Novel synthesis of leucoside by enzymatic hydrolysis of tea seed extract.

The application of tea seed extract (TSE) has been widely investigated owing to its biological activities. In this paper, two flavonol triglycosides found in TSE, camelliaside A (CamA) and camelliaside B (CamB), were subjected to hydrolysis in the presence of three commercial enzyme complexes of the Pectinex® series, 5XL, XXL and Ultra SP-L (Ultra). XXL and 5XL induced stepwise deglycosylation of CamA and CamB to yield kaempferol diglycoside (nicotiflorin), kaempferol monoglycoside (astragalin) and kaempferol, while Ultra produced an additional new compound (1) that had not been observed in earlier studies. Upon hydrolysis of isolated CamA and CamB, compound (1) was obtained only from CamB. Both the molecular ion peak in liquid chromatography/mass spectrometry and the ¹H and ¹³C nuclear magnetic resonance spectra of (1) isolated by Ultra-induced hydrolysis of TSE indicated that (1) was kaempferol 3-O-β-xylopyranosyl (1 → 2)-β-glucopyranoside (leucoside), formed by selective hydrolysis of the rhamnosyl moiety of CamB. Pure leucoside can be prepared by enzymatic partial hydrolysis of TSE. This is the first study to address the synthesis of pure leucoside from a natural source.