Performance Liquid Chromatographic Determination Of Flavonols In Tea

It is well known that tea has many beneficial effects to consumers' health, and the possible reason may be existence of many antioxidatives in tea, such as catechins (mainly flavanols) and flavonols. There are many reports about catechins in tea, but much less about flavonols. And teas from different geographic regions or of different classes could have much difference in flavonol contents. China, as a big tea exporter, produces varieties of teas in many regions. In this article, flavonol content in about 40 teas from 12 provinces of China were determinated and compared, and the possible reasons were given. Kaempferol was the main flavonol in green teas, and myricetin in total flavonol content didn't exceed 20%, even none, except in oolong teas. Sunlight hours and cultivars played an important role in flavonol content in green tea. But in fermentation teas, i.e., yellow, black, pu-er, and oolong tea, producing process was decisive. We also believed that there was a compound having much to do with myricetin, which leaded to the high content of myricetin in oolong tea.At the same time, chromatographic conditions and flavonol hydrolysis conditions were further optimized as well. We separated three flavonols successfully by adding 2% THF in eluant, thus making the determination of flavonols in teas by HPLC possible. Because the pretreatment of tea samples played an important role in the proper determination of flavonols, we paid much work on the hydrolysis of flavonols to gain optimum hydrolysis conditions of different classes of teas.