Isolation, characterization and biological properties of betulin from Entada africana Guill. and Perr. (Mimosaceae).

Abstract

The present study is aimed at the isolation and characterization of betulin from Entada africana. A dichloromethane soluble portion of the stem bark methanol/acetone (1:1 v/v) extract was subjected to gradient elution using ethyl acetate in hexane (5 – 30 %) on an open column. A pure compound was obtained with Rf = 0.61 in hexane/ethyl acetate (8:2 v/v) after repeated washing and recrystallization from methanol and coded Enac1. The pure compound was analyzed using IR, 1H & 13C NMR and GC-MS. Clinical isolates of Escherichia coli, Klebsiella pneumoniae, Salmonella typhi and Staphylococcus aureus were used to assess the antibacterial activity of the pure compound while its preliminary Cytotoxicity was evaluated using brine shrimp nauplii. Based on the spectroscopic data obtained and in comparison with literature, the isolated compound was identified as betulin. The minimum inhibitory concentration (MIC) of betulin ranged between 62.50 - 250.00 µg/mL for all the four bacterial isolates in the study while its fifty percent lethal concentration (LC50) was 10.00 µg/mL. Significant Cytotoxicity with moderate antibacterial activity was observed. The study therefore justifies the existence of bioactive compounds in the stem bark of Entada africana and its use in traditional medicine.