Extraction procedure optimization of roselle (Hibiscus Sabdariffa L.) calyces

Abstract

Roselle (Hibiscus Sabdariffa L.) calyces is a medicinal herbal material described in European Pharmacopoeia also known in Eastern medicine for its antihypertensive, antiinflammatory, diuretic, atherosclerosis reducing and cancer preventive effects. Pharmacological effects are addressed to polyphenolic compounds present in roselle. Aqueous extract color is intensively red; intensity represents the extent of extracted anthocyanins, mainly, cyanidin and delphinidin. The aim of this work was optimization of aqueous extraction procedure of roselle calyces. Classical and modern extraction methods were applied in order to prepare roselle extracts. Magnetic stirrer, ultrasound, microwave assisted and pressurized hot water extraction modes were used. The quality of prepared extracts was evaluated spectrophotometrically by determining coloring power, total phenolic compounds and total flavonoid content and evaluating radical scavenging activity. Total phenolic compound content was determined by Folin-Ciocalteu method. Total flavonoid content was determined by colorimetric method in the presence of aluminum chloride. Radical scavenging activity was evaluated using free DPPH• radical. Coloring power was determined by method, described in European Pharmacopoeia. Highest recovery of pigments was obtained by pressurized hot water extraction. This method also provided highest recovery of phenolic compounds (3.12 mg GAE/ml ± 1.8%) and flavonoids (0.877 mg RE/ml ± 3.73%). Highest radical scavenging activity was observed in extracts prepared with the aid of magnetic stirrer for 30 min. at 80°C temperature (0.198 mg AAE/ml ± 7.41%).