Phytochemical Contents and In Vitro Pathogenic Microbial Growth Inhibitory Activities of Acanthus montanus Root and Leaf Extracts

Abstract

The study was directed at extraction, bioactivity analysis and ascertaining phytochemical composition of the leaf and root extracts of Acanthus montanus. Acanthus montanus (Acanthaceae family) is a shrub that is popularly grown in tropical countries of the world. The plant materials were harvested from Choba community in Rivers State, Nigeria. Extracts of Acanthus montanus (28.3, 19.45 and 25.5 g of n-hexane, ethylacetate and ethanol leaf extracts; and 3.45, 11.32 and 12.44 g of n-hexane, ethylacetate and ethanol root extracts respectively) were obtained through sequential maceration and were separately subjected to in vitro bioassay against a wide range of pathogenic microbes using the agar well diffusion method. Fifteen microorganisms were employed in the investigation, eight bacteria which included Salmonella typhi, Salmonella paratyphi, Pseudomonas aeruginosa, Shigella sonniea, Shigella dysentariae, Escherichia coli, Staphylococcus aureus, Staphylococcus pyogenes and seven fungi which included Candida albicans, Sacharomyces cerevisiae, Rhizopus eligastus, Aspergillus flavus, Aspergillus fumigates, Fusa equisetti and Aspergillus niger. The crude extracts exhibited high microbial growth inhibitory activities with zones of inhibition which ranged between 14 and 34 mm, though there was moderate (19 mm zone of inhibition), or no activity observed for the n-hexane leaf and root extracts. All test organisms were sensitive to the extracts. Standard analytical methods and Gas Chromatography - Flame Ionization Detector (GC-FID) were used for analysis and quantification of the phytochemicals present in the extracts. Major phytochemical contents of the leaf and root extracts included flavonoids (86% - 52.66%), alkaloids (10.66% - 3.25%) and other phenolic compounds (20.52% - 6.38%). In conclusion, the leaf and root extracts of Acanthus montanus are broad-spectrum antimicrobial agents also rich in flavonoids.