Phytochemical investigation and antimicrobial activity of laportea aestuans (L) chew.
The study obtained the crude extract of the aerial part of L. aestuans and developed an effective chromatographic procedure for the fractionation of the most active extract; it evaluated, isolated and characterized constituent(s) for antimicrobial activity. This was with a view to providing scientific information and justification for some of its ethnomedicinal uses. The collected aerial part of L. aestuans was authenticated at the Herberium Unit of the Department of Pharmacognosy, Obafemi Awolowo University, Ile-Ife with Voucher specimen (No. FPI 1884), air-dried, powdered and extracted with three organic solvents [acetone (100%), dichloromethane:methanol (1:1) and methanol:water (1:1)]. Each of the three extracts was subjected to antibacterial screening against Escherichia coil (ATCC 25922), Staphylococcus aureus (NCTC 6571), Pseudomonas aeruginosa (ATCC 10145) and Bacillus subtilis (NCTC 8236) using the agar well diffusion method. The crude extract was fractionated on open column liquid chromatography using silica and Sephadex LH-20 and the isolated pure compounds were characterized using resonance spectroscopic techniques. The results obtained revealed that each of the acetone (100%), dichloromethane:methanol (1:1) and (1:1) aqueous methanol extracts of L. aestuans had a narrow antibacterial spectrum against all the tested organisms. The three extracts had almost the same zone of inhibition against B. subtilis. Minimum Inhibitory Concentration (MIC) of the 50% aqueous methanol extract was MIC 650 μg/ml against B. subtilis followed by 100% acetone (MIC 1250 μg/mI) and dichloromethane:methanol (MIC 2500 μg/ml) extracts when compared to Streptomycin sulphate (MIC 3.91 μg/mI). The chromatographic fractionation resulted in the isolation of two compounds LAF3F2B (1) and LAF3B3A (2). However, LAF3F2B (1) was characterized as methyl 2-(hydroxymethyl)-4-(5-(1, 2-dimethoxyethyl) morpholin-3y1) butanoate (1) which interestingly is being reported for the first time from Laportea aestuans. The study concluded that the plant, Laportea aestuans possessed antibacterial activity against B. subtilis.