Antioxidant and Antimicrobial Activity of Psidium guajava (Pomifera and Pyrifera) Aqueous Leaf Extract Varieties’
Grace Gakii Keddy
Department of Chemistry, Catholic University of Eastern Africa, P.O. Box 62157-00200, Nairobi, Kenya.
Patrick Gachoki Kareru
Chemistry Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya.
Sammy Indire Wanakai *
Chemistry Department, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya.
Mercy Wanjuki Karenju
Department of Chemistry, Catholic University of Eastern Africa, P.O. Box 62157-00200, Nairobi, Kenya.
George Kiprono Kisoi
Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62,000-00200, Nairobi, Kenya.
Peter Lemei Njenga
Department of Chemistry, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Aims: Psidium guajava (Pomifera (red) and Pyrifera (white)) is commonly used in traditional medicine to treat gastrointestinal disorders. In this study, the antioxidant and antimicrobial activity of methanol extracts of P. guajava (Pomifera (Red) and Pyrifera (White) leave varieties were investigated.
Methodology: The total phenolic (TPC) and flavonoid (TFC) contents and antioxidant capacities in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, were determined, and the correlations among the results were assessed. The antimicrobial activity was assessed through agar disc diffusion assays.
Results: Phytochemical screening showed that the extracts had alkaloids, glycosides, saponins, triterpenoids, phenols, and flavonoids in different abundances. The aerial part- (Pomifera (red) and Pyrifera (white)) extract contained 106.502.97 and 122.072.73 mg/g in QAE phenolic content, 2650.6527.48 and 2486.829.10 mg/g in RE of flavonoids, 17.860.19 and 10.160.07 mg/g in TAE of Tannins, 69.500.14 and 10.500.01 alkaloid content, and 7.25.500.11 and 17.750.09 saponin content and displayed significant antioxidant capacity in the DPPH (IC50 = 52.17 ± 7.30 μg/mL) assay. By contrast, the P. guajava Pyrifera (white) extract contained high amounts of TPC (87.72 ± 7.75 mg GAE/g) and TFC (25.60 ± 1.57 mg QE/g). The leaf extract showed the highest inhibitory activity against highest activity was observed against E. Coli, S.E, and S. aureus (14, 15, and 16) respectively. GC-MS revealed presence of Sesquiterpenes, terpenes, and triterpenes. The leaves also contain vitamins of measurable amounts. Generally, the extracts evaluated showed potent antifungal activity against selected bacterial strains.
Conclusion: The results showed that P. guajava (Pomifera (red) and Pyrifera (white)) possesses different phytochemicals displaying significant antioxidant and antimicrobial activities, thus lending credence to its use in traditional medicine.
Keywords: GC-MS, Psidium guajava, total phenols, antioxidant activity, Staphylococcus aureus, antimicrobial activity