Studies on Phenolic Profile, Antioxidant and Anticancer Effects of Different Polar Parts of Ethanol Extract of Jinhua Tibetan Tea

The phenolic components, antioxidation, and anticancer effects of different polar parts of ethanol extract of Jinhua Tibetan tea were studied. Three polar fractions, i.e., ethyl acetate, n-butyl alcohol, and water fractions, of ethanol extract of Jinhua Tibetan tea were obtained via liquid-liquid extraction process. The contents of total polyphenols and total flavonoids of the three fractions and ethanol extract were determined using Folin-Ciocalteu and aluminum chloride-potassium acetate method, respectively. The contents of tea polyphenol monomers in all the parts were determined using high-performance liquid chromatography (HPLC) method. Their antioxidant activities of all the parts were tested and compared using DPPH radical scavenging, ABTS⁺ radical scavenging, and Fe²⁺ ion chelating methods. Their anti-proliferation effects on human cervical cancer HeLa cell were evaluated using cell counting Kit8. Results indicated that ethyl acetate fraction had the highest contents of total polyphenols and total flavonoids, as 384.65 mg/g and 188.82 mg/g, respectively, including gallic acid (GA), gallocatechin (GC), and epigallocatechin (EGC) as major phenolic monomers. Antioxidant activity test showed that compared with vitamin E, the DPPH and ABTS⁺ radical scavenging capacity of all the parts were as the sequence vitamin E>ethyl acetate fraction>n-butyl alcohol fraction>ethanol extract>water fraction, with P<0.05. When compared with EDTA, all parts possessed some Fe²⁺ ion chelating capacity, being EDTA (IC₅₀=48.3 µg/mL)>ethyl acetate fraction (332.4 µg/mL)>n-butyl alcohol fraction (1332.0 µg/mL)>ethanol extract (1846.0 µg/mL) and water fraction (1952.0 µg/mL), with P<0.05 between the parts, but there was not significant difference between water fraction and ethanol extract with the P>0.05. All the results indicated that the general antioxidant ability sequence was ethyl acetate fraction>n-butyl alcohol fraction>ethanol extract>water fraction. All the parts showed anti-proliferation activity to human cervical cancer HeLa cell, and all with dose-effect relationship. Ethyl acetate fraction showed the strongest anti-proliferation activity (IC₅₀ 111.6 µg/mL) to the HeLa cell. In conclusion, ethyl acetate fraction possessed the strongest capacity of both antioxidation and anti-proliferation to HeLa cell, resulted from its highest contents of polyphenols and flavonoids. The studies provide some preliminary scientific evidence of the antioxidant and anticancer effects of Jinhua Tibetan tea.