salvia Miltirrhizae Radix) – 15 g, Jixue Teng (Spatholobi Caulis) – 30 g] (Chinese formulation)	One week	Human patients	Radio immunoassay and ELISA	Reducing serum levels of TNF-α, IFN- γ and IL-6	Qiu et al., 2005
13.	Liangxue Jiedu decoction (Chinese formulation)	Two weeks	Albino mice	Mouse psoriasis model	-	Gu et al., 2009
		Eight weeks	Human patients (41)	Randomized, single blind and controlled study (ELISA, PASI)	-	Liu et al., 2010
14.	Liangxue Piyan granule (Chinese formulation)	Oral	Human patients (96)	Clinical study	-	Mao et al., 1997
15.	Lixue xiaoyin decoction (Chinese formulation)	Oral, 8 weeks	Human patients (118)	Radio immunoassay (ET content)	Improves microcirculation and inhibits division of epidermal cells	Zhou & Tao, 2005
16.	Majoon Ushba + Roghane Hindi (Unani formulations)	Orally on empty stomach, 5 g twice daily + 5-10 ml topically twice daily (8 weeks)	Human patients (30)	Randomized, single-blind, placebo-controlled study	-	Lone et al., 2011
17.	Marham-e-Gulabi (Plumbum, beeswax, boric acid, phenol, coconut oil) + Psoralea corylifolia Linn. (Unani formulation)	6 g Safoof-e-Babchi twice a day in form of zulal (decant water) on empty stomach and apply Marham-e-Gulabi on lesions once a day (45 days)	Human patients (40)	Clinical improvement in 77.5% patients	-	Khan et al., 2009
18.	New Pulian ointment (Radix Scutellariae, Cortex Phellodendri, Indigo Naturalis, and Radix Arnebiae seu Lithospermi) (Chinese formulation)	Topical (single blinded method twice a day) for 4 weeks	Human patients (108)	Randomized controlled trial (PASI)	-	Zhou et al., 2009
19.	Pifubin xuedu pill combined with diyin tablet (Chinese formulation)	One tablet daily for 1 month	Human patients (60)	Clinical study	-	Yang et al., 2005
20.	Psirelax (Grape seed oil, African palm oil, Jojoba oil, Sunflower seed oil, Guar gum, Wheat germ oil, Flaxseeds extract, Cera alba)	Topical (twice a day for 4 weeks)	Human patients (22)	Open label study (PASI)	-	Shiri and Cohen, 2010
21.	Qingdai compound capsule (Chinese formulation)	Oral	Human patients (30)	Immuno histochemical studies	Decrease in expression of c-myc in keratinocytes	Feng et al., 1996
22.	Qinzhu Liangxue decoction (Chinese formulation)	4 weeks, 30 ml (2.1g/ml), oral, morning and evening, before meals	Human patients (58)	Randomized, control trial (PASI, DLQI)	–	Li et al., 2008
23.	Qoolskin [Water (Aqua), Glycerin, Riboflavin, Citrus medica Limonium (Lemon) Juice, Vinegar, Taraxacum officinalis extract, Cereus grandiflorus (Cactus) flower extract, Opuntia coccinellifera fruit extract, Ascorbic acid, Calcium ascorbate, Tartaric acid]	Topical, 2–3 times per day, for 16 weeks	Human patients (100)	Open-label, parallel group study (clinical assessment-PASI, BPSS)	–	Cohen et al., 2007
24.	Quyin granule (Chinese formulation)	3 doses—low, middle, high	Albino mice	Mouse tail test and mouse vaginal epithelium test	Inhibition of faster epidermal cell proliferation and improvement of parakeratotic epidermal cells	Bai et al., 2007
25.	Radix Sophorae Flavescentis (Sophora flavescens Ait.)	i.p. injection of aqueous extract	Albino mice	Mouse vaginal epitheliun in estrus cycle and mouse tail scaled epidermis	Inhibition of hyperplasia of epidermis cells and the promotion to the formation of granular layer	Song et al., 2002
26.	Relieva (Mahonia aquifolium)	Topical cream, twice a day for 12 weeks	Human patients (200)	Randomized, double blind, placebo controlled study (PASI, QLI)	–	Bernstein et al., 2006
27.	Urea, sunflower oil, evening primrose oil, wheat germ oil, Sodium pyruvate	Topical, 1 month	Human patients (hyperkeratotic skin condition)	Randomized double-blind clinical trial	–	Ferrando, 1986
28.	Tuhuai extract (Flos sophorae, Smilax glabra Roxb., licorice)	Topical, 1% extract (twice daily for 4 days)	Albino mice	Murine disease models–Epidermal hyperproliferative model, and irritant and allergic contact dermatitis model	Antiproliferative and antiinflammatory	Man et al., 2008
29.	Vitamin B12 cream containing Avocado oil	Topical, 12 weeks	Human patients (13)	PASI score	–	Stücker et al., 2001
30.	Xiangfangxiaoyinpin (Chinese preparation)	Infusion, once a day for 14 days	Albino mice	Mouse tail flake test (granular cell proliferation)	–	Liu et al., 2006
31.	Xian-fang-xiao-yin tablet (Chinese preparation)	Oral	Human patients (50)	Radioimmunoassay	Inhibits proliferation of cells and formation of new vessels	Liu et al., 2005a
32.	Xiaoyin recipe (Chinese preparation)	4 weeks or 8 weeks	Human patients (32)	PASI, TNF-α level	Reduction of TNF-α	Zhang et al., 2008
33.	Yinxieling (YXL) [Rhizoma Smilacis Glabrae, Rhizoma Smilacis Chinensis,	Fumigation	Human patients (30)	Western blot method	Modulating equilibrium of transcription factors T-bet and GATA-3	Wei et al., 2008
	water and ethanol] (Chinese formulation)				protein expressions in peripheral blood monocytes
		–	Albino Mice	Histamine shock of guinea pigs, delayed hypersensitivity of mice, mouse otitis by croton oil	Immune suppression and antiinflammatory	Liu et al., 1999
34.	Yinkang granules (Chinese formulation)	Oral	Human patients (98 – treatment, 50 – control)	Clinical observation	-	Chen et al., 2001
35.	Yinxie capsules (Cornu Bubali, Radix Rehmanniae, Radix Arnebiae seu Lithospermi, Radix Paeo- niae Rubra, Cortex Moutan, Herba Portulacae Grandiflorae, Herba Hedyotis Diffusae, Semen Coicis, Radix Salviae Miltiorrhizae, Folium Isatidis, Herba Lycopi, Rhizoma Cureumae, Cortex Dictamni and Radix Glycyrrhizae) (Chinese formulation)	Oral, 6 weeks	Human patients (75)	PASI	-	Xi et al., 2008
36.	Yinxiebing external bath formula and narrow spectrum mid-wave UV radiation (Chinese formula)	Bath formula (external application)	Human patients (80)	Clinical study (Total effective rate- 95%)	-	Liu et al., 2005b
37.	Yinxieling tablets (YT) (Chinese formulation)	4 weeks	Human patients (48)	Clinical observation (PASI)	Decrease of serum IFN- γ level	Wang et al., 2009
38.	Yuyin recipe combined with narrow band UV-B (NB-UVB) (Chinese treatment)	NB-UVB and YYR bathing, 8 weeks	Human patients (119)	Human study (PASI)	–	Cui et al., 2008
39.	Zhuhuang granule no. 2 (Chinese formulation)	Oral	Human patients (77)	Radioimmunoassay	–	Yang et al., 2001
40.	Zicahuoxue decoction (Chinese formulation)	Oral	Human patients (92)	Clinical study (skin lesion area, erythema, pruritis, PASI)	–	Wang et al., 2003

DLQI, dermatology life quality index; ELISA, enzyme linked immunosorbent assay; PASI, psoriasis area and severity index; QLI, quality of life index; CIC, circulatory immune complex.

Table 4.  List of antipsoriatic patents having plant products.

S. No.	Composition	Formulation	Reference
1.	Carthami tinctorii Flores, Guaiacum officinale, Pardanthi dichotomi Radices, Parmeliae herba of moss, Pyrus baecate	Chinese medicinal composition	Badmajew, 1988
2.	Infusion in vinegar of Geum, Lavandula, Mentha, Allium, and Salvia	Cream	Pasini,1991
3.	Herba Chelidonii (Chelidonium majus)	Topical emulsion or ointment	Wendorff, 1992
4.	Allium sativum, Urtica dioica, Chelidonium majus, Veronica officinalis, Calendula officinalis, Achillea herba, Fumaria officinalis extracts	–	Horvath, 1993
5.	Et Hg thiosalicylate, plantain extract, rose extract, orange extract	Topical composition	Perez, 1993
6.	Arnica Herb, marigold, Fructus Rhodomyrti, Radix Hamamelis Mollis, Avocado	Medicinal ointment	Hasse, 2000
7.	Hong chan ji nu chong ji (Flos Lonicerae, Flos Chrysanthemi, Radix Glycyrrizae, Herba Taraxaci, Radix Angelicae Sinensis, Radix Polygalae, Cortex Dictamni, Herba Schizonepetae, Flos Carthami, Squama Manis, Herba Artemisiae Anomalae, Periostracum Cicadae, Radix Trichosanthis, Radix Saposhnikoviae, Scolopendra)	Chinese medicinal composition	Fu, 2000
8.	Rhizoma Smilacis Glabrae, head and foot of Mylabris, Radix Aconiti Kusnezoffii, Calomelas, Herba speranskiae tuberculatae, Fructus Quisqualis, Realgar, Scorpio, Camphora, Semen Arecae, Spina Gleditsiae, Herba Plantiginis, Borneolum Syntheticum, Chalcanthitum	Niupixuanjing (Chinese medicinal composition)	Mo, 2001
9.	Turmeric extract, α-hydroxy acids,α1-antitrypsin	Topical formulation (cream, lotion, salve, etc)	Phan, 2003
10.	Chamomile extract, olive oil, horsetail tincture, massage oil, arnica tincture, ribwort tincture, mallow tincture	Infusion drinks and ointment	Lange & Juergen, 2003
11.	Gan Jiang, Dan Shen, Jiang Xiang, Huang Qi, Gui Zhi and Cang Zhu	Capsule	Tang, 2004
12.	Mylabris, Calomelas, Indigo Naturalis, Scolopendra, Realgar, Herba Xanthii, Halloysitum Rubrum, Red mercuric oxide, Cortex Pseudolaricis tincture	External use traditional Chinese medicinal liquid	Wang & Wang, 2004
13.	Herba Schizonepetae, Notopterygii Rhizoma, Fructus Tribuli, Herba Spirodelae, Herba Taraxaci, Flos Albizziae, Flos Moutan, Herba Andrographitis, Flos Lonicerae, Glycyrrizae Radix	Chinese herbal tea	Huang & Huang, 2005
14.	Moisturizing cream, berberine, oleuropein, glucosamine	Cream	Meisner, 2005
15.	Vaseline as excipient (base), Hydrochloric Acid solution 37%, Boric Acid and Oil of Black Cedar	Ointment	Kapaj, 2005
16.	Mimulus aurantiacus extracts	Lotion, cream, salve, gel, lotion, foam, spray, soap, or shampoo.	Butler, 2005
17.	Mussel, Carnis Rapanae Thomasianae, Concha Ostreae, Concha Meretricis Seu Cyclinae, Liushugu, Scolopendra	Topical or oral composition	Gao, 2005
18.	Psorberine (M. aquifolium alcohol-water extract)	Topical formulation (ointment, cream, gel, shampoo, spray, powder etc)	Gomez, 2006
19.	Rosin extract (abietic acid) and adjuvants	–	Mi et al., 2006
20.	Extracts of Wrightia tinctoria, Ocimum sanctum, Azadirachta indica, Santalum rubrum, Acacia catechu	–	Thanikkal, 2008
21.	Extracts of Phellodendri Cortex and Rhizoma Coptidis	–	Seo et al., 2009
22.	Melia azadirachta Linn., Garden Balsam Stem, Fructus Zanthoxyli, Euphorbia nematocypha, Pseudolarix amabilis Rehd., Rumex japonicus Houtt., Rhododendron molle, Hydnocarpus anthelminthicus, Centipede Scolopendra, Asarum sieboldii, Angelica dahurica, Momordica cochinchinensis, Radix Cynanchi Paniculati, Cacumen Platycladi, Mylabris phalerata, Fibraurea recisa Pierre, oil of Flos Caryophylli, tea plant oil, oil of turpentine, cedar wood oil	Traditional Chinese medicine for external use	Zhou & Wang, 2008
23.	Radix Stemonae, Bletilla striata, Pericarpium zanthoxylum, Hydnocarpus anthelmenticus, Radix Aconiti kusnezoffii, sulphur, salicylic acid, ethanol	Chinese herbal medicine	Dang, 2008
24.	Non-aqueous herbal extract of Wrightia tinctoria and herbal extract of Cocos nucifera	Ointments, oils, soaps, shampoos	Reddy et al., 2008
25.	Spruce, Fir, Miquel Linden	Therapeutic herbal tea	Garneau, 2008
26.	Catechins from green tea	Lotion	Bettuzzi & Corvetta, 2008
27.	Mimosine and idebenone	Occlusive patch, cream, gel, emulsion, spray	Gabriel & Martin, 2009
28.	Junglans regia L.,Origanum vulgare L., Baccharis glutinosa, Thymus vulgaris L., Sambucus nigra L., Rosemarinus officinalis, Tropaeolum majus L., Saonaria officinalis L. aqueous extracts	Topical cream or shampoo	Sanchez, 2009
29.	Petroleum ether extracts of Wrightia tinctoria, Azadirachta indica and Hemidesmus indicus	Antipsoriatic and antidandruff drug (topical)	Pushpangandan et al., 2009
30.	Cimicifuga extract	o/w topical emulsion	Wuttke, 2009
31.	Purified Arabinogalactan Protein	Oral (tablets, capsules, elixirs) or topical (cream, ointment)	Arora et al., 2009
32.	Wrightia tinctoria oil extract	Hydrophobic topical formulation (cream, ointment)	Kanaujia et al., 2010
33.	Realgar, Radix Glycyrrhizae, Indigo naturalis, Radix et Rhizoma Rhei, Arnebia euchroma, Salvia miltiorrhiza, Herba Asari, Galla chinensis, Cinnamomum cassia ethanol extracts	Chinese medicinal topical composition	Gao, 2010
34.	Eruca, Nigella, Citrus medica, Hypericum extracts	Topical composition	Fulder et al., 2010
35.	Pandanus conoideus plant extracts	Topical preparation (microemulsion)	Susilo, 2010
36.	Extracts of Psoralea corylifolia, Luffa acutangula, Rubia cordifolia, Boswellia serrata and Brassica nigra and oils of Azhadirachta indica, Linum usitatissum, Vitis vinifera, Brassica nigra, and Pongamia seed	Herbal lotion, herbal cream	Babu & Mishra, 2011
37.	Agkistrodon, Bungarus fasciatus, Bungarus multicinctus, Piper wallichii, cobra, Schizophragma integrifolium, Cocculus trilobus, Schefflera arboricola, Caulis Spatholobi, Siegesbeckia orientalis, Rhododendron molle	Chinese herb textile	Cheng & Cheng, 2011

Figure 1.  Structures of phytoconstituents reported to possess antipsoriatic activity.

Conclusion

The medications used to treat psoriasis presently have a number of side effects, which has shifted the researchers’ attention to safer natural alternatives. PUVA therapy which is widely accepted worldwide for psoriasis treatment has active moiety psoralen derived from natural source, Psoralea corylifolia. Keeping in mind, severe side effects associated with synthetic drugs available for the treatment of psoriasis, herbal drugs seem to be a viable approach to explore for newer, safer and effective antipsoriatic drugs. Plants such as Curcuma longa, Aloe vera, and Thespesia populnea have been used in the traditional systems to offer relief in skin disorders like psoriasis, and proved scientifically for their traditional claims. Inclusion of such plant drugs in the arsenal of modern therapeutics has revived the faith of researchers in natural resources.

In the present review article, amongst 18 plants reported to possess antipsoriatic activity (Table 1):

• (a) Preliminary activity screening has been carried out on crude extracts of 12 plants. Such plants, viz., Aloe vera, Angelica dahurica, Betula alleghaniensis, Caesalpinia bonduc, Celastrus orbiculatus, Coptis chinensis, Mahonia aquifolium, Picea mariana, Rubia cordifolia, Saccharum officinarum, Tabebuia avellanedae and Thespesia populnea need to be explored with a view to isolate active constituents and to establish their mode of actions,

• (b) chemical constituents responsible for antipsoriatic activity have been reported in six plants,

• (c) only five plants have been tested clinically for antipsoriatic activity, and

• (d) possible mode of action has been reported for 8 plants.

Fifteen chemical constituents of plant origin responsible for antipsoriatic activity have been reported (Table 2) and 40 plant-based formulations from various systems of medicine including Chinese, Ayurvedic, and Unani have shown antipsoriatic activity (Table 3). Thirty-seven antipsoriatic formulations containing plants have been patented (Table 4).

It is anticipated that this review article will be of immense help to natural product researchers to select traditionally used plants with medicinal potential for their future research work.

Declaration of interest

The authors acknowledge the All India Council for Technical Education, New Delhi for providing financial assistance to Ms Arshdeep Kaur. The authors report no declarations of interest.