Phenolics are bioactive compounds already reported in Hibiscus sabdariffa (roselle). The present study reports the development and validation of the analytical microwave-assisted extraction (MAE) method for the determination of phenolic compounds in roselle flowers to establish their positive contribution to human health. Prior to the optimization, a study for identifying phenolic compounds revealed that chlorogenic acid, protocatechuic acid, caffeic acid, and rutin were presented in Roselle. Three factors affecting MAE, viz. temperature, solvent composition, and sample to solvent ratio, were optimized employing a Box-Behnken Design (BBD) in conjunction with response surface methodology (RSM). The maximum extraction recovery was achieved using the extraction temperature of 68 °C, solvent composition of 59% MeOH in water, and 20:1 solvent to sample ratio. The kinetics experiment confirmed full recoveries (92–119%) at 15 min. Subsequently, method validation showed a satisfactory result, including low detection limits from 0.219 mg L−1 (caffeic acid) to 0.374 mg L−1 (chlorogenic acid). Both precisions and accuracy met the acceptances by AOAC. Finally, the method was successfully applied to quantify phenolics in the two most common varieties of Roselle. Chlorogenic acid was found as the main phenolic compound in both varieties
Comparison of microwave assisted extraction (MAE) with variations of power and infusion extraction method on antibacterial activity of rosella calyx extract (Hibiscus sabdariffa)
