Radical Scavenging of White Tea and Its Flavonoid Constituents by Electron Paramagnetic Resonance (EPR) Spectroscopy

Abstract

White tea (WT) presents high levels of catechins, which are known to reduce oxidative stress. WT is the least processed tea, unfermented and prepared only from very young tea leaves. The subject of this paper is the use of the spin trap method and electron paramagnetic resonance (EPR) spectroscopy as the analytical tool to measure, for the first time, the radical scavenging activity of WT and its major catechin components, epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG), against the methoxy radical, using ferulic acid as antioxidant pattern. The antioxidant activity has been measured by the decrease of the intensity of the spectral bands of the adduct DMPO-OCH3 in the EPR with the amount of antioxidant in the reactive mixture. Tea leaves and buds were extracted with waterless methanol. It has been proved that tea compounds with more antiradical activity against methoxy radical are those with the gallate group, EGCG and ECG.

Dynamic changes in flavonol glycosides during production of green, yellow, white, oolong and black teas from Camellia sinensis L. (cv. Fudingdabaicha)

“…The bitterness and astringency of green tea may still be unacceptable to many people, thus white, yellow and oolong teas with mellow taste and less bitterness potentially substitute for people who are interested in consuming polyphenols. The physiological functionalities of white, yellow and oolong teas have been reported (Lopez & Calvo, 2011;Azman et al, 2014). It is worthwhile to investigate the effect of manufacturing procedure on the chemical composition of different types of teas.…”

Optimization of ultrasound‐assisted extraction of grape‐seed oil to enhance process yield and minimize free radical formation

“…In this method, suitable diamagnetic molecules that are capable of capturing radicals are added to samples. The spin‐trapping agents react with the free radicals to form more stable radicals, which are detectable by EPR …”

“…The spin-trapping agents react with the free radicals to form more stable radicals, which are detectable by EPR. 14 Because grape seed is a relatively abundant source of oil and bioactive compounds, there is a need to look for an alternative process to reuse grape seed. Hence, this study aimed to optimize ultrasound-assisted extraction of grape-seed oil to obtain a higher process yield and lower content of free radicals in the oil.…”

Effect of water quality on the main components in Fuding white tea infusions

“…White tea has been reported to possess many health benefits, including antioxidant (Damiani et al 2014), antibacterial (Tomaszewska et al 2015), and anti-cancer (Hajiaghaalipour et al 2015) effects, as well as other properties (Song et al 2015). The strong antioxidant capacity of white tea is connected with its high catechin content (Azman et al 2014). Catechins such as epigallocatechin gallate (EGCG), epigallocatechins (EGC), epicatechin gallate (ECG), and epicatechin (EC) are the principal bioactive compounds present in tea (Chen et al 2010;Narukawa et al 2010Narukawa et al , 2011.…”