Comparative Analysis of the Polyphenols, Caffeine, and Antioxidant Activities of Green Tea, White Tea, and Flowers from Azorean Camellia sinensis Varieties Affected by Different Harvested and Processing Conditions.

Lisete Paiva,Clara Rego,Elisabete Lima,José Baptista,Massimo Marcone

doi:10.3390/antiox10020183

Lisete Paiva, Clara Rego + Show 3 more

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https://doi.org/10.3390/antiox10020183

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Journal: Antioxidants	Publication Date: Jan 27, 2021
Citations: 23	License type: CC BY 4.0

Affiliation: University of the Azores, University of Guelph

Abstract

This study evaluates the polyphenol profiles as well as caffeine (dry weight basis), and antioxidant activities of green tea (GTs), white tea (WTs), and flowers (Fl) samples from Azorean Camellia sinensis varieties affected by different harvested and processing conditions. Epicatechins derivatives, determined by RP-HPLC/PDAD, presented higher values in GTs with respect to WTs, decreasing as follows: epigallocatechin-3-gallate > epicatechin-3-gallate ≫ epicatechin ≫ epigallocatechin, and higher values in summer and early autumn than in spring. This was also accompanied by an in consistent withering time pattern. Esterified catechins were higher in all samples (100.8–312.3 mg/g) with respect to non-esterified catechins (15.1–37.7 mg/g). Caffeine (6.2–27.7 mg/g) decreased as follows: WTs > GTs ≫ Fl, and inconsistent seasonal and withering patterns were observed among the WTs. Total phenolics (125.9–295.4 mg gallic acid equivalents/g dried extract) and total flavonoids (35.2–69.7 mg rutin equivalents/g dried extract), determined by Folin–Ciocalteu and colorimetric methodologies, were higher in GTs than in WTs and Fl. Concerning the antioxidant patterns, the free radical scavenging activity (FRSA) and ferric reducing antioxidant power (FRAP) presented EC50 values ranges from 3.6 to 17.3 µg/mL and 4.8 to 16.5 µg/mL, respectively, and ferrous ion-chelating (FIC) activity ranged from 47.1 to 82.8%, highlighting that FRSA was better than butylated hydroxytoluene (BHT). Tea leaves exhibited, in general, higher activities with respect to tea Fl, and the WT sample plucked in summer and withered for 23 h showed the highest FRAP and FIC activity. In conclusion, this study shows the characteristic variation of GTs, WTs, and Fl of two tea varieties and may support crop quality improvement and promote the valorization of tea Fl.

Highlights

It is well documented that the catechins present in fresh leaves of C. sinensis remain practically unchanged in commercial green tea (GT) when appropriate manufacturing processes are employed, except for a few enzymatically catalyzed changes that occur rapidly
The sample yields obtained from the studied samples are as16follows: 20.02–22.26%, 14.89%, and 18.60% for white tea (WT), flowers, and average of GTs, respectively, highlighting that WT and GT samples presented higher yield values with respect topractically flowers sample
The extraction protocol and analysis using a methodology based upon RP-HPLC/PDAD

Summary

Introduction

Tea polyphenols (TPs), the catechins group, are considered key contributors to the protective effects that GT possess against several diseases (e.g., cancer, cardiovascular disease, liver disease, type 2 diabetes, and neurodegenerative diseases) as well as the ageing process, due to their diverse pharmacological activities, in particular, their strong antioxidant properties (for recent reviews, see [3,4,5,6]). In addition to their antioxidant activity, tea catechins have anti-inflammatory properties and have been shown to have an effect on the increased uptake of glucocorticoids in lungs diseases and, tea catechins supplementation may be beneficial as therapeutic strategies against COVID-19 [7,8]

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