Peels of Psidium guajava fruit possess antimicrobial properties

  Background: Psidium guajava (guava) leaf extracts have been extensively studied for their anti-microbial effect. Yet, very few studies investigated the antimicrobial effect of the ripe guava fruit. Aim: This study aims at examining aqueous extracts of ripe Psidium guajava fruit, bulb, seeds and peels (harvested in autumn at Jordan River valley). Materials and methods: Decreasing concentrations of water extracts of three parts of the fruit are tested against Gram positive and Gram negative bacteria as well as the fungus Saccharomyces cerevesea using the agar diffusion method. Clinical isolates of MRSA are also included. Results: Water extracts of Guava peels at concentrations ≥ 10% are inhibitory to coagulase positive S. aureus and MRSAs, and at ≥ 1% are inhibitory to  coagulase negative Staphylococci. Water extracts of peels acted synergistically with cell wall synthesis inhibitor antibiotics towards S. aureus and MRSA strains used. HPLC-MS-MS analysis through ion trap and subsequent fragmentation of the isolated ions from peels water extracts allowed the clear identification of two well-known phenolic compounds that are known for their antimicrobial activity: Gallic acid (957.6 μg/mL) and Ferulic acid(13 μg/mL). Conclusion: The ripe fruit of Guava is a nutritionally rich fruit with an outer covering that possess antimicrobial propertie