Preliminary studies on chemical constituents and antimicrobial activities of Psidium guajava Linn

Guava is a phytotherapic plant used in folk medicine and it is having active constituents that help to treat and manage various conditions like malaria, vomiting, diarrhea and inflamed gums etc. Present study is aimed to evaluate the anti-microbial activity of quercetin isolated from the P. guajava leaves, against Escherichia coli (Gram negative) and Bacillus subtilis (Gram positive) which can cause foodborne infection and damage. Dried guava leaves were extracted with 70% methanol, followed by washing of the dried extract with chloroform. Quercetin was isolated by column chromatography from the ethyl acetate layer, which was obtained after partitioning of the initial extract. The efficacy of quercetin was tested by well diffusion and MIC methods where 50 μL solution per well and zone of inhibition was calculated after 72 hrs of incubation. Quercetin has shown anti-bacterial activity in both bacteria with a mean zone of inhibition of 16.5 mm and 13.75 against B. subtilis and E. coli, respectively. The claimed uses of leaves of guava in the traditional system of medicine to treat various infectious disease caused by the microbes was justified by the present study. Still, to evaluate the potential effectiveness of quercetin as a antimicrobial agent further studies are needed.