Parametric Study on the Extraction of Flavonoids and Phenolics From Waste Onion Leaves by Conventional Solvent Extraction and Microwave Assisted Extraction Using Aqueous Acetone as Solvent

Author : Bonayon, Maria Teresa Garalde
Major Adviser : Capunitan, Jewel A. 
Committee Members : Borines, Myra G.; Dizon, Lisa Stephanie H.; Demafelis, Rex B.
Year : 2019
Month : June
Type : Thesis
Degree: BS
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Quercetin, the major flavonoid in onion peels and skins, had been reported to exhibit strong anti-oxidant activity and potential anti-inflammatory, anti-cancer effects. Its added health value has made it the target of recent researches. In this parametric study, the effects of temperature (40 °C, 60 °C), aqueous acetone concentration (40 %v/v, 80 %v/v), and extraction time (1 hours, 4 hours) were investigated for conventional solvent extraction (CSE). Microwave-assisted extraction (MAE) was also performed using power level (10 %, 30 %), acetone concentration (40 %v/v, 80 %v/v) and irradiation time (10 seconds, 30 seconds) as parameters. The extracts were tested for total flavonoid content (TFC) using aluminum chloride colorimetry with quercetin as standard (mg QE/g dw) whereas total phenolic content (TPC) was measured using the Folin-Ciocalteu method with gallic acid as standard (mg GAE/g dw). The maximum flavonoid and phenolic content extracted is 7.53 mg QE/g dw and 12.54 mg GAE/g dw, respectively, from shaking using 80 %v/v acetone for 18 hours. The TFC content of CSE extracts increased logarithmically with increasing acetone concentration and decreasing temperature. TFC decrease more significantly with increasing temperature and increased acetone concentration. Only temperature was found to significantly affect TPC of CSE and the effect was negative. Both TFC and TPC of MAE extracts increased at higher acetone concentrations and lower irradiation time. TFC has a more significant increase at lower irradiation times while TPC increased at higher irradiation time and increased acetone concentration. MAE and CSE showed no significant effect on the recovery and cost of extraction of phenolic and flavonoids.

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