Response surface-based optimization of antioxidant-rich extracts from Orthosiphon aristatus (Blume) Miq. via microwave-assisted extraction

This study aimed to optimize the extraction of total phenolic content (TPC) and antioxidant capacity from Orthosiphon aristatus (Blume) Miq. leaves using microwave-assisted extraction (MAE) and Response Surface Methodology (RSM) with a Box-Behnken Design. The optimization considered three independent variables: extraction time, ethanol concentration, and solid-liquid ratio. Antioxidant activity was evaluated using four different assays: DPPH, ABTS, FRAP, and CUPRAC. The optimal extraction conditions—3.465 minutes extraction time, 60% ethanol concentration, and a 1:20 solid–liquid ratio—produced high levels of TPC and antioxidant activities. The optimization model exhibited strong predictive accuracy, yielding a desirability score of 0.81 and minimal deviation between predicted and experimental values. These findings confirm that MAE, in combination with RSM, provides a robust and efficient approach for extracting bioactive compounds from O. aristatus, establishing a solid foundation for scaling up applications in the pharmaceutical, nutraceutical, and functional food industries.