Antibacterial Activities of Dichloromethane: Methanolic Leaf and Stem Bark Extracts of Psidium Guajava Linn against Selected Bacteria
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Date
2019
Authors
Ayienda, Carol Kerubo
Journal Title
Journal ISSN
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Publisher
Kenyatta University
Abstract
Antibiotics have been very effective in the management of microbial infections. However they are expensive and have many side effects. Additionally, the menace of antimicrobial resistance has resulted to the inactivity of various conventional antibiotics. Medicinal plants are used in herbal medicine to control microbial infections since they are considered cost effective and have shown less side effects. Plant extracts with medicinal value have been used to treat many diseases that can either be bacterial, fungal or parasitic among many others. Plants with medicinal value produce certain chemical elements known as phytochemicals that have antimicrobial activity. They include secondary metabolites such as flavonoids, tannins, and saponins which are the main chemical structural classes. Psidium guajava Linn is a plant which has been used in traditional medicine to manage various conditions including toothache, malaria, gastroenteritis and vomiting. This research focused determining the antibacterial activities of dichloromethane: Methanolic extracts of Psidium guajava stem bark and leaf extracts against selected microorganisms Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Salmonella typhi ATCC 19430 and Bacillus cereus clinical isolate. These microbes are normally associated with illnesses that are characterized with vomiting, enteric fevers, diarrhea and abdominal pain. The plant’s leaf and stem bark were collected from Bonchari Sub-county of Kisii County and transported to Kenyatta University. The samples were extracted using 1:1 mixture of DCM and methanol. The plant extracts antibacterial activities was established by taking measurements of the zones of inhibition in millimeters, MIC and MBC. The collected data was then analyzed using Minitab 17 statistical software, Student’s Test (T-test), one way ANOVA with P ≤ 0.05 being considered significant, followed by Tukey’s post hoc test. Both plant parts analyzed had antimicrobial activity against all the tested microorganisms. However the extracts did not exhibit any bactericidal activity (MBC) on all the tested microorganisms. The leaf extracts had MIC levels of 25mg/ml, 100mg/ml, 25mg/ml and 100mg/ml against Staphylococcus aureus, Escherichia coli, Salmonella typhi and Bacillus cereus respectively. The stem bark showed an MIC dose of 50mg/ml against all the tested bacteria. The phytochemical analysis showed the presence of all the phytochemicals tested; saponins, alkaloids, terpenoids, flavonoids, steroids and phenolic in the stem bark, while steroids were not present in the leaf extract. The results provides an enlightment concerning the antimicrobial activities of the plant extracts and their use in the treatment of several bacterial infections.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Medical Biochemistry) in the School of Pure and Applied Sciences of Kenyatta University, November, 2019