MEDICINAL HERBS AS A SOURCE OF ANTIMICROBIAL SUBSTANCES

Abstract

This study aimed to test a variety of naturally occurring some medicinal herbs and their extracts for their antimicrobial potential against a group of some bacterial and fungal pathogens. A total of 6 herbs (Thymus vulgaris, Foeniculum vulgare, Datura stramonium, Matricaria chamomilla, Ammi visnaga and Cassia angustifolia). The antimicrobial activity of aqueous, methanol and petroleum ether extracts were evaluated by measuring the inhibition zone by agar well diffusion method and minimum inhibitory concentration (MIC) in order to increase the reliability and precision of the study. A number of 5 bacterial, 3 fungal and 1yeast species were chosen: G+ Bacteria: Staphylococcus aureus, Bacillis subtilis.G- Bacteria: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia. Fungi (molds): Aspergillus fumigatus, Penicillium italicum, Syncephalastrum racemosum, and (yeast): Candida albicans. The three different solvents gave markedly varied abilities to extract the antimicrobial compounds active against versatile groups including G+, G- bacteria and fungi. The active antagonism of crude methanolic extract can be descendingly arranged as Thyme> Senna> Fennel>Datura>Chamomile while the extract from Ammi vesnaga gave negative results. Methanolic extracts gave in MICs of 0.015-7.81 µg/ml (Thyme), 0.49 – 125µg/ml (Senna) and 31.25 – 500 µg/ml (Fennel) compared to MICs of 3.9 – 500 µg/ml, 31.25 – 500 and 15.63 – 500 µg/ml for those of ether extracts respectively in the same order of herbs. Essential oil and extracts of two herbs (Thymus vulgaris, Foeniculum vulgare), were analyzed by Gas Chromatography/Mass Spectrometry analysis which revealed the presence of 12 peaks in fennel essential oil indicating the presence of 12 phytochemical constituents representing 100% of the oil, while GC-MS analysis revealed the presence of 14 peaks in thyme essential oil which indicating the presence of 14 phytochemical constituents representing 99.98% of the oil.