Determination of Antimicrobial and Antioxidant Activities of Extracts from Selected Medicinal Plants

In this work, attempt has been made to determine theantimicrobial and antioxidant activities of aqueous and organic extracts of Vernoniaamygdalina (1) ,Ajugaintegrifolia(2), Artemisia afra (3) , and Artemisia absinthium (4). The plant extracts were tested against clinically important bacteria- Escherichia coli,Shigella, staphylococcus aureus, and Bacillus subtilis.The results showed that methanol extract is more effective than that of aqueous extract which is in turn more effective than that of petroleum ether. The methanol extract of 3 could inhibit all test bacteria and exhibited significant (P ≤ 0.05) antimicrobial activity when compared with other herbs, with the zone of inhibition ranging from 18.33±0.58 to 26.00±1.73 mm. On the other hand, 4 demonstrated a moderate activity against the test bacteria with the zone of inhibition ranging from 5.57±0.58 to 8.00±1.67 mm. However, that of 1 and 2 had no significant antibacterial activity against test bacteria except a moderate activity against Escherichia coli with the zone of inhibition ranging from 3.09±1.47. The minimum inhibitory concentration and minimum bactericidal concentration of 3 were 0.1-2.5 and 1.2-2.5 (gm/ml) respectively against E. coli- a common enterogenic bacteria. Mechanistic insight regarding the active principle is deciphered through alkaloid free against free alkaloid. The results reinforced the fact that oxygenated metabolites are most responsible for the antimicrobials when compared with alkaloids. 1 , 2 and 3 showed significant antioxidant activity with an IC50 value of 24.2, 18.9 and 20.2 μg/mL respectively. In conclusion, 3 is relatively most effective against the test bacteria. The recorded antioxidant activities of 1 , 2 and 3 reinforce their traditional use in the treatment of liver disease.

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