Simultaneous Optimal Production of Flavonol Aglycones and Degalloylated Catechins from Green Tea Using a Multi-Function Food-Grade Enzyme

Chan-Su Rha,Shin-Woo Kim,Dae-Ok Kim,Yong Deog Hong,Kyoung Hee Byoun

doi:10.3390/catal9100861

Chan-Su Rha, Shin-Woo Kim + Show 3 more

Open Access

https://doi.org/10.3390/catal9100861

Copy DOI

Abstract

(1) Background: Green tea (GT) contains well-known phytochemical compounds; namely, it is rich in flavan-3-ols (catechins) and flavonols comprising all glycoside forms. These compounds in GT might show better biological activities after a feasible enzymatic process, and the process on an industrial scale should consider enzyme specificity and cost-effectiveness. (2) Methods: In this study, we evaluated the most effective method for the enzymatic conversion of flavonoids from GT extract. One enzyme derived from Aspergillus niger (molecular weight 80–90 kDa) was ultimately selected, showing two distinct but simultaneous activities: intense glycoside hydrolase activity via deglycosylation and weak tannin acyl hydrolase activity via degalloylation. (3) Results: The optimum conditions for producing flavonol aglycones were pH 4.0 and 50 °C. Myricetin glycosides were cleaved 3.7–7.0 times faster than kaempferol glycosides. Flavonol aglycones were produced effectively by both enzymatic and hydrochloride treatment in a time-course reaction. Enzymatic treatment retained 80% (w/w) catechins, whereas 70% (w/w) of catechins disappeared by hydrochloride treatment. (4) Conclusions: This enzymatic process offers an effective method of conditionally producing flavonol aglycones and de-galloylated catechins from conversion of food-grade enzyme.

Highlights

Green tea (GT) is well-known to be enriched in catechins with flavonols/flavones as the second-most dominant flavonoids; these include myricetin, quercetin, apigenin, and kaempferol [1]
All of the enzymes were derived from the broth of Aspergillus spp., the significant activities differed depending on the culture conditions
gallic acid (GA) is an indicator of tannin acyl hydrolase activity, which promotes the degalloylation of gallated catechins

Summary

Introduction

Green tea (GT) is well-known to be enriched in catechins with flavonols/flavones as the second-most dominant flavonoids; these include myricetin, quercetin, apigenin, and kaempferol [1]. GT generally contains approximately 15% catechins and 0.4% flavonols on a dry weight basis [2]. In human nutrition, GT flavonols are generally considered to be less crucial for the utility and functionality of GT. The content and compositions of flavonol and flavone glycosides vary according to GT cultivar [5,6]. Glycosylated flavonols and flavones have different sugar bonds and compositions according to the plants [7]. The glycosidic structure of flavonols affects their biological and physiological properties, such as digestive stability and bioaccessibility [8,9,10]

Results

Discussion

Conclusion