Grape seed proanthocyanidin (GSP) is a natural food antioxidant. Natural proanthocyanidins (PC) in grape seed are usually polyhydroxy derivatives which exhibit hydrophilic character. GSP was modified structurally to improve its lipophilicity, expand its application in lipophilic media, and enhance its cellular absorption in vivo. Esterification of the water-soluble GSP was prepared by immobilized lipase Lipozyme TL IM with lauric acid, and their enhanced lipophilicity was confirmed by the 1-octanol/water partition coefficient. The presence of mono-, di-, and trilauroylated derivatives in GSP derivatives was confirmed by HPLC-MS-MS, and four lauroylated derivatives were identified as 3',5'-2-O-lauroyl epigallocatechin, 3'-O-lauroyl catechin, 3'-O-lauroyl epicatechin, and 3',3″,5″-3-O-lauroyl epicatechin gallate by NMR. GSP derivatives exhibited the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC of 41 μg/mL) compared to that of GSP, hydroxytoluene (BHT), and tert-butyl hydroquinone (TBHQ). The results suggest that GSP derivatives may be used as potential lipophilic antioxidants in the food industry.
Natural antioxidants such as polysaccharides with strong antioxidant activities are used to protect against oxidative damage, yet little is known so far about the antioxidant effects of litchi fruit polysaccharides. In the present study, four different polysaccharide-enriched fractions were isolated from litchi pulp tissue and partially purified by a stepwise method of ethyl alcohol (EtOH) precipitation. Their chemical and physical characteristics were determined by chemical methods, gas chromatography and IR spectrophotometry. Antioxidant activities of these fractions were investigated using various in vitro assay systems. These four polysaccharide-enriched fractions exhibited a dose-dependent free radical scavenging activity as shown by their DPPH radical, superoxide anion and hydroxyl radical inhibition, chelating ability and reducing power. Among the different fractions, LFP-III showed the strongest scavenging activity against DPPH radical, superoxide and hydroxyl radicals and chelating ability. These findings suggest litchi polysaccharides from pulp tissue have potential as functional foods with enhanced antioxidant activity.
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