Optimization of quercetin extraction from onion leaves (Allium cepa L.)

Allium cepa L. was known as one of the most important vegetables worldwide that posseses many nutritional value as well as medicinal properties. Onion leaves comes from the .family of Alliaceae under the class of monocotyledons. Based on previous studies, it shown that onion could be used for medicinal purpose due to several properties that available such as antioxidative, anticarcinogenic and enzymes-inhibiting activities. This research, study the most optimize conditions for extracting the quercetin compounds from onion leaves using experimental designed and High-Performance Liquid Chromatography (HPLC) analysis method. Four parameters such as extraction method, polarity of solvent, extraction temperature and time of extraction was tested in the study. Using standard quercetin sample, the result from HPLC were compared to find which parameters were most optimized. The concentration of quercetin from various extracts was calculated using standard curve equation which is y= 21441(x) — 14629, r²= 0.999. Most optimum condition in extracting quercetin from onion leaves was found out by using conventional water bath extraction method with methanol as the solvent at 55 °C for 30 minutes. Amount of quercetin extracted using conventional water bath was (19.80 ± 1.57 pg/mI) while another method,Microwave Extraction Method (MAE) was (18.97 ± 2.05 pg/m1) . The amount of quercetin from convetional water bath was higher due to the degradation of quercetin in MAE at 280 W. These parameters were chosen as the optimum parameters due to the highest amount of quercetin yield. Quercetin has a lots of nutritional values and medicinal usage that can be exploited. There could also be others optimum condition that will yield higher amount of quercetin.