Microwave-Assisted Extraction and Solid-Phase Separation of Quercetin from Solid Onion ( Allium cepa L.)

The challenge of extraction of natural product in the twenty-first century is to achieve 100% selectivity of the desired product and develop renewable energy based processes. An object of the present work is to provide a method for producing specific bioactive compounds from agricultural products. A simple protocol was used to obtain the conditions of microwave-assisted extraction (MWAE) and ultrasound-assisted extraction (USAE). Total quercetin content under microwave irradiation for 150 sec at pH 6.25 (209 mg/ 100 gm F. wt). The effects of operating conditions, such as extraction time and pH on the extraction yield of quercetin were studied. Microwave-assisted ionic liquid-based silica sorbent (ILSis) was developed by a process involving surface chemical modification of commercial silica using a synthesized ionic liquid and characterized by FTIR. The obtained particles were successfully used as a special sorbent in a solid-phase separation process to isolate quercetin and its glycosides from solid onion. Different washing and elution solvents, such as water, water/methanol (v/v), and pure methanol were evaluated. Ionic liquid-based silica sorbent was compared with traditional C18 sorbent and it exhibited higher selectivity. The target compounds in solid onion containing quercetin and its glycosides were determined.