Definitive evidence of the presence of 24-methylenecycloartanyl ferulate and 24-methylenecycloartanyl caffeate in barley

Abstract

γ-Oryzanol (OZ), which has a lot of beneficial effects, is a mixture of ferulic acid esters of triterpene alcohols (i.e., triterpene alcohol type of OZ (TTA-OZ)) and ferulic acid esters of plant sterols (i.e., plant sterol type of OZ (PS-OZ)). Although it has been reported that OZ is found in several kinds of cereal typified by rice, TTA-OZ (e.g., 24-methylenecycloartanyl ferulate (24MCA-FA)) has been believed to be characteristic to rice and has not been found in other cereals. In this study, we isolated a compound considered as a TTA-OZ (i.e., 24MCA-FA) from barley and determined the chemical structure using by HPLC-UV-MS, high-resolution MS, and NMR. Based on these results, we proved for the first time that barley certainly contains 24MCA-FA (i.e., TTA-OZ). During the isolation and purification of 24MCA-FA from barley, we found the prospect that a compound with similar properties to OZ (compound-X) might exist. To confirm this finding, the compound-X was also isolated, determined the chemical structure, and identified as a caffeic acid ester of 24-methylenecycloartanol (24MCA-CA), which has rarely been reported before. We also quantified these compounds in various species of barley cultivars and found for the first time the existence of 24MCA-FA and 24MCA-CA in various barley. Through these findings, it opens the possibility to use barley as a new source of 24MCA-FA and 24MCA-CA.