ABSTRACT
A methanol extract of the stem bark of Chlorophora excelsa. (Welw.) Benth and Hook was evaluated for anti-inflammatory activity in different models. Acute inflammatory effects were studied in the carrageenan-induced rat paw edema, and the effect of the extract in chronic inflammation was evaluated using the cotton pellet granuloma test. The effect of the extract on topical inflammation induced with croton oil was also tested in mice. The extract produced a significant (p < 0.05) and dose-dependent inhibition of the carrageenan-induced pedal edema, as well as granuloma tissue formation in rats. Topical anti-inflammatory effect was only evident with 400 mg/kg of the extract. This study demonstrated acute, chronic, and topical anti-inflammatory properties of the methanol extract of C. excelsa..
Introduction
Chlorophora excelsa. (Welw.) Benth and Hook is a large tall tree, growing to about 60 m high. It belongs to the family Moraceae. It is also known as the African oak and popularly referred to as the “Iroko tree” in the southwest of Nigeria.
The plant has been employed in West Africa over many years, in spite of its popularity as a mystical tree. The plant parts are used in cough associated with bronchitis, venereal sores, and as an antibacterial. The plant also finds application in fevers, lumbago, and rheumatism (Oliver-Bever, Citation1986; Iwu, Citation1993).
In our first attempt at establishing the anti-inflammatory profile of the plant, a methanol extract of the stem bark was tested on carrageenan-induced rat paw edema, cotton pellet granuloma in rats, and croton oil–induced ear edema in mice.
Materials and Methods
Plant material
Chlorophora excelsa. stem barks were collected from a tree growing around Amina Way, University of Ibadan campus, University of Ibadan, Nigeria. The plant sample was identified in the Department of Botany, University of Ibadan, where voucher specimens were kept.
Shade-dried, powdered material was extracted with methanol for 6 h in a Soxhlet extractor. Solvent removal afforded the solid extract (yield: 8.4%). The extract was stored in a dessicator and prepared fresh in 0.9% saline for pharmacological studies.
Animals
Male Swiss mice (20–25 g) and male Wistar rats (180–210 g) were used. The animals bred and housed under normal laboratory conditions of humidity and temperature and light (12 h day:12 h night). They were allowed free access to drinking water and animal pellets. The Principles of Laboratory Animal Care (NIH Publication No. 85–23) guidelines and procedures were used in this study (NIH, Citation1985).
Carrageenan-induced rat paw edema
To test the effect of the extract on acute inflammation, the method described by Winter et al. (Citation1962) was used. Carrageenan suspension (0.1 ml, 1%) was injected in the right hind paw of each rat under the subplantar region. Rats were orally administered with the extract (100–400 mg/kg) 1 h before carrageenan injection. Control rats received an equal volume (10 ml/kg) of saline, and indomethacin (5 mg/kg) was used as standard drug. Increase in linear paw circumference was taken as a measure of edema (Hess & Milonig, Citation1972; Olajide et al., Citation1999).
Cotton pellet granuloma formation in rats
Sterile cotton pellets were implanted subcutaneously in the groin region of rats (Olajide & Alada, Citation2001). Animals then received the extract (100–400 mg/kg), hydrocortisone (15 mg/kg), or saline (10 ml/kg) orally once a day for 7 consecutive days. On the eighth day, the rats were sacrificed and the cotton pellet was removed, dried for 18 h at 60°C, and weighed (Olajide et al., Citation1998).
Croton oil–induced mouse ear edema
Mice were anesthetized with ketamine. Thereafter, croton oil (5 µg/ml) and the extract (10–40 mg/ear) were applied to the inner surface of the right ear of each mouse. The left ear was untreated. Control animals received only croton oil, and indomethacin (100 µg/ear)served as a reference. The animals were sacrificed 6 h later and 6-mm plug removed from both the treated and the untreated ears. The difference in weight between the two plugs was taken as a measure of edematous response (Zitterl-Eglseer et al., Citation1997).
Statistical analysis
Values are represented as mean ± SEM. Statistical significance was determined using the Student's t.-test; values with p < 0.05 were considered significant.
Results and Discussion
The methanol extract of C. excelsa. exhibited anti-inflammatory effect by producing significant (p < 0.05) and dose-dependent inhibition of the carrageenan-induced rat paw edema 3 h after carrageenan injection. Development of edema formation was inhibited by 37.0%, 44.1%, and 56.7% with 100, 200, and 400 mg/kgof the extract, respectively. At 5 mg/kg, indomethacin, a nonsteroidal anti-inflammatory drug, inhibited edematous response in rats by 72% ().
Table 1.. Effect of the methanol extract of Chlorophora excelsa. on carrageenan-induced rat paw edema.
The inflammatory granuloma is a typical feature of established chronic inflammatory reaction (Spector, Citation1969). The cotton pellet granuloma method is used to evaluate the exudative and proliferative components of chronic inflammation. The dry weight of the pellets correlates well with the amount of granulomatous tissue (Swingle & Shideman, Citation1972). shows that at all the doses studied, the extract of C. excelsa. exhibited significant (p < 0.05) and dose-dependent reduction of dry weight of cotton pellets.
Table 2.. Effect of the methanol extract of Chlorophora excelsa. on cotton pellet granuloma in rats.
The croton oil test has a good predictive value for screening compounds and extracts for topical anti-inflammatory activity. shows that C. excelsa. extract (400 mg/kg) produced significant inhibition of ear edema with topical application of croton oil, an inflammatory irritant. This result suggests the potential topical anti-inflammatory property of the plant.
Table 3.. Effect of the methanol extract of Chlorophora excelsa. on croton oil–induced ear edema in mice.
This study confirms the use of Chlorophora excelsa. in traditional medicine for various inflammatory conditions. We are in the process of studying further the anti-inflammatory property of the plant with the aim of elucidating the mechanism(s) involved in this action.
References
- Hess SM, Milonig RC (1972): Assay for anti-inflammatory agents. In: Lepow IH, Ward PA, eds., Inflammation, Mechanisms and Control. New York, Academic Press, pp. 1–12.
- Iwu MM (1993): Handbook of African Medicinal Plants. Boca Raton, CRC Press, pp. 150–151.
- NIH (1985): Guide for the Use of Laboratory Animals. DHHS, PHS, NIH Publication No. 85-23 (1985 Revised). Bethesde, MD, National Institute of Health.
- Olajide OA, Alada ARA (2001): Studies on the anti-inflammatory properties of Entada abyssinica.. Fitoterapia 72: 492–496. [PUBMED], [INFOTRIEVE], [CSA]
- Olajide OA, Awe SO, Makinde JM (1998): Analgesic, anti-inflammatory and antipyretic effects of Bryophyllum pinnatum.. Fitoterapia 69: 249–252. [CSA]
- Olajide OA, Makinde JM, Awe SO (1999): Effects of the aqueous extract of Bridelia ferruginea. stem bark on carrageenan-induced oedema and granuloma tissue formation in rats and mice. J Ethnopharmacol 66: 113–117. [PUBMED], [INFOTRIEVE], [CSA], [CROSSREF]
- Oliver-Bever B (1986): Medicinal Plants in Tropical West Africa. London, Cambridge University Press.
- Spector WG (1969): The granulomatous inflammatory exudates. Int Rev Exp Path 8: 1–55. [PUBMED], [INFOTRIEVE], [CSA]
- Swingle KF, Shideman FE (1972): Phases of inflammatory response to subcutaneous implantation of cotton pellet and other modifications by certain anti-inflammatory agents. J Pharm Exp Ther 188: 226–234. [CSA]
- Winter CA, Risley EA, Nuss CW (1962): Carageenan-induced oedema in hind paw of the rat as an assay for anti-inflammatory drugs. Proc Soc Exp Biol and Med 111: 544–547. [CSA]
- Zitterl-Eglseer K, Sosa S, Jurenitsch J, Schubert-Zsilavecz M, Della-Loggia R, Tubaro A, Bertoldi M, Franz C (1997): Anti-oedematous activities of the main triterpendiol esters of marigold (Calendula officinalis. L.). J Ethnopharmacol 57: 139–144. [PUBMED], [INFOTRIEVE], [CSA], [CROSSREF]