Sidaguri (Sida rhombifolia) is widely distributed in tropical and subtropical regions and has been reported to possess many bioactive compounds that are beneficial for human health, including polyphenolics having antioxidant activities. The objective of this study was (1) to optimize ultrasound-assisted extraction (UAE) of Sidaguri and (2) to evaluate antioxidant activities of extracts resulting from the optimized condition using radical scavenging assay of 2,2′-diphenil-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid. The optimum UAE conditions obtained were solvent to solid ratio of 26:1, temperature of extraction of 45.45°C, methanol concentration of 42%, power of sonication of 86%, and time of extraction of 5 minutes. Sidaguri obtained from locations of Kretek and Ngemplak had the highest radical scavenging activity accounting for 83.69% ± 0.30% and 82.95% ± 0.49%, respectively.
Key words: Sidaguri, principal component analysis, ultrasound-assisted extraction, antioxidant activities, partial least square.
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