Joraen S. Talamor (March 2014)
Philippine Science High School Western Visayas Campus – Department of Science and Technology (DOST-PSHS WVC), Brgy. Bito-on, Jaro, Iloilo City 5000, Philippines
ABSTRACT
Psidium guajava is an evergreen shrub or small tree that is part of the Myrtaceae family. Guava leaves contain antioxidants, antibacterial agents, anti-inflammatory agents, and beneficial tannins. The parts of the guava plant are potential ingredients for the formulation of soap but, presently, people care more about making their skin look white, resulting to regular use of whitening soaps. The more frequently used and more affordable types of whitening soaps are the ones containing the agent Kojic acid, a chemical produced by Aspergillus oryzae, a common species of fungi. Kojic aicd is a chemical which blocks an enzyme called tyrosinase, which reacts with tyrosine and produces melanin, resulting to skin darkening. Apart from being a whitening agent, Kojic acid also contains antifungal and antibacterial properties. According to Aytemir (2003b, 2004), Kojic acid and guava soap both have antibacterial properties without imposing any conflict to each other. The antibacterial property of this mixture with varying concentrations of 57%, 67%, and 80% of Psidium guajava leaf extracts were tested against Staphylococcus aureus bacterial culture through disk diffusion. The plates of bacterial culture containing the antibacterial disks were isolated at room temperature and the zones of inhibition of the S.aureus culture against the disks were measured after one and a half days. All the plates showed activity against the test organism. The results of the study suggest that the concentration of 67% of Psidium guajava leaf extracts added to Kojic soap is the mixture that best inhibits the growth of Staphylococcus aureus.