Purple tea (Camellia sinensis var. assamica) leaves as a potential functional ingredient: From extraction of phenolic compounds to cell-based antioxidant/biological activities

A statistical optimization study was used to maximize the extraction of bioactive compounds and antioxidant activity from green tea derived from purple leaves of Camellia sinensis var. assamica. Simultaneous optimization was applied, and a combination of 60 °C, 15 min, and a mass-solvent ratio of 1 g of dehydrated purple leaves to 62.3 mL of an ethanol/citric acid solution, were determined as the ideal extraction conditions. The optimized extract of purple tea leaves (OEPL) contained showed stability in relation to variations in pH, and lyophilized OEPL exerted cytotoxic and antiproliferative effects against cancerous cells (A549 and HCT8), demonstrated antimicrobial activity towards Listeria monocytogenes (ATCC 7644), Staphylococcus aureus (ATCC 13565) and Staphylococcus epidermidis (ATCC 12288), inhibition of α-amylase and α-glycosidase enzymes and reduced the release of pro-inflammatory cytokines (TNF-α, CXCL2/MIP-2, and IL-6) in lipopolysaccharides-stimulated RAW 264.7 macrophages. Thus, our results provide a broad assessment of the bioactivity of "green" extracts obtained by a simple and low-cost process using non-toxic solvents, and they have the potential to be used for technological applications.