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

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.

Comparison and correlation analysis of flavonoids and chlorogenic acid contents in different strains of Acer truncatum

“…Therefore, the actual content of TFC should be lower than that indicated by our data. However, using the same method used in our study, Lee et al (2016) and Bizuayehu et al (2016) determined the TFC in green tea and obtained highly similar results (2320 and 2340 mg catechin equivalent/100 g, respectively). Ot could be concluded that the total flavonoids in ATLs (mg/100 g) were similar to those in green tea and that ATLs were suitable for processing green tea for drinking.…”

In vitro antioxidant activity and polyphenolic content of commonly used spices from Ethiopia

“…adoensis were reported to possess analgesic activity ( Makonnen et al., 2003 ) and anti-pyretic activity ( Debell et al., 2005 ). The antioxidant properties in tandem with terpenoid contents of the essential oil of some of these spices have been reported by some researchers (e.g., Sishu et al., 2005 ; Eyob et al., 2008 ; Menghesa et al., 2011 ; Hailemariam and Shimelis, 2013 ; Bizuayehu et al., 2016 ; Debebe et al., 2018 ; Simur, 2018 ). However, antioxidant properties of these spices were not comparatively investigated from a standpoint of their phenolic contents.…”

Subcritical Water Extraction of Chestnut Bark and Optimization of Process Parameters

“…The Folin–Dennis method [ 34 ] was used for the determination of total tannin content in extracts [ 36 ]. To 1 mL of extract, 2.5 mL of Folin–Dennis reagent (diluted with water 1:10) and 2 mL of Na 2 CO 3 solution (75 g/L) were added.…”