Parametric Study on the Extraction of Flavonoids and Phenolics from Waste Onion Leaves by Conventional Solvent Extraction and Microwave Assisted Extraction Using Aquous Ethanol as Solvent

Author : Mangilet, Audrey Dianne Generoso
Major Adviser : Capunitan, Jewel A.
Committee Members : Dizon, Lisa Stephanie H.; Borines, Myra G.; Demafelis, Rex B.
Year : 2019
Month : June
Type : Thesis
Degree: BS
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This study focused on the extraction of flavonoids and phenolics from waste onion leaves by conventional solvent extraction (CSE) and microwave-assisted extraction (MAE) using aqueous ethanol as solvent. The effects of three factors: ethanol concentration (A), temperature (B for CSE)/ power level (B for MAE), and extraction time (C), on the responses, total flavonoid content (TFC) and total phenolic content (TPC), were evaluated. For CSE, ethanol concentration (A), extraction time (C), and the AB, AC, AB, and ABC interactions were significant on TFC; while ethanol concentration (A), temperature (B), extraction time (C), and the AB and AC interactions were significant on TPC. For MAE, ethanol concentration (A) and power level (B) were significant on TFC; while only ethanol concentration (A) was significant on TPC. From the maximum extractable flavonoid and phenolic content, 8.61 mg QE/g DW and 8.95 mg GAE/g DW, percent recoveries for each method were calculated. In CSE, TFC ranged from 0.42 ± 0.08 to 2.63 mg QE/g DW with 4.93 % to 30.55 % recovery; while TPC ranged from 2.09 ± 1.07 to 6.15 mg GAE/g DW with 23.31 % to 68.72 % recovery. In MAE, TFC ranged from 1.20 ± 0.21 to 2.98 ± 0.34 mg QE/g DW with 13.45 % to 34.67 % recovery; while TPC ranged from 3.10 ± 0.22 to 4.24 ± 0.75 mg GAE/g DW with 34.62 % to 42.30 % recovery. Higher TFC was obtained with MAE, while higher TPC was obtained with CSE. Lastly, MAE was cheaper for flavonoid extraction, while CSE was cheaper for phenolic extraction.

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