Extracts from Hibiscus sabdarifa L. (roselle) have been used traditionally as a food, in herbal medicine,
in hot and cold beverages, as favouring or coloring agent in the food industry. In vitro and in vivo
studies and trials provide evidence, but roselle is poorly characterised phytochemically due to the
extraction processes. The optimization of the extraction of phenolic compounds and their antioxidant
activities is still a hot topic. In this study, the efect of solute/solvent ratio (33, 40 and 50 mg/mL),
extraction temperature (40, 50 and 60 °C) and extraction time (30, 60 and 90 min) was evaluated
through the content of phenolic compounds and antioxidant activity. A response surface methodology
through a Box–Behnken design was applied and model ft, regression equations, analysis of variance
and 3D response curve were developed. The results showed that TPC, TFC, DPPH and FRAP were
signifcantly infuenced by temperature, extraction time and solvent/solute ratio. Thus, TPC, TFC,
DPPH and FRAP varied from 5.25 to 10.58 g GAE/100 g DW; 0.28 to 0.81 g QE/100 g DW; 0.24
to 0.70 mg/mL; 2.4 to 6.55 g AAE/100 g DW respectively. The optimal experimental condition
(41.81 mg/mL; 52.35 °C and 57.77 min) showed a signifcant positive efect compared to conventional
methods. The experimental values at this extraction condition show that this optimization model is
technologically, fnancially and energetically viable as it requires a reasonable concentration, time and
temperature.

Hisbiscus, Phenolics, Extraction