Analysis of Phytochemical Composition and Antioxidant Activities of Aqueous and Methanol Extracts of Black, Green, Purple, and White Teas Grown in Kenya

Abstract

Abstract Background Tea, a widely consumed beverage worldwide increasingly elicits interest due to reported high levels of polyphenols. Polyphenols have been extensively investigated, as they are a potential source of natural antioxidants. Methods The aim of the study was to determine and compare the phytochemical composition and antioxidant activities of aqueous and methanol extracts of black, green, purple, and white teas found in selected regions of Kenya.A total of 56 samples were obtained from tea classified as black, green,purple, and white tea in various factories. The samples were then grounded and extracted using methanol and de-ionized water for 48 hours. The composition of phenolic and tannin contents was determined using Folin- Ciocalteu method. Flavonoids content was determined through the formation of the flavonoids– aluminum complex assay. Antioxidant activity was determined through the DPPH scavenging activity and the iron-reducing power of the extracts. Results The phenolic contents in all samples were significantly higher than flavonoid and tannin levels. In samples extracted with water, the phenolic contents were high (41.74 ± 5.25) mg/g, while flavonoid (0.58 ± 0.06 mg/g) and tannin levels (2.47 ± 0.79) mg/g were relatively low. There was a negative correlation between phytochemicals and the antioxidant activity of the various teas. Conclusions The findings suggest that the different teas have high levels of phytochemicals and are natural antioxidants, however there is no significant variation at p = 0.05 in the composition of phytochemical compounds among the different tea groups.