Extracting Quercetin from Different Plant Sources, Purifying It Using Different Extraction Methods (Chemical, Physical, and Enzymatic), and Measuring Its Antioxidant Activity

Background: Flavonoids are among the most important compounds found in plants, since laboratory studies have shown them to be a daily requirement in human diets due to their various health benefits. Therefore, this study focused on extracting, purifying, and measuring the antioxidant activity of the flavonoid quercetin, which is widely found in plants and possesses a variety of biological activities, from different plant sources. Methods: The extraction of quercetin was performed using several methods (chemical, physical, and enzymatic) and several extraction solutions (water, ethanol, and chloroform) from several plants (spinach, dill, Onion Skin, Pistacia eurycarpa, sumac, digalkhasab chemri, and leelwi chemri). The alcoholic extract extracted by chemical method was purified and the content of total flavonoids based on quercetin in all plant extracts was determined using adsorption chromatography on a silica gel column (100–200 mesh), followed by thin layer chromatography (TLC). TLC and high performance liquid chromatography (HPLC) were used to assess the purity of quercetin. The ability of quercetin to capture free radicals using 2,2-diphenyl-1-picrylhydrazyl (DPPH) was compared to that of butylated hydroxytoluene (BHT). Statistical analyses were performed using completely randomized designs (CRD) for factorial experiments, and the least significant difference (LSD) test was used to calculate the significant differences between the averages of the coefficients at the 0.05 probability level. Results: The alcoholic Pistacia extract extracted by chemical method yielded the highest concentration of quercetin (84.037 mg/g). Furthermore, it was found that quercetin purified from Pistacia possessed strong antioxidant activity, and its antioxidant activity increased with increased concentration. Conclusions: Pistacia eurycarpa showed the highest quercetin content among the assessed plants. Moreover, solvents played a major role in extracting plant components due to the high polarity of flavonoids. Quercetin purified using a silica gel column demonstrated antioxidant activity.