Optimization of Quercetin Extraction from Green Tea (Camellia sinensis) Using Central Composite Design, and the Pharmacological Activity of the Extract

Quercetin is one of the six subclasses of flavonoid compounds1, which has antioxidant properties2. Quercetin is found in many common foods including green tea1, apples, onions and berries3. Its structure with the indicated C atoms and rings is presented in Figure 1. Because of its interesting chemical and biological properties, quercetin has been one of the most studied flavonoids. Quercetin is a major bioflavonoid in the human diet4. Reactivity of phenolic compounds with free radical species and formation of considerably less reactive phenoxy radicals indicates the antioxidant activity of quercetin5. The different methods of quercetin extraction, such as ultrasonic6,7, microwave-assisted8, solid-liquid extraction at ambient temperature9, and elevated pressure10 supercritical extraction with carbon dioxide11 from Bobgunnia madagascariensis, Caesalpiniaceae12, Coriundrum sativum L.13, Abutilon indicum14, Butea frondosa15, Petasites japonicus16, Euonymus alatus (Thunb.) Sieb.17, Citrus bergamia18 were described in the literature. Solvents, such as chloroform12, methanol, ethanol14 and acetone or mixtures of these and water are used for extraction19. For identification of the extracted quercetin, preparative TLC12, RP-HPLC11,13,14,20–22, micellar liquid chromatography23 and GC-MS24 were used. A traditional approach, well known as the “One Variable At a Time” (OVAT), is commonly applied for investigation of the effects of extraction paramOptimization of Quercetin Extraction from Green Tea (Camellia sinensis) Using Central Composite Design, and the Pharmacological Activity of the Extract