Antibacterial activity of water extracts of different parts of Morinda citrifolia grown in Sri Lanka

Abstract

This study examined the antibacterial potential of water extracts of different parts of Morinda citrifolia (Family: Rubiacae) plants which is used/indicated in Sri Lankan traditional and folk medicine to wash old cutaneous wounds, cuts, abrasion, rashes, bruises or burns, and as a throat gargle. This was tested in triplicate, in vitro, using agar disc diffusion bio assay against Gram positive human pathogenic bacteria, Staphylococcus aureus (ATCC 25923) and Gram negative bacteria , Escherichia coli (ATCC 35218). Concentration of water extracts tested were 500,750 and 1000 µg/disk. Gentamicin (10 µg/disk) was used as the positive control. The results showed that none of the extracts (roots, fruits, flower, stem bark or combination of these parts) was effective against E. coli whilst fruit (diameter of inhibition zone 2.93 ±0.03mm), stem bark (5.1 ±0.03mm) and combined extract (9.46 ± 0.03mm) exhibited antibacterial activity against S. aureus. The reference drug, Gentamicine induced an inhibition zone of 13.98 ±0.04mm against S. aureus and 15.02 ±0.03 mm against E. coli. It is conducted that water extracts of different parts of M. citrifolia plant has mild to moderate antibacterial activity against S. aureus, a commonly encountered pathogen in cutaneous wounds. In addition, the results justify its use in Sri Lankan ethnomedicine as a topical cleaning agent for infected skin wounds.