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Preparation of Free, Soluble Conjugate, and Insoluble‐Bound Phenolic Compounds from Peels of Rambutan ( Nephelium lappaceum ) and Evaluation of Antioxidant Activities in vitro
Author(s) -
Sun Liping,
Zhang Huilin,
Zhuang Yongliang
Publication year - 2012
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2011.02548.x
Subject(s) - chemistry , gallic acid , conjugate , syringic acid , rambutan , caffeic acid , antioxidant , extraction (chemistry) , hydrolysis , fraction (chemistry) , chromatography , food science , organic chemistry , mathematical analysis , mathematics
The soluble phenolic compounds of rambutan peels (RP) were extracted by microwave‐assisted extraction (MAE) and the operating parameters were optimized. The optimal conditions obtained were ethanol concentration of 80.85%, extraction time of 58.39 s, and the ratio of liquid to solid of 24.51:1. The soluble phenolic content by MAE was 213.76 mg GAE/g DW. The free, soluble conjugate, and insoluble‐boaund phenolic compounds were prepared by alkaline hydrolysis, and the contents of 3 fractions were 185.12, 27.98 and 9.37 mg GAE/g DW, respectively. The contents of syringic acid and p ‐coumaric acid were high in the free fraction, showing 16.86 and 19.44 mg/g DW, and the soluble conjugate and insoluble‐bound phenolics were mainly composed of gallic acid and caffeic acid. Furthermore, the antioxidant activities of 3 fractions were evaluated in 5 model systems. Results indicated that the free fraction had high antioxidant activities, compared with the soluble conjugate and insoluble‐bound fractions.