PHYTOCHEMICAL SCREENING FOR ANTIMICROBIAL ACTIVITIES OF THE EXTRACTS OF GUAVA (Psidium guajava L.) AGAINST ENTERIC BACTERIAL PATHOGENS

Abstract

Phytochemicals are important as protective and disease fighting compounds. The guava (Psidium guajava L.) is a phytotherapic plant used in folk medicine. It is believed to have active components that help to treat and manage various infectious diseases. The present study was carried out to screen and quantify the major phytochemicals and to evaluate antibacterial activities of guava leaf and bark extracts. Extraction was done by maceration using ethanol solvent. Qualitative analysis of phytochemicals was carried out using standard protocol and phytochemical contents of leaf and bark extracts or powders were determined using spectrophotometric and gravimetric methods. Antibacterial activities of guava leaf and bark extracts were determined by disc diffusion and broth dilution methods. The results of phytochemical analysis revealed the presence of alkaloids, saponins, steroids, tannins and terpenoids and the absence of flavonoids and phlobatannins in both leaf and bark extracts. The concentration of crude alkaloid (121 mg/g), terpenoid (110 mg/g), phenolic (3.92 mg /g) and tannin (3.05 mg/g) constituents were higher in leaf extract than bark extract while that of saponin (82 mg/g) was higher in bark extract than in leaf extract. The results of antibacterial activities revealed that both leaf and bark extracts have inhibitory activities against both gram-positive and gram-negative isolates. Both leaf and bark extracts resulted in the same high mean zone of inhibition (10 mm) against Salmonella Typhi. Staphylococcus aureus was inhibited at the highest value of minimum inhibitory concentration (7.5 mg/g, 5 mg/g) by leaf and bark extracts, respectively. On the basis of the present finding, guava leaf and bark extracts might be good candidates in the search for a natural antimicrobial agent. This study provides scientific understanding for further isolation and identification of the specific active compound of the guava leaf and bark extracts that responsible for the antibacterial activity