Abstract
Conventional extraction methods of proanthocyanidins (PAC) are based on toxic organic solvents, which can raise concerns about the use of extracts in supplemented food and nutraceuticals. Thus, a PAC extraction method was developed for grape seeds (GS) and grape seed powder using food-grade ethanol by optimizing the extraction conditions to generate the maximum yield of PAC. Extraction parameters, % ethanol, solvent: solid (s:s) ratio, sonication time, and temperature were optimized by the central composite design of the response surface method. The yields of PAC under different extraction conditions were quantified by the methylcellulose precipitable tannin assay. The final optimum conditions were 47% ethanol, 10:1 s:s ratio (v:w), 53 min sonication time, and 60 °C extraction temperature. High-performance liquid chromatography analysis revealed the presence of catechin, procyanidin B2, oligomeric and polymeric PAC in the grape seed-proanthocyanidin extracts (GS-PAC). GS-PAC significantly reduced reactive oxygen species and lipid accumulation in the palmitic-acid-induced mouse hepatocytes (AML12) model of steatosis. About 50% of the PAC of the GS was found to be retained in the by-product of wine fermentation. Therefore, the developed ethanol-based extraction method is suitable to produce PAC-rich functional ingredients from grape by-products to be used in supplemented food and nutraceuticals.
Highlights
Proanthocyanidins (PAC), known as condensed tannins, are the oligomers or polymers of flavan-3-ol molecules linked together through interflavan linkages
The experimental PAC yields were fitted to a second-order polynomial response surface model, and the significance of the model components was tested by analysis of variance (ANOVA) (Table 2)
The development of an aqueous ethanol-based PAC extraction method is beneficial for the supplemented food and nutraceutical industries
Summary
Proanthocyanidins (PAC), known as condensed tannins, are the oligomers or polymers of flavan-3-ol molecules linked together through interflavan linkages. Oligomeric and polymeric PAC predominantly consist of catechin and epicatechin monomers [1]. The potential of PAC to alleviate chronic metabolic diseases has been shown by a number of studies. Supplementation of PAC has reduced obesity and obesity-associated complications by improving the blood lipid profile [9], intestinal microflora [10], and interfering adipogenesis [11]. The potential of PAC ingestion to reduce the body weight is still controversial [12]. The ability of PAC to improve vascular endothelial function and improve blood lipid profile by reducing triglyceride and low-density lipoprotein cholesterol levels is beneficial in reducing the risk of hypertension and cardiovascular diseases [13]. The microbial metabolites of PAC are proven to possess anticancer properties [18]. The interdependency of PAC and bioconverting microbes can open a new field of study to develop PAC-based synbiotics with health benefits [19]
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