Bioassay-guided investigation of Lonchocarpus cyanescens benth leaves extracts for antioxidant activities

Abstract

Antioxidants have been reported to prevent oxidative damage caused by free radicals and can be used to ameliorate conditions in cardiovascular and inflammatory diseases. Ethnobotanical study revealed that the leaves of Lonchocarpus cyanescens are traditionally used in Africa to treat ulcer and arthritis. This study investigates the antioxidant activities of its extract and fractions. Acetone leaf extract of L. cyanescens was screened for 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity, ferric reducing power (FRAP), total phenol content and total flavonoid content using catechin as standard antioxidant. Bioguided column chromatographic separation was carried out and the resultant fractions were screened for antioxidant activities. Preliminary spectroscopic profile of the most active fraction was obtained. DPPH and FRAP methods showed that L. cyanescens had antioxidant activity which correlated with its phenolic and flavonoid contents. There was a higher correlation of the total phenol/flavonoid content to the antioxidant activity by the DPPH method [r2 = 0.9906, 9926 respectively] than the FRAP method [0.8635, 8840 respectively]. Bioactivity guided fractionation identified fraction F5 as the most active. ¹H and Infrared spectra indicated that the most active fraction contained flavonoids. Comprehensive in-vivo studies and toxicity profile of the extract will be required before considerations for development as a phyto-drug.

Keywords: Lonchocarpus cyanescens, antioxidant, DPPH, FRAP, phenol, flavonoid

African Journal of Biotechnology, Vol 13(22) 2240-2247