COMAPARATIVE IN VITRO EVALUATION OF ANTIMICROBIAL AND ANTIOXIDANT ACTIVITIES ON STEMS AND LEAVES EXTRACTS OF COSMOS CAUDATUS

Currently, people are looking forward to discover the beneficial content of natural resources such as marines and herbs that might have potential in enhancing healthy living. Naturally, Cosmos caudatus is one of the promoting herbs that had been introduced long time ago by the ancient communities, furthermore in Malaysia it is traditionally been used in the treatment of few ailments such as hypertension, osteoporosis, diabetic and inflammation. Even tough, there is a previous study that has been reported on its antimicrobial and antioxidant activity in leaves of C.caudatus, however there is no proven information on comparative evaluation of the plant parts for the above said activities. Thus, an effort was made in the present study to compare and evaluate the antimicrobial and antioxidant activities of methanolic extracts obtained from different parts of C.caudatus such as stems and leaves. The selected plant parts were extracted using maceration method using methanol as solvent. Methanolic extracts of stems and leaves were tested for its antimicrobial activity against Staphylococcus aureus and Escherichia coli using Mueller Hinton Agar plate. Antimicrobial activity of stems and leaves extracts were found with minimum zone of inhibition 7.16 mm ± 0.23 and 6.78 mm ± 0.57 respectively only against S.aureus with the concentration 100 mg/ml and 200 mg/ml independently.However, both extracts showed negative results for gram negative organism. Moreover, the extract was evaluated for its free radical scavenging activity using DPPH assay. Leaves methanolic extracts of C.caudatus showed free radical scavenging activity (IC50 value) at the concentration range of 31.35-62.5 µg/ml whereas stems extract recorded 125-250 µg/ml. Nevertheless, the standard ascorbic acid showed potential antioxidant activity compared to sample extracts. To conclude the study findings, antimicrobial activity was found more susceptible against gram positive microorganism like S.aureus with stems extract compared to leaves extract and in free radical scavenging activity the leaves methanolic extract recorded more potential antioxidant properties when compared to stems extract of C.caudatus. Keywords: Cosmos caudatus, Staphylococcus aures, Escherichia coli, Mueller Hinton Agar Plate, DPPH.