Antimicrobial and antioxidant activity of the methanolic extract of Alpinia purpurata rhizomes

Abstract

The present study was undertaken to determine antimicrobial and antioxidant activities of the methanolic extract of rhizomes of Alpinia purpurata. Antimicrobial activity was tested against Escherichia coli (MTCC 25922), Enterococcus aerogenes (MTCC 29212). Pseudomonas aeruginosa (MTCC 27853), Staphylococcus aureus (MTCC 25923) and Proteus vulgaris (MTCC 7299) by disc diffusion assay method. Antioxidant activity was determined by DPPH free radical scavenging assay. The rhizomes of Alpinia purpurata exhibited significant antioxidant inhibitory activities with an 93.82% and 88.56% respectively at the concentration 80 µg/ml and 100 µg/ml and well compared with standard ascorbic acid drug. As the concentration of rhizomes of Alpinia purpurata increased from 20-100 µg/ml, the inhibitory actions of the Alpinia purpurata increased towards all the strains used in this study. At concentration 100 µg/ml, the rhizomes of Alpinia purpurata exhibited the antimicrobial activity all the five bacteria and five fungal pathogens, but was more susceptible against Escherichia coli (20 mm), Staphylococcus aureus (19 mm) at concentration 100µg/ml., followed by the highest activity against Aspergillus flavus and Candida albicans (10 mm zone of inhibition) at 100 µg/ml, followed by the highest activity against Aspergillus niger, Candida vulgaris and Candida tropicalis (9 mm zone of inhibition). The result confirms that the rhizomes of Alpinia purpurata antibacterial and antifungal activity against the tested bacteria.