Antimicrobial activity of compounds from Acanthospermum hispidum DC and Caesalpinia bonduc (L.) ROXB: Beninese plants used by healers against HIV-associated microbial infections

Abstract

In this study, we have tested alcoholic extracts (60%) from four Beninese plants: Ocimum gratissimum L., Acanthospermum hispidum DC, Caesalpinia bonduc (L) Roxb and Calotropis procera W. T. Aiton. They are used by the healers to prevent opportunistic diseases associated to HIV-AIDS; on six strains such as: Escherichia coli O 157H7, Staphylococcus aureus ATCC 25923 which resist to methicillin (MRSA), Salmonella typhi, Klebsiella pneumonia, Candida albicans ATCC 10231, and Mycobacterium bovis BCG 040812 which cause microbial infections associated with HIV-AIDS. The results show that all the extracts are bacteriostatic and fungistatic but only the hydro-ethanolic extracts of Acanthospermum hispidum (HE 2) and of Caesalpinia bonduc (HE 3) presented antibiotic power (respectively ap = 2 and ap = 4) on Candida albicans ATCC 10231. The Mycobacterium bovis BCG shown resistance to tested extracts (CMI > 250 μg/mL). The two fungicidal extracts HE 2 and HE 3 did not show harmful effects on the cells WI-38 with an IC 50 100 μg/mL for HE 2 and IC 50 = 50 μg/mL for HE 3. The successive bio-guided purifications of extracts HE 2 and HE 3 permitted isolation of three antibacterial compounds: Flavanone (M 1); stigmasterol (M 2); and quercetin (M 3). The three isolated compounds possess antibiotic power (ap 3±1) on tested strains and are not toxic on shrimp larvae (LC 50 : 0.30 ± 0.17 mg/mL).