Occurrence of Glycosidically Conjugated 1-Phenylethanol and Its Hydrolase β-Primeverosidase in Tea (Camellia sinensis) Flowers

摘要

A previous study found that 1-phenylethanol (lPE) was a major endogenous volatile compound in tea (Camellia sinensis) flowers and can be transformed to glycosically conjugated 1PE (lPE-Gly). However, occurrences of IPE-Gly in plants remain unknown. In this study, four IPE-Glys have been isolated from tea flowers. Three of them were determined as (R)-1PE β-n-glucopyranoside ((R)-1PE-Glu), (S)-1PE-Glu, and (S)-1PEβ-primeveroside ((S)-IPE-Pri), respectively, on the basis of NMR, MS, LC-MS, and GC-MS evidence. The other one was identified as (R)-1PE-Pri on the basis of LC-MS and GC-MS data. Moreover, these IPE-Glys were chemically synthesized as the authentic standards to further confirm their occurrences in tea flowers. IPE-Glu had a higher molar concentration than IPE-Pri in each floral stage and organ. The ratio of (R) to (S) differed between IPE-Glu and IPE-Pri. In addition, a IPE-Gly hydrolase β-primeverosidase recombinant protein produced in Escherichia coli exhibited high hydrolysis activity toward (R)-IPE-Pri. However, β-primeverosidase transcript level was not highly expressed in the anther part, which accumulated the highest contents of IPE-Gly and 1PE. This suggests that IPE-Gly may not be easily hydrolyzed to liberate 1PE in tea flowers. This study provides evidence of occurrences of IPE-Glys in plants for the first time.