Anti-inflammatory and antioxidant activities of the fruits of vitex doniana (hort. Brit.) And the quantification of one of its bioactive constituents oleanolic acid

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APRIL, 2019
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Inflammation is associated with virtually all diseases with oxidative stress being implicated in its complications. Nature has offered a number of clinically useful antiinflammatory agents and also affords a plethora of antioxidants. Vitex doniana fruit, a delicacy of some tribal groups in Northern Ghana, has not been investigated for its beneficial effect although it is used ethno medically in the treatment of various inflammatory conditions. Therefore the present studies aimed at evaluating the fruits for its antioxidant and anti-inflammatory activities and constituents as well as its toxicity. The dried pulverised fruit was extracted with methanol and subsequently partitioned to obtain pet-ether, ethyl acetate and methanol soluble fractions. The methanol fruit extract and subsequently its petroleum ether, ethyl acetate and remaining methanol soluble fractions were evaluated for anti-inflammatory and antioxidant activities using the chick carrageenan anti-inflammatory assay and three antioxidant assays; DPPH radical scavenging, ferric reducing power and total antioxidant capacity. In the antiinflammatory assay using 7-day old chicks, the extracts and fractions were dosed at 30, 100 and 300 mg/kg body with dexamethasone (0.1, 0.3, 1.0 mg/kg) and diclofenac (10, 30, 100 mg/kg) used as reference drugs. The foot volumes were measured using a digital caliper for 5 hours. The acute and subacute toxicity studies of the crude extract dosed at (100, 300 and 3000 mg/kg) and (100, 300 and 1000 mg/kg) respectively were also evaluated. All extracts demonstrated dose-dependent anti-inflammatory activity with the methanol soluble fraction exhibiting the highest activity (ED50 = 16.52 ± 4.65 mg/kg) followed by ethyl acetate (ED50 = 19.17 ± 2.89mg/kg) and pet ether respectively. The ED50 values for dexamethasone and diclofenac were 7.19 ± 4.91 and 7.55 ± 1.09 mg/kg respectively. The ethyl acetate fraction showed the highest antioxidant activity with IC50v value of 99.35 ± 0.77 µg/mL for the DPPH radical scavenging assay and a gallic acid equivalence (GAE) of 58.22 ± 3.66 mg/g in the total antioxidant capacity assay. LD50 by oral route was estimated to be beyond 3000 mg/kg. No signs of autonomic and CNS stimulation/depression were recorded. Subacute studies revealed an increase in haematological parameters (RBCs, HB PCV) as well as lymphocyte counts. Liver enzymes (ALT, AST, ALP and GGT), serum proteins and bilirubin levels were not increased. Chromatographic investigation of the active ethyl acetate fraction yielded compounds VDF-1, 2 and 3 of which the structure of the former was elucidated as 3β- hydroxyolean-12-en-28-oic acid (oleanolic acid). Oleanolic acid and the other compounds showed significant anti-inflammatory and antioxidant activities and contributed to the respective activities displayed by the crude extract. The content of oleanolic acid in the crude extract was determined to be 84.15 mg/g using a validated HPLC method. The results obtained indicate that the methanol fruit extract of V. doniana possesses considerable anti-inflammatory, antioxidant and possible immunomodulatory activities and that high performance liquid chromatography (HPLC) remains an essential tool in the quality control of natural products
A thesis submitted to the Department of Pharmacognosy, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirements for the Award Degree of Master of Philosophy in Pharmacognosy.
Anti-inflammatory, Antioxidant activities