Antibiotic-potentiating activity, phytochemical profile, and cytotoxicity of Acalypha integrifolia Willd. (Euphorbiaceae)

Abstract

Acalypha integrifolia Willd. (Euphorbiaceae) (AI), an indigenous medicinal plant of the Mascarene Islands is traditionally used to manage infectious diseases. The authors aimed to evaluate the antimicrobial, antibiotic-potentiating activity and cytotoxicity of AI. Decoction as traditionally used and organic extracts (hexane, dichloromethane, ethyl acetate, and methanol) of AI leaves were screened for their antimicrobial activity against nine ATCC strains and 10 clinical isolates. A fractional inhibitory concentration index (FICI) was determined to establish any synergistic interaction between the extracts and antibiotics using the variable ratio analysis method. The phytochemical profile was established using chemical and thin-layer chromatography methods. The decoction and methanolic extracts inhibited the growth of all tested bacteria (minimum inhibitory concentration (MIC) ranged between 0.06–2.00mg/ml). The methanolic extract showed potent antibacterial activity against Escherichia coli (EC) (MIC: 0.06mg/ml), Pseudomonas aeruginosa (MIC: 0.50mg/ml), and Staphyloccocus aureus (SA) (MIC: 0.06mg/ml). The highest antibacterial activity was observed against clinical isolates of Enterococcus faecalis, S. aureus, and Methicillin-Resistant S. aureus (MRSA) (MIC: 0.50mg/ml). Moderate antifungal activity was observed against Candida albicans. Combination profiles of the extract with Ciprofloxacin, Chloramphenicol, and Streptomycin showed synergistic action (FICI≤0.50) against ATCC strains of EC and SA. Decoction and methanolic extracts showed low cytotoxicity against normal adult African green monkey kidney cells. Data obtained tends to corroborate with the reported traditional usage of the plant. Since the leaf decoction is traditionally used against skin infections as well as consumed for its astringent and purgative properties, the reported data tend to correlate with the low cytotoxicity as well as its anti-infective property. There may also be the potential towards the discovery of novel antimicrobial compounds.