Valorization of the phytochemical profile, nutritional composition, and therapeutic potentials of garlic peel: a concurrent review

ABSTRACT

Garlic (Allium sativum) is an ingredient that is frequently utilized in food for its therapeutic properties. Even though garlic peel accounts for 25% of production overall, unfortunately, it is discarded by the industry. Garlic peel is a valuable source of phytochemicals and medicinal substances. Throughout history, various civilizations have recognized the potential benefits of using garlic peel for illness prevention and treatment. This review emphasizes that garlic peel contains a variety of chemicals that are believed to offer health benefits for high blood sugar levels, lower the risk of cardiovascular illnesses, and have anti-tumor, anti-viral, anti-inflammatory, and anti-microbial properties. Additionally, we discuss the main bioactive substances in garlic peel, namely total phenolics, total flavonoids, and their derivatives. We may infer from our understanding that garlic peel is a useful agricultural waste because it contains a range of biologically active components. As a result, it can be employed as an ingredient to control health, especially in the biomedical and pharmaceutical fields.

KEYWORDS:

• Garlic peel
• phytochemicals
• antioxidants
• minerals
• phenolic acids
• neuroprotective
• anti-cancer

Introduction

Functional and nutraceutical meals are becoming more and more well-liked as a result of how important they are to enhancing health. The concept of diet-based therapies is helping to clarify the significance of traditional plants including garlic, ginger, black cumin onion, green tea, peanut, etc. Pakistan contains a variety of natural Phphytocoenosium plants. These plants are widely accessible, reasonably priced, and have other health-promoting properties. Due to their medicinal potential, a variety of fruits and vegetables, cereals, nuts, and legumes, among other foods, act as functional foods. They have a major role in the control of many metabolic processes, such as the removal of free radicals, antibacterial actions, and disease prevention^[1]. Allium sativum commonly known as Garlic, is regarded as a major vegetable because it is not only a required ingredient in cooking but also a delicious and healthy dish on its own.^[2] The allium genus shares the Liliaceae family with Asparagus, leeks, onions, and shallots. There are two varieties of garlic: A. ophioscorodon, a hard-neck species, and A. sativum, a soft-neck variation. Garlic possesses several secondary metabolites such as minerals and primary metabolites and has antioxidant properties.^[3] This plant has been used traditionally for both culinary and therapeutic purposes. It exhibits anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, antioxidant, cardioprotective, and immunomodulatory characteristics that can lower the risk of a wide range of illnesses.^[4]

Food waste has been noted as a global issue that contributes to food insecurity, particularly in middle-income nations, by the Food and Agriculture Organization (FAO). On a worldwide scale, it becomes a crucial concern to take advantage of food waste to increase food security and reduce the environmental crisis. Without considering its biochemical makeup and nutritional value, vegetable waste is discarded carelessly. Plant waste contains abundant macro and micro biomolecules which demands nutritional characterization of such waste for usage that can be used in the creation of novel nutritional recipes.^[5] Surprisingly, the skins of red onions, tomatoes, and sunflower seeds are rich in biomolecules such as flavonols, quercetin, diallyl sulfide, fructans, thiosulfinate, and anthocyanins as well as total sugars, protein, fiber, ascorbic acid, trace minerals, and essential amino acids.^[6,7]

The industry that processes garlic produces around 3.7 million tonnes of waste annually.^[8] Garlic cultivation yields extremely durable husks and straw that can be effectively transformed into a priceless biological resource. People are ignorant of its importance, so it is ignored or burned as a waste product in the modern garlic industry. It has recently become clear that it makes sense to use these resources wisely by adding value to support new by-products. Garlic peeling, which must be done before any further processing, is one of the most fundamental core procedures. The inedible, paper-thin, membrane-covered skin of the segmented garlic must be peeled off. Garlic bulbs generate about 760 g of cloves and 240 g of outer and inner peel per kg.^[9] As a result, there may be great promise for exploiting garlic byproducts as a rich biological resource that might be used to replace residues in a method that is efficient, affordable, and ecologically friendly.

Garlic peels contain six phenylpropanoids which are strong antioxidants.^[10] Moreover, the extract of garlic peel has antibacterial and antioxidant effects.^[11] It is also known to lower blood sugar levels following alloxan exposure in the animal model.^[6] The purpose of this review is to highlight the key ingredients present in garlic peel that can be used in improving the health status of human beings. We hope that garlic peel extract may one day be utilized as a natural food additive or possibly as a functional food due to its marvelous health-promoting properties (Figure 1). This can be materialized when proper extraction methods will be utilized to isolate all bioactive ingredients.^[12]

Figure 1. Phytochemical Profile of Garlic.

Source: (88)

Phytochemical profile

Whole garlic contains γ-glutamyl-S-allyl-l-cysteines. When whole garlic is cut/crushed, alliinase, an enzyme found in the cell wall, converts alliin into allicin and other thiosulfinates (diallyl disulfide (DADS), diallyl sulfide (DAS), diallyl trisulfide (DATS)). When garlic is extracted in an aqueous solvent γ-Glutamyl-S-allyl-l-cysteines are converted into water-soluble compounds including: S-allyl-cysteines (SAC).^[13]

Glutamyl-S-allyl-L-cysteine, allicin (diallyl thiosulfate), diallyl sulfide, and S-allyl-L-cysteine sulfoxide are sulfur-containing substances that are prevalent in garlic. These allium compounds regulate cholesterol, reduce blood pressure, and even lower some forms of cancer. The organic sulfur components of garlic are primarily responsible for its beneficial effects on health.^[1] Allicin is formed when the enzyme alliinase of bundle leaf cells reacts with the allin of mesophylic cells. It is a strong antibiotic, and antifungal agent and produces when A. sativum is crushed. However, due to its poor absorption, oral use of it is only minimally beneficial. Garlic contains vitamin B, proteins, minerals, saponins, and flavonoids as well as allixin (phytoalexin).^[8] There is a lack of alkaloids and the presence of saponins has been seen in the ethanolic or the aqueous garlic peel extract^[12]

Phenolic compounds

Similar to many other plant materials, garlic peels include a variety of phenolic compounds, which are natural antioxidants with a number of health advantages. The total phenolic contents of the garlic peel also have bacteriostatic and bactericidal effects. Further, these compounds are beneficial for plants to defend themselves from environmental challenges.^[12] Garlic peels contain a variety of phenolic chemicals, some of which have been listed below. Garlic peels contain significant amounts of alliin, a chemical that contains sulfur. It is a precursor to allicin, which is what gives garlic its distinctive odor.^[14] Alliin is transformed enzymatically by the enzyme alliinase to the sulfur-containing molecule known as allicin. It is a strong antibacterial and antioxidant substance that has been demonstrated to have a number of potential health effects.^[15] A class of phenolic chemicals known as flavonoids is abundantly present in plants. Antioxidant, anti-inflammatory, and anti-cancer effects have all been demonstrated in them. Garlic peels contain Quercetin, kaempferol, and rutin.^[16] Phenolic acids possess anti-inflammatory and antioxidant effects.^[17] Caffeic acid, ferulic acid, and p-coumaric acid are a few of the phenolic acids that have been found in garlic peels.^[10] These substances assist to lessen inflammation in the body since they have antioxidant capabilities.^[18] Garlic peels contain a chemical called S-allyl cysteine, which contains sulfur.^[19] It may help lower cholesterol levels and lower the risk of cardiovascular disease due to its anti-inflammatory and antioxidant qualities.^[20] Garlic peel and straw have a high lignin content, and extraction of significant components (phenolic compounds) is a great possibility. The major phenolic compounds found in garlic waste include P-coumaric acid, ferulic acid, diferulic acid, N-trans-coumaryl octopamine, dibutyl phthalate, 4-hydroxy-benzoic acid, 4-hydroxy-4-methoxy-benzoic acid, mequinol, and caffeic acid. Overall, the existence of these phenolic chemicals in garlic peels suggests that eating them may have a number of health advantages (Table 1). It’s crucial to keep in mind, though, that garlic peels aren’t typically consumed in most cultures and can be hard for some people to digest. Prior to making any big dietary changes, it is always advisable to speak with a healthcare expert.

Table 1. Bioactive substances derived from garlic peel extracts (dos Santos et al., 2022).

Extracts	Total Flavonoids (mg/100 mL)	Total Tannins (mg TAE/g)	Total Phenolic Compounds (mg GAE/100 g)	Total Anthocyanins (mg/100 mL)
EMAq	0.4820	434.33	3910.98	0.3157
EMH50%	0.9063	1003.02	12,022.35	1.3204
EMH70%	0.7604	1688.94	14,657.42	1.1711
ETH50%	0.7060	600.27	7945.28	0.1358
ETH70%	0.8859	833.55	6203.47	0.2885
ETAq	0.3768	486.21	4989.98	0.4956

GAE= Gallic Acid Equivalent. TAE= Tannic Acid Equivalent. EMAq= Aqueous maceration extract. EMH50%= Hydroalcoholic (50%) maceration extract. EMH70%= Hydroalcoholic (70%) maceration extract. ETH50%= Hydroalcoholic (50%) turbolization extract. ETH70%= Hydroalcoholic (70%) turbolization extract. ETAq= Aqueous turbolization extract.

Nutritional composition of garlic peel

Due to its possible health advantages and its use as an ingredient in foods, the nutritional makeup of garlic peel has been the focus of several studies. Garlic peel is an inedible byproduct of garlic. It has a moisture content of 3.52 ± 0.03%, a high protein content of 8.4 ± 0.41%, and a low lipid content of 0.86 ± 0.04%.^[8] The aforementioned findings were in line with other studies for other agro-industrial byproducts, such as dry soy husk (9% protein, 1% lipid) (Vriesmann et al., 2011) and cocoa husk (8.6% protein, 1.5%).^[21] The garlic peel has the highest percentage of total fiber (62.23 ± 1.03%). Dietary fiber was found to be 4.16% insoluble and 58.07% soluble, respectively. Both fenugreek husk (77.1%) and soy husk powder (74.41%) contained comparable amounts of total and insoluble fibers.^[8,22] The level of lignin in garlic peel (8.31 ± 0.12%) was likewise notable (Table 2).^[8]

Table 2. Nutritional Composition of garlic peel)^[23].

Parameters %	Garlic Peel
Carbohydrates (digestible)	8.5
Sugars (reducing)	1.36
Sugars (total)	6.51
Dry matter	80.8
Total ash	7.37
Water content	19.2
Total dietary fiber	62.10
Crude protein	2.61
Free fat	.22

Carbohydrates and lipids content in garlic peel

The weight of the garlic peel is roughly 26.58% total carbs and 18.62% cellulose.^[24] The peel of garlic contains a variety of sugars, including rhamnose, trehalose, mannitol, and sorbitol.^[25] According to reports, pectin (26–27%) is what makes garlic peel unique.^[26] The enzymatic hydrolyzate of garlic peel contains sinapic acid, ferulic acid, and p-coumaric acid.^[27] It also includes arabinose, xylose, rhamnose, mannitol, glucose, and galactose or their polymers. The majority of the overall sugar content is made up of rhamnose. It contains only trace amounts of lipids, with total sterols accounting for 62% of the unsaponified lipid fraction.^[28] The polysaccharides in garlic peel exhibited outstanding DPPH radical scavenging action, significantly reducing power, and inhibiting linoleic acid peroxidation.^[8,29]

Protein and amino acid profile of garlic peel

Protein

There are 67 proteins in both the inner and outer garlic peel. 43 of these proteins were located in the inner peel and 61 in the outer peel of the fruit. Between the two peels, 37 of these proteins were present, with 24 being unique to the outer peel and 6 to the inner peel. Biological process classification of the proteins revealed that only 9 of the 55 proteins were associated with reactions to stimuli, including chitinases, peroxidases, and heat shock proteins (HSPs). Eight proteins were identified as belonging to the serine and cysteine proteases.^[30] All 17 proteins involved in responding to stimuli and protein-modifying enzymes were found in the outer peel, with just 7 proteins present in the inner peel.^[25]

Amino acid

The order of amino acid concentrations in the garlic peel powder was observed as follows: Cys > Pro > Val > Tre > Arg > Ser > Trip > Ala > Tyr > Asp > Gly > Gl > Gl to-ta > Asp> Iso> His> Lei> Liz > Met > and so on.^[31,32] It contains the highest concentrations of tryptophan, glutamine, proline, cysteine, and arginine. In contrast, cysteine, proline, valine, threonine, and arginine are the amino acids that are most prevalent in garlic peel powder.^[33]

Mineral profile of garlic peel

Here is a detailed description of each mineral found in garlic peel; Calcium is necessary for developing and maintaining healthy bones and teeth, and is found in plenty in garlic peel. Additionally, calcium is essential for the health of your muscles, nerves, blood clotting, and cells. Garlic peel is a fantastic complement to a calcium-rich diet due to its high calcium concentration.^[20] Potassium: It is the second most common mineral in garlic peel and aids in controlling fluid balance, muscular contractions, and nerve messages. Additionally, consuming enough potassium helps lower blood pressure and lower the risk of stroke.^[34] Magnesium: It is necessary for maintaining healthy bones, nerves, and blood pressure regulation, and is abundant in garlic peel. Magnesium also contributes to the synthesis of DNA and protein, as well as the metabolism of energy.^[35] Sodium: Although a high salt diet is frequently linked to poor health results, the moderate sodium content of garlic peel is essential for maintaining fluid balance and nerve function.^[36] Sulfur: Garlic is renowned for having a high sulfur content, which is what gives it its distinctively strong smell and odor. The synthesis of proteins, enzymes, and other compounds in the body depends on sulfur.^[37] Iron: Garlic peel is a valuable source of iron despite having lesser concentrations of the mineral than certain other minerals. Hemoglobin, the protein in red blood cells that transports oxygen throughout the body, is produced only in the presence of iron.^[38] Manganese: This mineral is also essential for the growth of bones, the healing of wounds, and metabolism. Additionally, manganese serves as an antioxidant, assisting in preventing cell deterioration brought on by free radicals.^[39] Zinc: It is a vital mineral involved in a variety of physiological functions, such as immune response, wound healing, and DNA synthesis.^[40] Despite having less zinc than some other minerals, garlic peel is nevertheless a good source of this nutrient. Copper: It is essential for the production of red blood cells and the preservation of bone, neuron, and immune system function.^[41] Copper is present in garlic peel in a moderate proportion. Phosphorus: Garlic peel also contains phosphorus, which is necessary for DNA synthesis, energy metabolism, and bone and dental health.^[42] Selenium: A trace mineral called selenium has antioxidant qualities that can help prevent cell deterioration brought on by free radicals. Additionally, it influences thyroid and immune system health.^[43] Chromium: It is present in garlic peel and helps the body use carbohydrates, lipids, and proteins for energy, and is involved in controlling blood sugar levels.^[44] Aluminum: Many foods, including garlic and garlic peel, contain trace levels of aluminum, a naturally occurring metal.^[45] Even though garlic and garlic peel contain a little amount of aluminum, it is still safe to eat. However, it is important to take into account the possibility of aluminum toxicity from other food sources, such as cookware or antacids. However, consuming too much aluminum from other sources may have negative health effects, especially neurotoxicity and cognitive decline. Boron: The peel of the garlic contains traces of the trace element boron, which can be found in variable concentrations. Although boron may not be regarded as a significant mineral in garlic peel, it is crucial for plant growth and development (Table 3). Boron has been investigated for its ability to improve bone health, brain function, and immunological function in terms of human health. It may contribute to bone health by boosting bone mineral density and lowering the incidence of osteoporosis.^[46] Additionally, borax has immune-modulating properties and promotes the synthesis of cytokines and other immune system elements.^[47]

Table 3. Mineral Composition of Garlic Peel. Source^[23].:

Mineral	Garlic Peel (mg/kg)
Calcium	20610
Potassium	9081
Sulphur	1635
Magnesium	950
Aluminum	826
Phosphorous	721
Iron	682
Sodium	123
Manganese	35.4
Chromium	18.40
Boron	18
Zinc	12.9
Copper	2.09
Selenium	0.058

Biological properties of garlic peel

Antioxidant

Garlic peel was regarded as a useless waste product in the business, but numerous recent studies have shown that it contains potent antioxidant capabilities.^[47] It should be taken into account in the creation of disease-preventive products in the nutraceutical business. Flavonoids, organosulfur compounds, phenolic compounds, and vitamin C make up the majority of the bioactive components in garlic peel.^[48] An extract’s antioxidant capacity is evaluated using the DPPH radical scavenging action. An extract of garlic peels (ethanol) at a concentration of just 0.1% is shown to eliminate 90% of DPPH radicals.^[49] These results primarily attribute the antioxidant and antibacterial activities of garlic peel to the presence of the phytochemicals caffeic acid, p-coumaric acid, ferulic acid, and di-ferulic acid.^[10]

It contains significant levels of phenylpropanoids such as N-trans-coumaroyloctopamine, N-transferuloyloctopamine, guaiacylglycerol-ferulic acid ether, and coumaric acid, and ferulic acid,^[10] In an aqueous solution of garlic peel, gas chromatography mass spectrometry found the presence of dimethyl 2-methoxyhexane-1,6-dioate, dibutyl phthalate, 4-hydroxy-3-methoxy benzoic acid, 4-hydroxy-benzoic acid, and mequinol that had antimicrobial and antibacterial properties in addition to antioxidant properties.^[8] The total antioxidant content of garlic peel is 33.38 mg/ml which is indicated by the valorization of garlic peel for product development.^[50] This demonstrates the significantly high antioxidant activity of garlic peel. Additionally, the total flavonoid content of garlic peel is extremely high (33.27 mg Quercetin/ml), and flavonoids are well-known for their potent antioxidant properties.^[51]

Anticancer

The significant antioxidant activity that garlic peel exhibits are primarily responsible for its anticancer effects.^[52] Antioxidants scavenge free radicals, which lowers the risk of developing cancer. Even though the organosulfur level of garlic skins is lower than that of garlic cloves, they nevertheless possess anti-cancer capabilities. On the other hand, garlic skins have a substantially larger total phenolic content than cloves, which fundamentally alters the bioactive characteristics of peel.^[53]

Phenolic substances are thought to be effective anticancer agents. Because they have demonstrated significant promise in the treatment of cancer, such as via enhancing wound healing.^[54] Plant phenolics target metastasis, promote cell differentiation, inhibit uncontrolled cell proliferation, and promote apoptosis^[55] (S)-N-trans- feruloyloctopamine, which is derived from garlic skin, has demonstrated promising benefits in the prevention of skin cancers like melanoma.^[56]

Antidiabetic

An oral administration of a mixture of garlic peel and onion peel extract (800 mg/kg BW and 200 mg/kg BW, respectively) reduced blood sugar levels in both naturally occurring and induced diabetic rats, according to a rat study.^[57] Compared to the group receiving metformin and glibenclamide combination therapy, it demonstrated a good response, although there was no discernible difference from insulin therapy.^[58] The presence of significant bioactive components in garlic peel, including organoselenium, tellurium, flavonoids like kaempferol-3-O-b-D-glukopirosa and iso-ikamnetin-3-O-b-D-glukopirosa, fructopeptides, beta-carotene, thiamine, riboflavin, niacin.^[59]

Antimicrobial

Due to the presence of bioactive substances like allicin, alliin, and ajoene, garlic peel has been discovered to have antibacterial effects. These substances have inhibitory effects on a variety of harmful bacteria, fungi, and viruses. Garlic peel extract is effective against Bacillus subtilis, Listeria monocytogenes Staphylococcus aureus, Escherichia coli, Salmonella, Bacillus subtilis, Streptococcus mutans, and Staphylococcus aureus.^[60] Additionally, it possesses antifungal effects against Candida albicans and Aspergillus niger. It also shows antiviral properties against the respiratory syncytial virus (RSV) and herpes simplex virus type 1 (HSV-1).^[61] These findings support the antibacterial effects of garlic extract and its potential therapeutic uses in the management of drug-resistant microbial illnesses. In an in vitro setting, the antibacterial activity of various doses of garlic extract against the microbiota found in human dental plaque.^[62] This shows that using garlic extract instead of synthetic antibacterial medications may be a natural alternative for preventing and treating tooth plaque and related disorders like periodontitis. According to a study, ciprofloxacin and garlic extract work together synergistically, indicating that garlic extract could be used as adjuvant therapy for bacterial infections in addition to antibiotics.^[63] The absence of synergism between ampicillin and garlic extract, however, indicates that the antibacterial mechanisms of garlic extract may differ from those of several common antibiotics. It showed that a combination of garlic and ginger extracts had antibacterial action against clinical infections that were resistant to many drugs, including Pseudomonas aeruginosa.^[64] In order to prevent and treat microbial infections that are resistant to manmade antibiotics, this suggests that garlic and ginger extracts may have some value. Garlic may be a viable treatment for multi-drug resistant tuberculosis.^[65] This shows that garlic extract may have the potential as a natural substitute for common medications for treating and preventing tuberculosis and other bacterial infections that are resistant to common antibiotics. Overall, these investigations offer more evidence in favor of garlic extract’s antibacterial capabilities and its potential therapeutic uses in the prevention and treatment of bacterial infections, especially those that are resistant to traditional antibiotics.

Antiviral

Due to the presence of several bioactive substances such allicin, alliin, ajoene, and diallyl sulfides, garlic peel has been reported to have antiviral activities. Numerous viruses, including the RSV, HSV-1, influenza virus and human immunodeficiency virus (HIV), have been demonstrated to be inhibited by these substances.^[66] Although the exact mechanisms by which garlic peel exerts its antiviral effects are unknown, studies have shown that it may work by obstructing different phases of viral replication. For instance, it has been demonstrated that a garlic peel extract can prevent RSV and HSV-1 from adhering to surfaces and entering host cells. Inhibition of HIV’s reverse transcriptase function, which is necessary for the virus to replicate, has also been discovered. The immune-modulatory characteristics of garlic peel, in addition to its direct antiviral benefits, may help strengthen the body’s built-in defenses against viral infections. Activating the immune response against viral infections, for instance, may be made possible by the discovery that garlic peel stimulates the synthesis of cytokines and other immune system chemicals. The antiviral qualities of garlic peel point to its potential as a natural substitute for synthetic antiviral medications for a variety of medical uses, including the treatment of viral infections.^[2]

Anti-inflammatory

Due to the inclusion of several bioactive substances, including flavonoids, polyphenols, and organosulfur compounds, garlic peel has been discovered to have anti-inflammatory properties.^[67] Inflammatory mediators and enzymes, which play a role in the emergence of chronic inflammation, are inhibited by garlic peel. Interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β), among other pro-inflammatory cytokines, have been found in studies to be inhibited by garlic peel extract.^[68] Additionally, it blocks the action of enzymes including cyclooxygenase (COX) and lipoxygenase (LOX), which are crucial for the production of pro-inflammatory eicosanoids. The antioxidant properties of garlic peel extract potentially contribute to its anti-inflammatory effects. Free radicals and reactive oxygen species (ROS) can cause oxidative damage and set off inflammatory reactions. Antioxidants can scavenge these molecules. Garlic peel may be beneficial against arthritis, cardiovascular disease, and some malignancies.^[66,67] To find the best dosages and formulations for efficient anti-inflammatory activity in people, more research is nonetheless required.

Cardioprotective

Numerous bioactive substances, including flavonoids, polyphenols, and organosulfur compounds, which have been shown to have cardioprotective characteristics, have been discovered in garlic peel.^[69] These substances have been discovered to improve blood flow, lower blood pressure, and reduce cholesterol levels, all of which are good for cardiovascular health. Angiotensin-converting enzyme (ACE), which is involved in the control of blood pressure, is inhibited by garlic peel extract and lowers blood pressure. The mechanism of ACE inhibitor medications, which are frequently prescribed to treat hypertension, is comparable to this one. In animal tests, garlic peel extract has also been shown to lower levels of triglycerides, low-density lipoprotein (LDL) cholesterol, and total cholesterol.^[70] These effects could be brought about by the stimulation of cholesterol metabolism and excretion as well as the stimulation of cholesterol synthesis and absorption.

Neuroprotective

Furthermore, garlic peel extract increases nitric oxide (NO) production, a vasodilator that relaxes blood vessels and enhances blood flow.^[71] The blood pressure-lowering benefits of garlic peel extract may also be attributed to this mechanism. Numerous cardiovascular disorders, including hypertension, atherosclerosis, and heart disease, may benefit from the cardioprotective effects of garlic peel.^[72]

The aging population is prone to neurodegenerative illnesses, which result in the gradual degeneration and/or death of neurons. Although the molecular processes causing this degeneration are not fully understood, however, synaptic damage, mitochondrial malfunction, and protein misfolding are common in addition to neuronal loss. The progression of neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, stroke, and amyotrophic lateral sclerosis is significantly influenced by neuroinflammation. Neuroinflammation results in the activation of microglia, the innate immune cells of the central nervous system. Activated microglia can then release pro-inflammatory mediators, which in turn can cause oxidative/nitrosative stress and ultimately result in the death of neuronal cells. Many botanical preparations and substances with antioxidant capabilities have been studied in the search for efficient therapies for neuroinflammation and neurodegeneration.^[73]

The medicines that are available for these illnesses are not particularly effective. Interestingly, the improvement in medical care in the form of natural products has led to an increase in life expectancy. This encourages in treating age-related neurodegenerative illnesses, which pose significant social and financial burdens. Unfortunately, the great increase in life expectancy is masked by the decline in mental capacity with advancing age. The main underlying factor contributing to neurovascular injury is an increase in oxidative stress. Enhanced platelet aggregation and coagulation, endothelial dysfunction, hyperlipidemia, hypertension, ischemic heart disease, atherosclerosis, and hyperhomocysteinemia are additional risk factors for these illnesses.^[74].

A treatment approach called neuroprotection reduces the damaging effects on the brain. In order to prevent the negative effects of synthetic medications, recent developments in illness treatment favor the use of natural molecules.^[75] Garlic has been demonstrated to help prevent many chronic illnesses and ailments connected to aging since it is high in antioxidant chemicals and organic Sulphur. Phenolic chemicals with significant antioxidant and antibacterial activity are present in garlic husk. Garlic husk has enormous health advantages for individuals, thus it should be used in all its forms to improve people’s lives and prevent food from going to waste.^[76] The amino acid S-allyl-L-cysteine (SAC), which is found in garlic, has been linked to brain ischemia, Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and Huntington’s disease.^[77]

Garlic peel possesses neuroprotective qualities due to the presence of organosulfur compounds, flavonoids, and polyphenols.^[6] These substances have a number of positive impacts on brain health, including a decrease in oxidative stress, inflammation, and neuronal damage. By boosting the activity of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), garlic peel extract can lower oxidative stress in the brain.^[78] Free radicals and ROS can harm brain cells, thus this method can help prevent it. Garlic peel extract also exhibits anti-inflammatory actions in the brain.^[78]

Neurodegenerative illnesses, including Parkinson’s and Alzheimer’s disease (AD), have been linked to chronic inflammation in the brain. Garlic peel extract has neuroprotective properties against neuronal damage brought on by a variety of toxins and oxidative stressors. This extract shield brain cells from harm brought on by beta-amyloid protein in AD.^[79]

Hepatoprotective

Garlic peel exhibits hepatoprotective properties. Numerous positive benefits on liver health, including a decrease in oxidative stress, inflammation, and liver damage, have been linked to the presence of bioactive molecules of garlic peel. It decreases oxidative stress in the liver by boosting the activity of GPx, catalase, and SOD.^[80] By preventing the generation of pro-inflammatory cytokines and chemokines, garlic peel extract express anti-inflammatory actions in the liver.^[70] Non-alcoholic fatty liver disease (NAFLD) and hepatitis have been linked to chronic inflammation in the liver. Garlic peel extract possesses prevent liver damage brought on by numerous toxins and medications and shields liver cells from harm. This extract is also beneficial against liver cancer.^[81]

Conclusion

Garlic has long been used to treat and prevent different diseases due to its medicinal properties. In past, garlic peels are thrown away as waste despite research showing that they contain considerable levels of bioactive compounds. We discuss the medicinal advantages of garlic peel which are due to the presence of bioactive chemicals such as phenolic components including quercetin, kaempferol, rutin, and phenolic acids. Antioxidant, antibacterial, anti-cancer, anti-inflammatory, and antiviral characteristics are just a few of the health benefits of garlic peel. Garlic peel has the potential to be a useful alternative source in the creation of dietary supplements or functional meals for the treatment and prevention of cancer, neurodegenerative disease, diabetes, cardiovascular disease, and hepatic disorders. Based on our understanding, it can be concluded that garlic peel is excellent but needs to be treated carefully to completely enjoy its enormous medical advantages, keeping in mind that improper application may have unforeseen repercussions.

Consent to participate

All the coauthors are willing to participate in this manuscript.

Consent for publication

All authors are willing for publication of this manuscript.

Acknowledgment

Authors are thankful Government College University for providing literature collection facilities.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets generated used and/or analyzed during the current study available from the corresponding author on reasonable request.