SYNERGISTIC ANTIBACTERIAL AND ANTIOXIDANT EFFECTS OF ALTERNANTHERA SISSOO AND COSMOS CAUDATUS METHANOL EXTRACTS

Abstract

Antibacterial and antioxidant properties are important in medical applications, nutrition and food preservation. A combination of these properties plays a significant role in promoting health, preventing disease, and maintaining overall well-being. As current drugs have become less effective and have come with bad side effects, this has increased the need for safer alternatives like plant-based remedies that are more effective. Thus, this study aims to evaluate the antibacterial and antioxidant activities of a crude methanolic extract from a mixture of Alternanthera sissoo (Brazilian spinach) and Cosmos caudatus (Ulam raja). The concentrations of methanolic crude extract used were 500 mg/mL, 250 mg/mL, 125 mg/mL and 62.5 mg/mL. Antibacterial activity was first tested using the disk diffusion method. However, minimal and no visible inhibition zones were observed at most of the evaluated concentrations used. Therefore, a Minimum Inhibitory Concentration assay using a 96-well plate was applied. The results showed that wells with concentrations between 500 mg/mL down to 7.81 mg/mL were clear, indicating complete inhibition of bacterial growth. Slight turbidity was observed at 3.91 mg/mL and 1.95 mg/mL, particularly in wells with Bacillus cereus, suggesting low effectiveness at lower concentrations. For antioxidant evaluation, the DPPH radical scavenging assay was conducted. The results demonstrated that antioxidant activity increased with higher extract concentrations. The highest concentration (500 mg/mL) recorded the lowest absorbance value at 517 nm (0.125), corresponding to the highest scavenging activity of 78.55%. As the concentration decreased, a gradual decline in antioxidant activity was observed, with the lowest still maintaining a strong activity at 68.81%. In conclusion, the methanolic extract of Alternanthera sissoo and Cosmos caudatus mixture has been proven to possess both antibacterial and antioxidant properties, highlighting its potential for future development.