Antioxidant and antimicrobial activities of three different solvent extracts of guava leaf (Psidium guajava L.)

Abstract

Guava is a tropical plant found in hot climate areas in South America, Europe, Africa and Asia. Previous research has shown that the phenolic compounds found in guava leaves possess antioxidant and antimicrobial properties. The aim of this study was two‐fold: 1) to determine the antioxidant capacity of guava leaf water, ethanol, and methanol extracts by measuring their total phenol and flavonoid content, and 2) to evaluate the antimicrobial capacity of guava leaf extracts against four different microbes (S. aureus, E. coli, T. mentagrophytes, and T. rubrum). Phenolic content was the highest in the guava leaf water extract, and the flavonoid content in the guava leaf water and ethanol extracts were higher than in the methanol extract. Radical scavenging property, as denoted by 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH•) and 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) levels, was higher in the guava leaf water extracts. Nitric oxide scavenging capacity was not significantly different among the guava leaf extracts. Ethanol, methanol, and water guava leaf extracts significantly inhibited microbial growth, with the ethanol guava leaf extract showing the highest activity against the S. aureus and E. coli. This suggests a relationship between the phenolic content and the antioxidant activity, as well as between the flavonoid content and antimicrobial activity of guava leaf extracts.