Determination of some selected secondary metabolites and their invitro antioxidant activity in commercially available Ethiopian tea (Camellia sinensis).

Dereje Bizuayehu,Mirtachew Tihar Ali,Minaleshewa Atlabachew

doi:10.1186/s40064-016-2056-1

Dereje Bizuayehu, Mirtachew Tihar Ali + Show 1 more

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https://doi.org/10.1186/s40064-016-2056-1

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Journal: SpringerPlus	Publication Date: Apr 6, 2016
Citations: 27	License type: CC BY 4.0

Affiliation: Bahir Dar University

Abstract

Eight brands of tea (Camellia sinensis),which are cultivated and commercially available in Ethiopian market, were analyzed for estimation of their total secondary metabolites (polyphenols, flavonoids and tannins) content and free radical scavenging activity which is expressed on dry weight basis. In this present study, the total polyphenols, tannin and flavonoid contents were studied spectrophotometrically using Folin–Dennis, Folin–Dennis/protein precipitation and aluminium chloride methods respectively. The free radical scavenging activity was determined by using DPPH radical assay. Results of the analysis revealed that the total polyphenol content varied from 21.3 ± 0.24 to 31.6 ± 0.31 mg of gallic acid equivalent/g of dry matter. Total flavonoids content in the tea samples varied from 8.17 ± 0.68 to 23.2 ± 0.68 mg of catechin equivalent/g of dry weight and tannin content varied from 5.64 ± 0.39 7.45 ± 0.27 mg tannic acid equivalent/g of dry weight basis. The free radical scavenging activity among the tea brand samples ranged from 28.8 ± 1.86 to 80.0 ± 0.63 mg ascorbic acid equivalent/g and the half maximal inhibitory concentration (IC50%) values varied from 7.3 ± 1.35 to 64.0 ± 2.81 µg/mL of extract. The correlation between the antioxidant activity with total polyphenol content (R = 0.91325), with flavonoids (R = 0.80658) and with tannin (R = 0.73125) was calculated and maximum correlation value was found between polyphenol content and the free radical scavenging activity of the tea samples. The results in this study also revealed that green tea had the higher polyphenolic content and found to have the most promising antioxidant activity. This study further confirmed that Ethiopia tea is reach in phenolic compounds as compared to some overseas tea cultivars/varieties.

Highlights

Recent studies proven that substances from natural sources exhibits antioxidant properties that can be used to protect human beings from oxidative stress damage that could arise during physiological processes (Zeb 2015; Zeng et al 2014)
Level of total polyphenols (TPC) in different tea brands The content of total polyphenols in tea samples were derived from a standard curve of gallic acid ranging from 0.1 to 2.0 μg/mL (y = 0.01296x + 0.0093; R = 0.9913) and a standard curve of tannic acid ranging from 0.1 to 2.0 μg/mL (y = 0.00971x + 0.00845; R = 0.9957)
The results revealed that Gumero and Dire tea brands had the first and the last rank among the black tea brands in TPC and TTC respectively (Fig. 1)

Summary

Introduction

Recent studies proven that substances from natural sources exhibits antioxidant properties that can be used to protect human beings from oxidative stress damage that could arise during physiological processes (Zeb 2015; Zeng et al 2014). In the markets of world wide, three main types of tea (black tea, oolong tea, and green tea) are available based on the length of oxidation reaction and ways of processing. Black tea is the most processed and has the Bizuayehu et al SpringerPlus (2016) 5:412 greatest oxidation while Oolong tea is semi fermented or oxidized. Green tea is obtained without oxidation but with little processing stage (Pongsuwan et al 2007). Type of tea processing has significant effect on the composition of the phyto constitutes and quality and bioactivity of the beverage (Kuroda and Hara 1999; Horie et al 1993). Different varieties of green tea and processed tea are commercially available in the market recognized by the consumers

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