Chemical constituents, anti-inflammatory, anti-oxidant and antimicrobial activities of the stem bark and leaves of Ficus Exasperata (VAHL)

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The work presented in this thesis involves the scientific investigation of the traditional uses of the leaves and stem bark of Ficus exasperata Vahl (Moraceae) as an anti-inflammatory, analgesic and wound healing agent. It also describes the isolation and characterization of the active principles from the Ficus exasperata. The petroleum ether, chloroform, ethyl acetate and 70% ethanolic extracts of the leaves and stem bark were assessed for anti-inflammatory, antioxidant and anti-microbial activities. The anti-inflammatory activities of the extracts and isolates were investigated using the carrageenan – induced foot pad eodema model in seven – day old chicks. The extracts were given orally to the chicks at 30, 100 and 300 mg/kg body weight, 1 hour after induction of oedema with carrageenan. Diclofenac and dexamethasone were used as reference drugs and the foot volume measured by water displacement plethysmography for five hours. All extracts exhibited anti – inflammatory effect with the stem bark showing the highest activity (ED50 = 50.65± 0.012). Antioxidant properties of the extracts were investigated using five assays; total antioxidant capacity, total phenolic content, DPPH scavenging activity, reducing power and lipid peroxidation activity. The most active antioxidant extract was the stem bark with IC50 values of 42.27±0.012, 20.09±0.001 and 61.80±0.001 µg/ml for the lipid peroxidation, DPPH scavenging and reducing power assays. The respective values for the standard antioxidant compound n-propyl gallate were 73.54±0.014, 10.8±0.002 and 66.88±0.002 µg/ml. Antimicrobial evaluation of extracts at concentrations of 10 mg/ ml was done using the agar well diffusion and micro-dilution assays. Seven organisms; P. aeruginosa, S. typhi, K. pneumoniae, E. coli, B. subtlilis, S. aureus and C. albicans were used. The chloroform extract of the stem bark was the most active with MIC of 1000 µg/ml against P. aeruginosa and S. aureus. Bergapten, oxypeucedanin hydrate and sitosterol-3-O-β-D-glucopyranoside were isolated from the bioactive chloroform extract of the stem bark whereas β-sitosterol and sitosterol-3-O-β-D-glucopyranoside were isolated from the pet-ether and ethyl acetate extracts of the leaves. To the best of our knowledge, this is the first report of the isolation of these compounds in Ficus exasperata. They exhibited dose-dependent anti-inflammatory activities with ED50 values of 101.6 ± 0.003, 126.4 ± 0.011, 275.9 ± 0.012 and 123.4 ± 0.033 mg/kg body weight for bergapten, oxypeucedanin hydrate, sitosterol-3-O-β-D-glucopyranoside and β-sitosterol respectively. They also showed significant DPPH scavenging effect with IC50 values of 63.38 ± 0.010, 46.63 ± 0.011, 220.3 ± 0.031 and >1000 µg/ml for the respective compounds. In the antimicrobial assay, β-sitosterol and its glucoside were inactive against all the organisms. Bergapten and oxypeucedanin hydrate gave MIC’s >1000 µg/ml against all susceptible organisms. They were the most active anti-inflammatory, anti-oxidant and antimicrobial compounds. The results of these studies have demonstrated that extracts of the leaves and stem bark of F. exasperata possess anti-inflammatory activity and also display antioxidant and antimicrobial activities. These findings provide scientific justification for the use of the stem bark and leaves of F. exasperata Vahl, in various traditional medicines, for the treatment of inflammatory and infectious conditions.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Doctor of Philosophy, 2012