Comparative Study of the Antioxidant and Antimicrobial Activities of Compounds Isolated from Solvent Extracts of the Roots of iSecurinega virosa/i

摘要

There are several lines of indications on the importance of plants as accepted sources of therapeutic agents since most synthetic antioxidants and antibiotics have been associated with cytotoxicity and/or microbial resistance. In this study, the antioxidant and antimicrobial activities of a brown compound recovered from the ethanol extractable fraction (EEF) and white crystals isolated from the chloroform-methanol elution (CME) following column chromatography of the ethanolic extracts of roots of Securinega virosa were examined. Preparations from the white crystalline compound recorded greater antioxidant activity and antimicrobial activities than the crude ethanol extracts of S. virosa. Both the ethanol extract and the crystals showed significant antimicrobial activities against all microbes employed in this study. The crystalline compound demonstrated the highest zone of inhibition against the microbes Enterococcus faecalis with varied inhibitory activities with respect to other microorganisms. The least inhibition was against Pseudomonas fluorescens. The overall range was 8.0 - 22.5 mm. The EEF of the roots of S. virosa recorded its highest activity against Staphylococcus aureus and Escherichia coli. There was varied inhibitory activity against other organisms;the least was against Micrococcus liteus. The zone of inhibition ranged 6.33 - 17.67 mm. Similar to the trends in susceptibility test, the EEF showed appreciable minimum inhibitory concentration (MIC), ranging from 3.13 - 25 mg/mL against test microorganisms while the crystalline preparation had a MIC range of 1.5 - 25 mg/mL except against Salmonella typhii which was 50 mg/mL. Both extracts demonstrated their highest activity against E. faecalis reducing significantly in a dose-dependent manner by each sample against the rest of the test microbes. However, the standard broad-spectrum antibiotic, chloramphenicol, used elicited a zone of inhibition ranging from 0 - 30 mm but with no activity against Streptococcus thermophilus. We conclude that both the EEF and the white crystal compound isolated from the CME chromatographic fraction are potentially excellent sources of antioxidant and antimicrobial compounds.