Optimization of stirring-assisted extraction of anthocyanins from purple roselle (Hibiscus sabdariffa L.) calyces as pharmaceutical and food colorants

There is a tremendously high demand for multifunctional colorants in the food and pharmaceutical industries. Anthocyanins in roselle (Hibiscus sabdariffa L.) are plant pigments with dual purposes: Natural dye and pharmacologically active ingredient. Therefore, a suitable extraction technology applicable on an industrial scale is needed. This research sought to optimize the stirring-assisted extraction (SAE) conditions (solvent type, extraction time, and the ratio of crude drug weight to volume of solvent) for high anthocyanin contents. Extracts were evaluated by color, pH, total anthocyanin content, and free-radical scavenging activity using DPPH. Results showed that SAE is more effective than simple maceration and ultrasound-assisted extraction. Optimal SAE conditions for anthocyanin extraction from roselle calyces are 50% ethanol solvent acidified with 2% citric acid, 15-min extraction, and a crude drug-solvent ratio of 1:15 g/mL. When met, a dark red extract was produced with a pH of 2.78, total anthocyanin content (cyanidin-3-glucoside equivalent) of 4.03 mg/g crude drug, and IC50 equal to 244 ppm of the crude drug. The optimal conditions found in this study are suitable for extraction on a laboratory scale without sophisticated instrumentation, which can be scaled up for the mass production of natural colorants in the food and pharmaceutical industries