Antimicrobial activity of supercritical fluid extracts of two Philippine medicinal plants, Psidium guajava and Euphorbia hirta: Implications to community health

The study is aimed to determine the antimicrobial activity of supercritical crude extracts of Psidium guajava and Euphorbia hirta against four bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and the two fungi namely, Aspergillus niger and Candida albicans. Fresh leaves of P. guajava and whole plant of E. Hirta were extracted using Supercritical Fluid Extraction at 120 atm with supercritical CO2 as the extracting solvent. Antibacterial activities of the crude extracts against the six microorganisms were determined by Filter Paper Disc method. Results showed that the crude extracts of the two plants exerted vary degrees of inhibition to the six test microorganisms. P. guajava exerted pronounced inhibitory action against the gram-positive bacteria (B. subtilis and S. aureus) but minimal against the gram-negative species (E. coli and P. aeruginosa) and fungi (A. niger and C. albicans). E. Hirta extract showed weak bacterial activity against all test microorganisms. Comparison in the antimicrobial activities between these two plants revealed P. guajava to be much stronger than E. Hirta but only against gram-positive bacteria while both plants have the same minimal inhibitory effect against gram-negative and fungi species. Further, P. guajava extract showed stronger bactericidal effect against gram-positive bacteria when compared with the standard antibiotic chloramphenicol which may scientifically validate its effectiveness as alternative herbal remedies to treat ailments common in rural areas. The weak antimicrobial and antifungal actions of E. hirta demonstrated in our study may further point to the plant’s other medicinal value such as plateletincreasing effect as reported by some authors.