Investigation of Phenolic Contents and TLC-Direct Bioautography Screening of Four Nigeria Plant Extracts for Antioxidant Activities

Abstract

In search of lead compounds with no side effect, four medicinal plants; Euadenia trifoliata, Lactuca capensis, Alstonia boonei and Ficus platyphylla were screened for antioxidant activity. Dried leaves of the four plants were extracted with EtoAc/MeOH (1:1) and the extracts obtained were screened by TLC-Direct bioautography method (TLC-DB) to identify the most promising extract from the four plants for antioxidant property. The TLC chromatogram revealed that the extract from the leaf of Euadenia trifoliata was the most promising and was thus fractionated into  dichloromethane, methanol and hexane soluble fractions. The fractions along with the crude extract were investigated for their phenolic contents and antioxidant potentials. Total phenolic content, TPCs, of the dichloromethane, methanol, crude and hexane extracts were 44.37, 28.83, 24.79 and 19.91 mg/g of gallic acid equivalents of extract, respectively. Antioxidant activities of the fractions using phosphomolybdate and free radical scavenging assays were in the order of methanol ˃ dichloromethane > crude ˃ hexane extract. The results of our finding indicated that methanol was the most suitable solvent to extract polyphenols and other antioxidant compounds from E. trifoliata leaves. In conclusion high polyphenols content of E. trifoliata leaves is an indication that the plant could potentially provide a remedy against disorders caused by oxidative stress.

Keywords: Antioxidant, Euadenia trifoliata, Phenolics, Radical, TLC-Bioautography