| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 104 === Bawang Dayak or Dayak onion bulb (Eleutherine palmifolia L. Merr) possesses antioxidant characteristics and is considered as a medicinal plant. The effect of different extracting solvent and condition on total yield of extract, total phenolic content (TPC), total flavonoids content (TFC), total anthocyanins content (TAC), and antioxidant activities of extract from bawang dayak was investigated in this work. Five extracting solvents were used: water, aqueous ethanol, aqueous methanol, acetone, and ethyl acetate. Three methods: agitation (using magnetic stirrer, 500 rpm, for 1, 12 and 24 h), ultrasound-assisted (40 kHz, for 20 and 60 min), and combining methods of agitation and ultarsonication were conducted at various temperatures (30, 40, 50, 60, and 70oC).
The antioxidant activities of extracts were measured using different in vitro antioxidant assays. Diphenyl-1-picrylhydrazyl (DPPH) method was used to determine the antioxidant activities of extracts, and IC50 of the extracts were determined. TPC, TFC, TAC of extracts were determined using Follin-Ciocalteu method, aluminium chloride colorimetric method, and pH differential method, respectively.
Aqueous 70% methanol was found as the most effective solvent to yield extract with the highest TPC, TFC, TAC, and antioxidant activities. Phenolic content and antioxidant activities of extracts increased gradualy and significantly with increasing of extraction temperature. Ultrasound-assissted extraction with agitation was found as the most efficient extraction method. The yield of phenolic content and antioxidant activities of extract obtained from the agitation extraction process performed at 30oC for one hour were the lowest among all experiment condition tested.
On the whole, this work suggests that the application of ultrasound inproves the efficiency and/or the yield of the extraction process.
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