Antioxidant Activity of some Secondary metabolites from Tapinanthus bangwensis (Engl., and K. Krause) [Loranthaceae] Grown in Nigeria

The search for new natural antioxidants has grown tremendously over the years because reactive oxygen species (ROS) production and oxidative stress have been linked to a large number of human degenerative diseases, such as cancer, cardiovascular diseases and diabetes. Tapinanthus bangwensis, a parasitic plant commonly known as mistletoe is employed traditionally to treat cancer, diabetes and hypertension. In this study, air-dried pulverized leaves and stem of Tapinanthus bangwensis were successively extracted with n-hexane, ethyl acetate and methanol to give the corresponding crude extracts. The extracts were purified by column chromatography and high-performance liquid chromatography. Structural elucidation was done using mass spectrometry, Fourier transform infra-red, 1D and 2D NMR spectroscopy. Friedelin, eudesmic acid and methyl-3,4,5-trimethoxybenzoate were isolated and characterized. Friedelin was isolated from the ethyl acetate extract of the stem while the two other compounds were isolated from the methanol extract of the leaves. 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used to evaluate their antioxidant activity and ascorbic acid as standard. The percentage free radical scavenging activities of the compounds are as follows: Friedelin, 73.69, methyl-3,4,5-trimethoxybenzoate, 79.33 and eudesmic acid, 87.68 which were quite comparable to 93.96 given by ascorbic acid. To the best of our knowledge, the occurrence of friedelin and eudesmic acid in Tapinanthus bangwensis is being reported for the first time. The high antioxidant activity of these compounds supports the use of this plant in the management of diabetes and hypertension among other ailments. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.