Phytochemical analysis and antimicrobial activity of Carica papaya l. Var. Wainamalo extracts against selected microorganisms in Maseno, Kenya.

Abstract

ABSTRACT Carica papaya L. Variety Wainamalo has been used by the Luo community in Lake Victoria region as medicine for a long time and this constitute the reason for choice of this plant for this study. The number of emerging multi-drug resistant microbial strains is continuously increasing and has become a serious threat to successful treatment of infectious and opportunistic diseases of Human Immunodeficiency Virus-Acquired Immune Deficiency Syndrome (HIV-AIDS) victims. Plant derived antimicrobials have received considerable attention in recent years. It affects not only the economy, but the general well-being of people with more serious impacts in developing countries. Many plants have been used because of their antimicrobial traits such as compounds synthesized in the secondary metabolism. Little is known about the phytochemical and antimicrobial activities of C. papaya Variety Wainamalo extracts on pathogenic microorganisms such as Escherichia coli, Staphylococcus aureus and Candida albicans, which are known to cause many opportunistic infections among Human Immunodeficiency Virus-Acquired Immune Deficiency Syndrome(HIV-AIDS) infected patients in Lake Victoria region. This study was set to determine the phytochemical and antimicrobial activity of extracts of Carica papaya L. Var. Wainamalo and to determine the minimum inhibitory concentration of seed, leaf and bark extracts on Escherichia coli, Staphylococcus aureus and Candida albicans. Carica papaya plant materials were collected from a farm in Kiboswa, Kisumu County and were taken to Maseno university botany laboratory for processing. Fruits, bark and leaf materials were washed with tap water, rinsed in sterile distilled water, and dried under room temperature for 30 days. Fruits were cut open to extract the seeds. The materials were then cut into small pieces and ground into powder separately. One hundred grams powder was transferred into five hundred millimeter of water, 95% ethanol and 95% acetone in conical flasks. The powder was added, stirred and mixture was allowed to stand for 24 hours. Then the mixture was filtered through a Whatman filter paper No 1 after decantation. Phytochemical compounds of the leaf, seed and bark were then extracted using soxhlet apparatus using water, 95% ethanol and 95% acetone respectively. The filtrates were concentrated with a rotary evaporator at 450C. The three test organisms were subjected to five C. papaya extract concentrations of 0% (control), 25%, 50%, 75% and 100% using disc diffusion method and Mueller Hinton agar replicated three times. Plant extracts were isolated and MIC was determined by serial dilution. Zone of inhibitions were measured in millimeters. Analysis of variance was carried out using SAS package. Treatment means were separated and compared using Tukey LSD at significance level P. The study revealed the presence of alkaloids, flavonoids, tannins, phenols, saponins, glycosides, anthoscyanins and tepernoids. Athraquinones were found to be absent in seed and bark extracts. There were significant differences among plant parts extracts, solvents used and microorganisms tested. The acetone extracts of the seed, leaf and bark did not show any activity against C. albicans. Ethanol bark and seed extracts demonstrated higher activities against the test microbes with the highest activity (9.82 and 8.87 mm) against S. aureus. Ethanol leaf extract had higher inhibition of 8.13mm in E. coli. Higher ethanol extracts inhibitions may be attributed to more active components present as a result of high polar solubility properties of ethanol. Minimum Inhibitory Concentration for E. coli and S. aureus was 0.025mg/ml while for C. albicans was 0.05mg/ml. The antimicrobial activity of the extracts on the tested microorganisms may be due to growth inhibition resulting from alteration of the cell biochemical activities and disruption of cell wall integrity. Differences in minimum inhibitory concentration may be due to variable sensitivity of the microbes to the phytochemical substances in C. papaya extracts. The results provide evidence that C. papaya L. Var. Wainamalo may serve as a potential source of new antimicrobial agents in the treatment of infections caused by the three test organisms. Purification of bioactive compounds can, thus, be further studied for the development of novel antimicrobial therapies.