Determination of Tea Components with Antioxidant Activity

Abstract

Levels of essential elements with antioxidant activity, as well as catechins, gallic acid, and caffeine levels, in a total of 45 samples of different teas commercialized in Spain have been evaluated. Chromium, manganese, selenium, and zinc were determined in the samples mineralized with HNO 3 and V 2 O 5 , using ETAAS as the analytical technique. The reliability of the procedure was checked by analysis of a certified reference material. Large variations in the trace element composition of teas were observed. The levels ranged from 50.6 to 371.4 ng/g for Cr, from 76.1 to 987.6 µg/g for Mn, from 48.5 to 114.6 ng/g for Se, and from 56.3 to 78.6 ng/g for Zn. The four major catechins [(-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)], gallic acid (GA), and caffeine were simultaneously determined by a simple and fast HPLC method using a photodiode array detector. In all analyzed samples, EGCG ranged from 1.4 to 103.5 mg/g, EGC from 3.9 to 45.3 mg/g, ECG from 0.2 to 45.6 mg/g, and EC ranged from 0.6 to 21.2 mg/g. These results indicated that green tea has a higher content of catechins than both oolong and fermented teas (red and black teas); the fermentation process during tea manufacturing reduces the levels of catechins significantly. Gallic acid content ranged from 0.039 to 6.7 mg/g; the fermentation process also elevated remarkably gallic acid levels in black teas (mean level of 3.9 ( 1.5 mg/g). The amount of caffeine in the analyzed samples ranged from 7.5 to 86.6 mg/g, and the lower values were detected in green and oolong teas. This study will be useful for the appraisal of trace elements and antioxidant components in various teas, and it will also be of interest for people who like drinking this beverage.KEYWORDS: Tea; trace elements; catechins; gallic acid; antioxidants; caffeine INTRODUCTIONTea, a leaf extract of the plant Camellia sinensis, is the second most consumed beverage in the world, with an estimated 18-20 billion cups consumed daily and, for instance, an estimated average consumption of 1 L/person/day in the United Kingdom (1). Depending on the manufacturing process, teas are classified into three major types: nonfermented green tea (produced by drying and steaming the fresh leaves and thus, no fermentation, i.e., oxidation, occurs); semifermented oolong tea (produced when the fresh leaves are subjected to a partial fermentation stage before drying); and fermented black and red (pu-erh) teas (which undergo a full fermentation stage before drying and steaming, although the fermentation of black tea is oxidation and that of pu-erh tea is attained using microorganisms) (2).Originating from China, tea has gained the world's taste in the past 2000 years. Initially, it was consumed only by Chinese monks, but its use spread to other regions, such as Great Britain, which allowed its effective diffusion to Western countries. Nowadays, consumption of tea is part of people's daily routine, as an everyday drink and as a therapeutic aid in m...

Antioxidant and Antibacterial Activity of the Beverage Obtained by Fermentation of Sweetened Lemon Balm (Melissa officinalis L.) Tea with Symbiotic Consortium of Bacteria and Yeasts

“…(36). Caff eine, epigallocatechin gallate and epigallocatechin are mentioned as the main compounds in black tea methanolic extracts (37,38). Certain diff erences in tea composition are expected and infl uenced by a number of factors such as species, season, age of the leaves, climate, and horticultural conditions (38).…”

“…Caff eine, epigallocatechin gallate and epigallocatechin are mentioned as the main compounds in black tea methanolic extracts (37,38). Certain diff erences in tea composition are expected and infl uenced by a number of factors such as species, season, age of the leaves, climate, and horticultural conditions (38). It has been found that the environment, especially climate, has a signifi cant eff ect on the biosynthesis of catechins and that the formation of chlorophyll during young leaf development takes part in the regulation of individual proportions of catechins in tea (39).…”

Comparison of Infusions from Black and Green Teas (Camellia sinensis L. Kuntze) and Erva-mate (Ilex paraguariensis A. St.-Hil.) Based on the Content of Essential Elements, Secondary Metabolites, and Antioxidant Activity

“…This positive impact on the human organism is caused by antioxidant properties of polyphenolic compounds that are present in tea infusions, among them phenolic acids (Ronowicz et al 2014;Salahinejad and Aflaki 2010). Other chemical constituents in C. sinensis tea consist of volatile compounds, alkaloids, vitamins, carbohydrates, amino acids, proteins, chlorophyll, fluoride, minerals, and trace elements (Carbera et al 2003). Polyphenols are compounds of great interest because they have potent antioxidant activity both in vitro and in vivo due to its reducing properties (Wu and Wei 2002).…”

Influence of Geographical Regions on Catechin and Caffeine Levels in Tea (<i>Camellia sinensis</i>)

“…Catechins are among the major polyphenolic compounds in the tea plant constituting up to 30% of the dry weight in a freshly picked tea leaf [3]. Catechins have been reported to be potent biomolecules responsible for the health benefits associated with regular drinking of tea [4] [5]. Studies have shown that catechins possess beneficial physiological activities such as antioxidants [6] [7], hypocholesterolemiant [8] [9], anti-atherosclerotic [10], anti-inflammatory [11], and anti-HIV activities [12].…”