Chemical constituents and antimicrobial properties of Phyllanthus amarus (Schum & Thonn)

Abstract

The chemical composition of the leave extracts of Phyllanthus amarus (Schum and Thonn) of the family Euphorbiaceae from Nigeria was analyzed by GC-MS. The extracts were also examined for their potential to inhibit the growth of clinical isolates following standard procedure. The major compounds identified in the hexane extract are a flavonoid, flavone 4’,5,7-triethoxy-3,3’,6- trimethoxy (20.23%) and a triterpenoid 17-(1,5-Dimethylhexyl)-6-hydroxy-5-methylestr-9-en-3-yl acetate (19.02%) while bufalin (18.71%) and tetratetracontane (12.91%) were the major compounds detected in the methanol extract. Steroidal triterpenoids are the major compounds present in the extracts as it accounted for 47% of the total detectable content in the hexane extract and 52% in the methanol extract. The steroidal triterpenoids which exist primarily as acetate in the hexane extract include cycloeucalenyl acetate, ergosta-5,7,22-trien-3-ol acetate, macdougallin, 17-(1,5-Dimethylhexyl)-6-hydroxy-5-methylestr-9-en-3-yl acetate, stigmasterol and β-sitosterol while the methanol extract contains 6,7-epoxypregn-4-ene-9,11,18-triol-3,20-dione, 11,18-diacetate, bufalin, olean-13(18)-ene, methyl ursolate, barringenol R1 and 7,8- epoxylanostan-11-ol,3-acetoxy. Hexane extract of the plant exhibited antifungal activity on Candida albicans while methanol extract revealed significant antibacterial activity on Pseudomonas aeruginosa and Staphylococcus aureus at all concentrations of the extract between 12.5 and 100 mg/mL, the activity being comparable to the standard antibacterial drug, Oxacillin. The leaves of Phyllanthus amarus is a potential source of steroidal triterpenoids which could serve as biomarker for the plant species. The extracts of the plant may also serve as a natural source of antimicrobial agents for the treatment of some microbial infections.

Keywords: Phyllathus amarus, antimicrobial, phytochemicals, leaf extracts