Abstract
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 (Zizania latifolia). 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–WRPs-6) containing proanthocyanidin levels exceeding 524.19 ± 3.56 mg/g extract. Structurally, (+)-catechin, (−)-epicatechin, and (−)-epigallocatechin were present as both terminal and extension units, and (−)-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 ± 0.04 to 10.30 ± 0.46. A comparison of the bioactivities of these fractions revealed that fractions WRPs-1−WRPs-5 had significant DPPH radical scavenging activities, whereas fraction WRPs-6 with a high mDP showed better α-glucosidase and pancreatic lipase inhibitory effects. These findings should help define possible applications of WRPs to functional foods or nutraceuticals.
Highlights
Wild rice, the seed of the aquatic plant Zizania, has long been recognized as a health-promoting whole grain, because of its health benefits, including the ability to suppress oxidative stress, reduce hyperlipidemia, and prevent atherogenesis, type 2 diabetes, and obesity [1,2,3]
Chinese wild rice (Z. latifolia), which is widely distributed in areas along the Yangtze and Huai Rivers, is an age-old food that has been traditionally used to treat a variety of ailments in Chinese medicinal practice [2,6]
We previously revealed a high content of proanthocyanidins in Chinese wild rice [7]
Summary
The seed of the aquatic plant Zizania (family Poaceae), has long been recognized as a health-promoting whole grain, because of its health benefits, including the ability to suppress oxidative stress, reduce hyperlipidemia, and prevent atherogenesis, type 2 diabetes, and obesity [1,2,3]. Since wild rice is gluten-free and safe for human consumption, the growing interest in wild rice has increased its commercialization in North America [4]. There are four known species of wild rice. Z. aquatica, Z. palustris, and Z. texana are indigenous to North America, whereas Z. latifolia is native to China, Japan, and Vietnam [5]. Chinese wild rice (Z. latifolia), which is widely distributed in areas along the Yangtze and Huai Rivers, is an age-old food that has been traditionally used to treat a variety of ailments in Chinese medicinal practice [2,6]. Wild rice is a rich source of phenolic
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