Extraction of Proanthocyanidins from Chinese Wild Rice (<i>Zizania latifolia</i>) and Analyses of Structural Composition and Potential Bioactivities of Different Fractions

• Main Authors: Mei-Jun Chu, Yong-Mei Du, Xin-Min Liu, Ning Yan, Feng-Zhong Wang, Zhong-Feng Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2019-04-01
• Series: Molecules
• Subjects: wild rice; <i>Zizania latifolia</i>; proanthocyanidins; extraction; purification; fractionation; degree of polymerization; bioactivities
• Online Access: https://www.mdpi.com/1420-3049/24/9/1681

Due to the importance of proanthocyanidin bioactivity and its relationship with chemical structure, ultrasound-assisted extraction and purification schemes were proposed to evaluate the proanthocyanidin content and analyze the structural composition and potential bioactivities of different proanthocyanidin fractions from Chinese wild rice (<i>Zizania</i> <i>latifolia</i>). Following an optimized extraction procedure, the crude wild rice proanthocyanidins (WRPs) were purified using n-butanol extraction, chromatography on macroporous resins, and further fractionation on Sephadex LH-20 to yield six specific fractions (WRPs-1&#8722;WRPs-6) containing proanthocyanidin levels exceeding 524.19 &#177; 3.56 mg/g extract. Structurally, (+)-catechin, (&#8722;)-epicatechin, and (&#8722;)-epigallocatechin were present as both terminal and extension units, and (&#8722;)-epicatechin was the major extension unit, in each fraction. This is the first preparation of WRP fractions with a different mean degree of polymerization (mDP), ranging from 2.66 &#177; 0.04 to 10.30 &#177; 0.46. A comparison of the bioactivities of these fractions revealed that fractions WRPs-1&#8722;WRPs-5 had significant DPPH radical scavenging activities, whereas fraction WRPs-6 with a high mDP showed better &#945;-glucosidase and pancreatic lipase inhibitory effects. These findings should help define possible applications of WRPs to functional foods or nutraceuticals.