Identification of two teaghrelins in Shy‐jih‐chuen oolong tea

Teaghrelins are unique acylated flavonoid tetraglycosides originally identified in Chin‐shin oolong tea, and proposed to be potential oral analogs of ghrelin. Two acylated flavonoid tetraglycosides were isolated from Shy‐jih‐chuen oolong tea, and their chemical structures were determined to be quercetin and kaempferol 3‐O‐[α‐L‐arabinopyranosyl(1 → 3)][2ʺ‐O‐(E)‐p‐coumaroyl] [β‐D‐glucopyranosyl(1 → 3)‐α‐L‐rhamnopyranosyl(1 → 6)]‐β‐D‐glucoside. These two compounds were extremely similar to the two teaghrelins (teaghrelin‐1 and teaghrelin‐2) in Chin‐shin oolong tea by simply replacing a glucopyranosyl group with an arabinopyranosyl group. Molecular modeling showed that the two putative teaghrelins identified in Shy‐jih‐chuen docked to and interacted with the ghrelin receptor as well as teaghrelin‐1 and teaghrelin‐2. Mixture of these two putative teaghrelins was shown to enhance the release of growth hormone from primary anterior pituitary cells of rats. The results suggest that two teaghrelins, named teaghrelin‐3 and teaghrelin‐4, are present in Shy‐jih‐chuen oolong tea and possess biological activities analogous to teaghrelins in Chin‐shin oolong tea. Practical applications According to this study, teaghrelin‐3 and teaghrelin‐4 may be regarded as active ingredients for the quality control of Shy‐jih‐chuen oolong tea. The content of teaghrelins may serve as a key factor for the farmers to select new tea plants in their next propagation of Shy‐jih‐chuen cultivar. Crude water extract of Shy‐jih‐chuen oolong tea containing teaghrelins is considered to be an adequate food supplement or additive in functional food products. In Shy‐jih‐chuen oolong tea, two acylated flavonoid tetraglycosides, named teaghrelin‐3 and teaghrelin‐4, were identified and demonstrated to be ghrelin analogs. Teaghrelin‐3 and teaghrelin‐4 as well as teaghrelin‐1 and teaghrelin‐2 from Chin‐shin oolong tea were shown to possess comparable strength of interaction with the ghrelin receptor.