Phytochemical and Antimicrobial Analysis of Stem Bark Extracts from indigofera Arrecta hochst Ex A. Rich (Fabaceae)

Abstract

The aim of this work was to investigate the claimed of indigofera Arrecta hochst plant as ethnomedicinal uses. The stem bark of Indigofera arrecta was thoroughly extracted with methanol and concentrated in a vacuum using a rotary evaporator at 40°C. The extract was then partitioned to produce soluble extracts of n-hexane, ethyl acetate, chloroform, and methanol. General phytochemical screening of these fractions showed the presence of secondary metabolites like cardiac glycosides, steroids, terpenes, flavonoids, and tannins. The antimicrobial activity against S. aureus, S. pyogenes, S. faecalis, S. typhi, E. coli, C. ulcerans, P. vulgaris, and C. albicans was evaluated using tube dilution and agar diffusion methods as per NCCLS guidelines. The antimicrobial activity results, indicated by the zones of inhibition, ranged from 20 mm to 40 mm for the n-hexane extract, 16 mm to 21 mm for the ethyl acetate extract, and 20 mm to 27 mm for the methanol extract. The MIC values for the n-hexane, ethyl acetate, and methanol extracts ranged from 7.5 mg/ml to 15 mg/ml. The MIC of 15 mg/mL shown by the n-hexane extract against both gram-positive and gram-negative bacteria suggests a broad-spectrum activity of Indigofera arrecta. The n-hexane fractions underwent Column Chromatography using silica gel, resulting in 87 fractions, which were combined, based on thin layer chromatography analysis and recrystallized in methanol to produce a pure white crystalline powder that melts at 144°C. The structure of the isolated compound was determined through spectroscopic analysis and direct comparison with literature data, confirming it to be Stigmasterol (3β,22E-Sigmasta-5,22-dien-3-ol).