Evaluation of phenolic contents , free radical scavenging activity and functional group analysis of the leaf extract of a medicinal plant in Niger Delta region

ISSN: 2410-9649 Amos-Tautua et al / Chemistry International 3(3) (2017) 250-257 iscientic.org. 251 www.bosaljournals/chemint/ editorci@bosaljournals.com heart diseases (Al-Dabbas et al., 2006). Diabetes is widely recognised as one of the leading causes of death and disability worldwide (American Diabetes Association, 2010). It is known to affect 3% on average of adult Nigerians (Akinkugbe et al., 1992). In humans, diabetes is normally associated with oxidative stress which gives rise to the generation of free radicals due to high levels of blood sugar (hyperglycemia) (Aruoma et al., 2007). Although these free radicals can be scavenged by the in vivo produced antioxidant compounds, the endogenous antioxidants are insufficient to completely remove them and maintain a balance. As a result, dietary antioxidants are required to counteract excess free radicals (Scalbert et al., 2005). Synthetic antioxidants, such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), which are effective in their role as antioxidants, are commercially available and currently used in industrial processes. However, since suspected actions as promoters of carcinogenesis and other side effects have been reported, their use in food, cosmetic and pharmaceutical products have been decreasing (Tepe et al., 2005). Thus, there has been an upsurge of interest in naturally-occurring antioxidants from vegetables, fruits, leaves, oilseeds, cereal crops, tree barks, roots, spices and herbs (Terashima et al, 2007). Many medicinal plants have now been recognised as sources of natural antioxidant and free radical scavenging compounds which are mainly phenolic compounds (Aruoma, 2003; Wangensteen et al., 2004). Funtumia africana (Benth.) Stapf belongs to the family Apocynaceae, which generally contains alkaloids (Gurib-Fakim, 2006). The plant which is known as Lagos Silkrubber in English, is a medium-sized forest tree up to 8-27 m in height; commonly composing in the second story of moist ever-green rain forests. The latex is used traditionally to treat incontinence and burns in West Africa (Wagner et al., 1987). The leaves of F. africana have been used by the people of Niger Delta region of Nigeria to treat diabetes. Given the implication of reactive oxidation species in many diseased conditions such as diabetes mellitus, neurodegenerative and cardiovascular diseases (Halliwell, 1991) and the possibility of polyphenolic compounds providing biological resistance against the destructive effect of free radicals, it was therefore worthwhile to estimate the possible antioxidant properties of F. africana. As far as our literature survey could ascertain there was no published information on the antioxidant activity of this plant species. This present study therefore aims to evaluate the in vitro free radical scavenging activities and polyphenolic contents of the methanol leaf extract and fractions from the plant using more than five antioxidant assays. MATERIAL AND METHODS Chemical and reagents All reagents used for antioxidant assays were of analytical grade bought from Sigma Aldrich. Collection of plant material The fresh leaves of Funtumia africana were collected from Amatolo town, Wilberforce Island, in the Niger Delta region of Nigeria. The plant was identified by Prof. K.A Ajibesin of the Department of Pharmacognosy and Herbal Medicine, Niger Delta University, Wilberforce Island, Nigeria. A voucher specimen (NDUP 112) of this collection has been retained at the Niger Delta University herbarium. Extraction procedure The powdered leaves of F. africana (100 g) were extracted with 20% aqueous methanol (1L) at room temperature for 24 hours and filtered. The filtrate was concentrated in vacuo at 400C to a small volume to give the crude methanolic extract (CME) which was partitioned into n-hexane (HEF), dichloromethane (DCF), ethylacetate (EAF) and n-butanol (BUF) fractions by solvent-solvent extraction technique. Qualitative phytochemical tests The preliminary phytochemical tests on the fractions were carried out using standard techniques described by Sofowora (1993) and Trease and Evans (2000).