Chemical profile and antioxidant potential of extractable and non‐extractable polyphenols in commercial teas at different fermentation degrees

Abstract

The present study aimed to compare the chemical and antioxidant differences between the extractable and non‐extractable polyphenols (EPP and NEPP) in commercial teas with different fermentation degrees. The results showed that both content and antioxidant activity of NEPP were lower than EPP regardless of fermentation degrees of teas. One white tea, Baekho Silver Needle (BSN), had the highest NEPP content (58.38 ± 0.73 mg GAE/g DW) by alkaline hydrolysis, as well as the antioxidant activities among different teas studied. Meanwhile, alkaline hydrolysis also was the most effective method in extracting the NEPP from these teas, followed by acid and enzymatic hydrolysis. Combined principle component analysis and hierarchical clustering analysis demonstrated that gallic acid (GA), epigallocatechin (EGC), and gallocatechin (GC) were three major components in the NEEP studied, with the highest content 13.89 ± 0.87 mg/g DW in BSN, 16.14 ± 1.24 mg/g DW in Dianhong (DH), and 7.26 ± 0.55 mg/g DW in Biluochun (BLC), respectively. GA also was found to be the main contributor to antioxidant activity of NEPP. In addition, NEPP with different fermentation degrees showed discriminations in total polyphenols content, phytochemical profiles, and antioxidant activities but were disorder with the fermentation degrees of these teas. These results provided more information for NEPP in teas with different fermentation degrees including the phytochemical profiles and optimal extraction method. Practical applications NEPP have long been underestimated or neglected because this part of polyphenolic fraction cannot be extracted from the residues by aqueous or organic solvents. This study systematically investigated phytochemical profiles and antioxidant activity of EPP and NEPP in commercial teas with different fermentation degrees. Comparing the release efficacy of tea NEPP by different extraction methods indicated that tea residues were still a considerable source for NEPP. Profiles of polyphenols in teas with different fermentation degrees can be better uncovered according to this study to improve the health.

Colon-Targeted Release of Turmeric Nonextractable Polyphenols and Their Anticolitis Potential via Gut Microbiota-Dependent Alleviation on Intestinal Barrier Dysfunction in Mice

“…15,18,22 The total polyphenol contents of EPs, NEPs, and DFs were measured using the Folin− Ciocalteu method according to the previous method with slight modifications. 24 Soluble sugars in NEPs and DFs were extracted using deionized water and spectrophotometrically quantified using the phenol−H 2 SO 4 assay. 25 Total and insoluble fibers in NEPs and DFs were determined by the enzymatic−gravimetric method, and the soluble fibers were calculated as the difference between total fibers and insoluble fibers.…”

“…Besides, the NEPs were further extracted using alkaline hydrolysis by 2 mol NaOH solution at 85 °C/4 h. The extracting solution was adjusted to pH = 2 with 6 mol hydrochloric acid and then centrifuged at 6000 g for 5 min. The supernatant was extracted with ethyl acetate and then evaporated to obtain the bound polyphenols released from NEPs, while the remanent DF-enriched residue was denominated as DFs. ,, The total polyphenol contents of EPs, NEPs, and DFs were measured using the Folin–Ciocalteu method according to the previous method with slight modifications . Soluble sugars in NEPs and DFs were extracted using deionized water and spectrophotometrically quantified using the phenol–H 2 SO 4 assay .…”

“…Notably, recent studies have suggested that the healthy benefits of bound polyphenols as macromolecules are more effective in the colon, including anti-inflammatory, antioxidant, and gut microflora-based regulatory effects. – Besides, the released DFs may be metabolized into short-chain fatty acids (SCFAs) by the colon microbiota to participate in the improvement of intestinal inflammation and epithelial barrier damage . Recently, NEPs from grape peels and strawberries are demonstrated to exhibit significant preventive effects on colitis and colon cancer. , However, the colon-targeted release properties and microecological nutritional effects of turmeric NEPs mostly as DF-bound polyphenols are yet unclear.…”

Natural Polyphenols for the Preservation of Meat and Dairy Products

“…Commercial teas were evaluated for their contents and antioxidant activity in a recent study comparing extractable and non-extractable polyphenols. The results indicate that both the antioxidant activity and contents of extractable polyphenols were found to be higher than those of the non-extractable polyphenols [ 50 ]. Theaflavin is another polyphenol extracted from black tea.…”

Pressurized Liquid Extraction Combined with Enzymatic-Assisted Extraction to Obtain Bioactive Non-Extractable Polyphenols from Sweet Cherry (Prunus avium L.) Pomace

“…NEPs have been shown to possess high antioxidant, antihypertensive, and antidiabetic properties [ 7 , 8 , 9 ]. NEPs comprise different classes of phenolic compounds such as phenolics with high molecular weight or simple phenols associated with macromolecules, like proteins, in the cell wall [ 10 ]. These compounds remain in the residue obtained by conventional extraction due to their strong interactions with the cell wall.…”