Low-Cost Ru/C-Catalyzed Depolymerization of the Polymeric Proanthocyanidin-Rich Fraction from Bark To Produce Oligomeric Proanthocyanidins with Antioxidant Activity

Abstract

A new method has been developed for the high-value utilization of larch bark, which is regarded as a low-value byproduct of the logging industry. Polymeric proanthocyanidins (PPCs) were extracted from the Larix gmelinii bark and depolymerized by catalytic hydrogenolysis, using ruthenium/carbon (Ru/C) as the catalyst. The method has been found that although the molecular weight of the depolymerized product was significantly lower, the basic structural units were not destroyed, and the product retained a condensed flavanol polyphenol structure; the depolymerized product contains very little Ru metal and thus complies with food safety standards; the antioxidant properties of both the depolymerized products and PPCs were better than those of the commonly used antioxidant 2,6-di-tert-butyl-4-methylphenol. The relative molecular weight and steric hindrance of the depolymerized products were lower than those of the PPCs, leading to better antioxidant performance. A new technical route for the depolymerization of PPCs from the L. gmelinii bark is provided. The route offers practical and commercial advantages, and the product could have many applications as an antioxidant.

Insight in the Recent Application of Polyphenols From Biomass

“…Additionally, Xu et al (2009) studied the effect of pomegranate flower extract on hepatic fat accumulation in Zucker diabetic obese rats with severe fatty liver disease and highlighted the hypolipidemic effect of the isolated polyphenols. Yu et al (2014) found that pomegranate leaves (PGL) have a similar modulating effect on lipid metabolism. Pomegranate leaves and their major active components (ellagic acid, gallic acid, pyrogallic gallic acid, and tannic acid) showed the effect of inhibiting pancreatic lipase activity in vitro.…”

A Food-Grade Method for Enhancing the Levels of Low Molecular Weight Proanthocyanidins with Potentially High Intestinal Bioavailability

“…Although several methods for depolymerization of PACs are described in the literature, only some of them are applicable in the agri-food industry. In a study published by Zhu et al [ 39 ], it was reported that ruthenium/carbon-catalyzed depolymerization of polymeric PACs from larch bark resulted in a valuable increase in terms of oligomeric PACs. Moreover, Zhang et al [ 40 ] have described an innovative method based on the steam explosion treatment of grape seeds aimed at depolymerizing polymeric PACs into oligomeric ones.…”

Nickel-Catalyzed Reductive Deoxygenation of Diverse C–O Bond-Bearing Functional Groups

“…Substrate 58 is a useful model compound for the α- O -4 linkage found in lignin; of the eight distinct C–O bonds present in this substrate, we found that the benzylic position could be selectively cleaved to reveal the two arene products 59 and 60 in 86 and 81% yields, respectively (Scheme c). Tannins are another class of naturally abundant aromatic biomolecules that may serve as useful feedstock molecules in the bioeconomy . Exposing polyoxygenated tannin (−)-epicatechin 61 to this protocol allowed for the recovery of product 62 upon employing KF as a base rather than KO t Bu.…”