Polyphenols, flavonoids and (-)-epigallocatechin gallate in tea leaves and in their infusions under various conditions

Abstract

Purpose – The purpose of this paper was to determine total polyphenols (TP), total flavonoids (TF) and (-)-epigallocatechin gallate (EGCG) in five commercial tea extracts and in their infusions at various temperatures (95-60°C) and brewing times (5-30 min). Design/methodology/approach – TP was determined by the Folin–Ciocalteu method, TF by the aluminium chloride colorimetric method and EGCG by HPLC method. Findings – The results showed that White tea – Silver needle had the highest content of TP and EGCG when extracted, but its infusions had very poor concentrations of these compounds. Green tea infusion was better source of TP and EGCG than white or black tea, although its extract did not contain a very high amount of TP compared to the latter two types. Black tea extract had a relatively high content of TP and TF in its extract. Its infusions as well contained higher concentrations of TP than white tea, but lower concentrations of EGCG than all studied teas. Originality/value – Increasing infusion time and temperature does not necessarily increase the concentration, according to the results. To the authors’ knowledge, this is the first report on comparing these types of tea, especially the white tea, with other well-known teas under various infusion conditions. The extraction of the white tea leaves was also not found in previous works.

Phytochemical Analysis, Total Phenolic Content, Hemolytic and Antihemolytic Activities of Centaurea iberica (Asteraceae)

“…TPC in the hydromethanolic extract of C. iberica was determined by the Folin-Ciocalteu method as described by (Alhafez et al, 2014): 4.8 ml of distilled water was added to 1ml of the extract, followed by addition of 4 ml of sodium carbonate Na 2 CO 3 (2%) and 200 µl of Folin-Ciocalteu reagent. The mixture was incubated for 60 min at 25°C.…”

Composition and Antioxidant Activity of Vitex agnus-castus L. and Rosmarinus Officinalis L. Leaves Essential Oils Cultivated in Syria

“…Total phenolic contents of the essential oils were determined by employing the methods given in the literature [23,24], involving Folin-Ciocalteu reagent and Gallic acid (Sigma) as standard. The absorbance was measured at 760 nm (λ max) using the previous spectrophotometer against a blank.…”

“…Total flavonoids contents of the essential oils were determined according to the aluminium chloride colorimetric method as described by [23,25].The absorbance of the reaction mixture was measured at 440 nm (λ max) using the previous spectrophotometer against a blank. A calibration curve of quercetin solutions was prepared in 70% ethanol (0-100 mg/L and R2 = 0.9999) and the data were expressed as quercetin equivalents.…”

Inovasi Produk Citrus Infused Honey Tea Dengan Penambahan Rosela (Hibiscus Sabdariffa Linn.) (Kajian Konsentrasi Rosela Dan Lama Infusing)

“…Berdasarkan hasil analisis fisik dapat diketahui bahwa pekatan maupun seduhan citrus infused honey tea memiliki warna merah yang berasal dari kandungan antosianin dengan total kandungan sebesar 445 mg/100 g berat kering (Chumsri et al, 2008;AlHafez et al, 2014;Zhang dan Ruan, 2016). Total padatan terlarut pada pekatan dan seduhan CIHT berasal dari madu dengan kadar gula tinggi dan adanya penambahan bahanbahan lain seperti jeruk, kayu manis, dan rosela.…”