PHYTOCHEMICAL SCREENING AND ANTIMICROBIAL ACTIVITIES OF RADISH (Raphanus sativus L.) TUBERS AND SEED CRUDE EXTRACTS AGAINST SELECTED HUMAN PATHOGENS

Abstract

Traditional plants have been used for centuries to treat different human ailments. The phytochemical constituents of these plants contributed much to the reported antimicrobial activities. This study was carried out to determine the phytochemical composition of the crude extracts of the tuber and seeds of Raphanus sativus and evaluate their antimicrobial activities against Eschericia coli O157:H7, Staphylococcus aureus,Candida albicans and Aspergillus niger. Qualitative analysis of the major secondary metabolites was conducted following standard phytochemical screening procedures. The antimicrobial activities of the crude extracts were also evaluated against test organisms using the disc diffusion method at concentrations of 100, 125, and 150 mg/mL. The MIC, MBC, and the MFC of the crude extracts were assessed using the broth dilution method. The results indicated that the crude extracts of the tuber and seeds of Raphanus sativus demonstrated bioactive compounds such as tannins, saponins, steroids, terpenoids, and alkaloids. However, phlobatannins were absent in both plant parts. On the other hand, flavonoids were absent only from the aqueous and ethanol seed extracts. The ethanol extracts of the seeds at the concentration of 150 mg/m1 showed a significantly high zone of inhibition (15.16±0.28 mm) against S. aureus (P < 0.05). Among the test organisms, E. coli exhibited a significantly (P < 0.05) low inhibition zone (10.7±0.17mm) when tested using water extracts of the tuber (150 mg/ml). The ethanol extracts of the seeds (150 mg/ml) revealed the maximum antifungal activity (12.47±0.11mm) against A. niger. The tuber and seed crude extracts showed a statically significant inhibitory effects at p<0.05. The MIC (12.5 mg/ml) of the ethanol extracts of the tuber and seeds revealed its MBC at 25 mg/ml concentration against S. aureus. The ethanol extracts of tuber demonstrated the strongest antifungal activity with MIC of 20.83±7.21 mg/mL and MFC of 41.67±14.43 mg/mL against A. niger. On the basis of these results, it can be concluded that the parts of Raphanus sativus and the extraction solvents used have effects on the antimicrobial activities of the crude extracts. Thus, this suggests that Raphanus sativus tuber and seeds have the potential to be used as a source of alternative antimicrobial agents.