Production Optimization of Roselle (Hibiscus Sabdariffa L.) Calyces Aqueous Extract

Roselle (Hibiscus sabdariffa Linn.) is not only a medicinal plant described in European Pharmacopoeia, but also useful herb in east medicine. Polyphenols present in roselle are responsible for high antioxidant activity that provides pharmacological effect. Polyphenols are known to induce avoidance of oxidative stress. Anthocyanins – is one of the flavonoid groups that are responsible for intensively red color of roselle extracts. The aim of this work: selection of optimal aqueous extraction conditions of roselle calyx. Tasks: application of different extraction of roselle calyx conditions; quality evaluation of obtained aqueous extracts by determining total amounts of polyphenols, flavonoids, radical scavenging activity; coloring power evaluation of obtained extracts. Several classical and modern extraction methods were used for extraction: constant stirring on magnetic stirrer, ultrasonic, microwave assisted and pressurized hot water extractions. Obtained extracts were evaluated spectrophotometrically by determining coloring power, total amount of polyphenols, flavonoids and radical scavengind activity. Total amount of phenolic compounds was determined by Folin-Ciocalteu method. Total amount of flavonoids was determined by colorimetric method in the presence of aluminum chloride. Radical scavenging activity was determined with the aid of free DPPH• radical. Coloring power was determined by method described in European Pharmacopoeia. Largest amount of phenolic compounds (3.12 mgGAE/ml ± 1.8%) and flavonoids (0.877 mgRE/ml ± 3.73%) was determined in extracts prepared by pressurized hot water extraction. Highest radical scavenging activity (0.198 mgAAE/ml ± 7.41%) was observed in extracts prepared in magnetic stirrer where 80°C temperature was kept during the whole extraction time of 30 min. Highest amount of pigments was extracted by pressurized hot water extraction. Pressurized hot water extraction should be implemented whenever high yields of polyphenols and flavonoids are priority of extraction process. Magnetic stirrer should be used whenever higher radical scavenging activity is needed in prepared extracts