Structural Elucidation of Novel Stable and Reactive Metabolites of Green Tea Catechins and Alkyl Gallates by LC-MS/MS

Abstract

Synthetic gallic acid derivatives are employed as additives in food, personal care products, and pharmaceutical formulations. Despite their widespread use, little is known about their human exposure, health effects, and metabolism. Green tea catechins are natural antioxidants, known for their health-promoting properties, and are also employed as food additives or in personal care products. The objective of this study was to establish metabolic pathways involved in the biotransformation of green tea catechins and synthetic gallate esters. Liquid chromatography coupled with high-resolution tandem mass spectrometry (LC-HRMS/MS) was used to elucidate oxidative and methylated metabolites, in addition to glutathione conjugates, formed in vitro using human liver microsomal incubations. The developed method was applied to 14 different parent compounds with a wide range of polarities, for the structural elucidation of many known and novel metabolites. These results serve to inform about the wide variety of possible metabolites formed upon exposure to these compounds.

Antioxidant Effects of Catechins (EGCG), Andrographolide, and Curcuminoids Compounds for Skin Protection, Cosmetics, and Dermatological Uses: An Update

“…[ [24][25][26][27][28][29][30][31][32][33][34][35] Extract of dried leaves Main compounds: catechins, polyphenols, or flavan-3-ols. [64,65] EGCG (65% of total catechins) depending on drying conditions and extraction process. [65,66] Extraction of Catechins with polar organic solvents OR Good extraction but unusable for cosmetics.…”

“…[64,65] EGCG (65% of total catechins) depending on drying conditions and extraction process. [65,66] Extraction of Catechins with polar organic solvents OR Good extraction but unusable for cosmetics. Pharmacomodulations to increase the stability and bioavailability Alkylated gallate esters, which retain very good antioxidant power and better bioavailability but have shown cytotoxicity in rats.…”

“…Pharmacomodulations to increase the stability and bioavailability Alkylated gallate esters, which retain very good antioxidant power and better bioavailability but have shown cytotoxicity in rats. [28,65] Increased skin penetration with various formulations: chitosan microparticles (<5 mm) loaded with green tea extracts Better skin permeability for non-galloylated catechins such as EGC and EC. Lower permeability for galloylated analogues of EGCG and ECG.…”

“…Camellia sinensis is of considerable interest for its health benefits, as its extracts contain a variety of catechin polyphenols or flavan-3-ols, which account for over 30% of the weight of dried leaves [64,65] and are responsible for green tea's activities. Although epigallocatechin-3-gallate (EGCG) is the most abundant catechin (around 65% of total catechins), green tea also contains significant amounts of other catechins: epicatechin, epicatechin-3-gallate, and epigallocatechin [65] (Table 1). The quantities and levels of polyphenols depend on the tea variety, growing conditions (i.e., the environment), drying conditions, and extraction process [66].…”

“…Polyphenols can also undergo rapid degradation, and pharmacomodulations have been carried out to increase the stability and bioavailability of these antioxidants. Although these alkylated gallate esters (Table 1) showed very good antioxidant properties and increased bioavailability, some of them also showed cytotoxicity in rats [28,65].…”