Anthocyanins enriched purple tea exhibits antioxidant, immunostimulatory and anticancer activities

Purple coloured tea shoot clones have gained interest due to high content of anthocyanins in addition to catechins. Transcript expression of genes encoding anthocyanidin reductase (ANR), dihydroflavonol-4-reductase (DFR), anthocyanidin synthase (ANS), flavonol synthase (FLS) and leucoantho cyanidin reductase (LAR) enzymes in three new purple shoot tea clones compared with normal tea clone showed higher expression of CsDFR, CsANR, CsANS and lower expression of CsFLS and CsLAR in purple shoot clones compared to normal clone. Expression pattern supported high content of anthocyanins in purple tea. Four anthocyanins (AN_1-4) were isolated and characterized by UPLC-ESI-QToF-MS/MS from IHBT 269 clone which recorded highest total anthocyanins content. Cyanidin-3-O-β-d-(6-(E)-coumaroyl) glucopyranoside (AN₂) showed highest in vitro antioxidant activity (IC_50 DPPH = 25.27 ± 0.02 μg/mL and IC_50 ABTS = 10.71 ± 0.01 μg/mL). Anticancer and immunostimulatory activities of cyanidin-3-glucoside (AN₁), cyanidin-3-O-β-d-(6-(E)-coumaroyl) glucopyranoside (AN₂), delphinidin-3-O-β-d-(6-(E)-coumaroyl) glucopyranoside (AN₃), cyanidin-3-O-(2-O-β-xylopyranosyl-6-O-acetyl)-β-glucopyranoside (AN₄) and crude anthocyanin extract (AN₅) showed high therapeutic perspective. Anthocyanins AN_1-4 and crude extract AN₅ showed cytotoxicity on C-6 cancer cells and high relative fluorescence units (RFU) at 200 μg/mL suggesting promising apoptosis induction activity as well as influential immunostimulatory potential. Observations demonstrate potential of purple anthocyanins enriched tea clone for exploitation as a nutraceutical product.