Chemical composition, antioxidant and antimicrobial activities of Moroccan species of Psidium guajava extracts
[Chemical composition, antioxidant and antimicrobial activities of Moroccan species of Psidium guajava extracts]

ABSTRACT
Background. During the recent years, appropriate attention has been paid to the oxidative stress which damages the body’s cells, proteins, and DNA. Therefore, the need of antioxidants becomes a therapeutic and preventive priority. In addition, microbial infections also constitute a public health problem.
Objective. To find efficient, reliable and safe alternatives sources to synthetic antioxidants, antibiotics and antifungals drugs.
Materials and methods. Extract and essential oil of Psidium guajava were screened for their antioxidant and antimicrobial activities against gram positive bacteria (Enterococcus faecalis and Staphylococcus aureus), gram negative bacteria (Citrobacter freundii, Escherichia coli and Pseudomonas sp) and fungi (Candida albicans,Candida tropicalis and Cryptococcus neoformans), as well as to determine the functional groups of phytochemicals present in the essential oil by Fourier transform infrared spectroscopy (FTIR).
Results. The results indicate that P. guajava leaves extract demonstrated very high antioxidant activity and P.guajava essential oil showed the highest polyphenols content. The antioxidant capacity showed a significant negative linear correlation to total polyphenolic content (TPC) with Pearson’s correlation coefficients. P. guajava essential oil shows high antibacterial and antifungal activity against all the studied bacteria and fungi. The FTIR analysis of P. guajava essential oil showed the presence of several functional groups (ethers, esters, ketones, terpenes, alkanes, aldehydes, aromatic hydrocarbons, alcohols, and phenols). The relationship between the chemical composition and antimicrobial activity of P.guajava essential oil suggests that the attribution of its antimicrobial activity to a particular compound or a synergistic effects between its different constituents remains difficult.
Conclusions. The present study demonstrated that Psidium guajava is a valuable source of active compounds with antioxidant and antimicrobial activities. This finding suggests the new use of the fruits and the leaves extracts of this plant in the treatment of bacterial and fungal infections, as well as for the extraction of new antioxidants. Therefore, it is necessary to be carried out in another study to identify the active(s) compound(s) in P.guajava essential oil with respect to their mechanisms and synergistic actions.