Antioxidant Activity of Acid Hydrolyzed Fraction and Ethanol Extract of <i>Musa balbisiana</i> BBB and <i>Hylocereus polyrhizus</i>

Background: Plants contain secondary metabolites, including flavonoids, which are bound to glycosides or not in the form of free molecules. The hydrolysis treatment in this study was expected to increase antioxidant activity by converting bound forms into free molecules. Methods: To evaluate the antioxidant activity, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging test was used. The obtained half-maximal inhibitory concentration (IC50) value indicates antioxidant activity. This study aimed to determine the effect of acid hydrolysis treatment on the hexane-insoluble fraction of Kepok banana heart (Musa balbisiana BBB) and water fraction of red dragon fruit skin (Hylocereus polyrhizus) on increasing DPPH radical scavenging activity. Acid hydrolysis was carried out by adding 2 N HCl and then measuring antioxidant activity through the DPPH radical scavenging test using a UV-Vis spectrophotometer. To determine the compounds in the hexane and water-insoluble fractions that act as antioxidants, qualitative analysis was used and total phenolic and flavonoid contents were determined. Results: The hexane-insoluble fraction of Kepok banana heart hydrolyzed for 3 hours (IC50 25.00 µg/mL, total phenolics 38.40 µg/mL, and total flavonoids 15.90 µg/mL) and the water fraction of red dragon fruit peel hydrolyzed for 1 hour (IC50 7.74 µg/mL, total phenolics 62.50 µg/mL, and total flavonoids 29.70 µg/mL) showed the highest antioxidant activity. Conclusion: The highest antioxidant activity of Kepok banana heart was observed in the hexane-insoluble fraction hydrolyzed for 3 hours, while the highest antioxidant activity of the red dragon fruit was observed in the water fraction hydrolyzed for 1 hour. Therefore, acid hydrolysis of the hexane-insoluble fraction of Kepok banana heart for 3 hours and hydrolysis of water fraction of red dragon fruit skin for 1 hour could increase antioxidant activity.