Novel Strategy for Optimizing the Antibacterial Activity of Psidium guajava Against Clinical Isolates of Escherichia coli, Staphylococcus aureus, Salmonella spp., and Streptococcus spp.

The development of a new antibiotic is a challenging task, with an estimated failure rate of 95%. Minor changes in the chemical structure of a drug, such as stereochemistry, geometry, or functional group modifications, can significantly impact its medicinal activity. In this study, we aim to devise novel strategies for optimizing the antimicrobial properties of guava leaf extract through simple reactions, either by self-reaction or combination reactions with a reagent, drug, or different plant extract. Fourier transform infrared spectroscopy analysis revealed conjugation and formation of new functional groups in the prepared sample of Guava Guava (GG) and Guava Aspirin Guava (GAG), which were further confirmed by weight analysis. The results demonstrated that the antimicrobial activity of medicinal plants can be improved or optimized through simple reactions, such as combining the plant extract with a non-antimicrobial drug like aspirins or adding a small volume of concentrated sulfuric acid to the plant extract by heating at a temperature range of 100 – 110°C. Among the two combinatory methods used, GG exhibited better performance in inhibiting the growth of all tested bacterial strains at a concentration of 0.1 mg/mL compared to GAG at the same concentration, which inhibited the growth of only two bacterial strains: Escherichia coli and Streptococcus spp. These methods can be further explored and applied in various studies, including antifungal, anti-inflammatory, antiviral, and anticancer research, leveraging the availability and diverse range of natural products found in medicinal plants.