Phenolic compounds, antioxidant capacity, and in vitro-amylase inhibitory potential of tea infusions (Camellia sinensis) commercialized in Chile

Chile is considered the largest tea consumer in America, so a broad variety of tea types and brands are available in Chilean markets. Thirty-four commercial teas (white, green, red, oolong, and black) commonly found in Chile were evaluated according to their phenolic profiles, antioxidant capacity, and in vitro inhibition against alpha-amylase relevant for hyperglycemia control. Multivariate tools were used to evidence patterns among samples respect their biochemical parameters. Green and white tea groups showed higher total phenolic contents than red and black teas. All tea samples inhibited the 2,2-diphenyl-1-picrylhydrazyl free radical and black teas significantly inhibited the alpha-amylase enzyme. Major phenolics detected by liquid chromatography in green and white teas were epigallocatechingallate and epicatechingallate, whereas gallic acid was common in black, red, and oolong teas. Caffeine was found across all samples. The multivariate analysis evidenced a high variability among analyzed tea and even from brand to brand.