Characterization of Phenolics in the Flesh Tissue of 'Tsuyuakane', a Red Flesh Type of Japanese Apricot (Prunus mume Sieb. et Zucc.) and its Effect on Postprandial Blood Glucose Levels in Rats

The phenolic composition of fruit from the new cultivar of Japanese apricot (Prunus mume Sieb. et Zucc.), 'Tsuyuakane', was investigated. Comparison of phenolic contents among 'Tsuyuakane' and its parental cultivars suggested that the high level of anthocyanins in 'Tsuyuakane' is inherited from one of its parental varieties, 'Kasaharahatankyo', and its high level of chlorogenic acid derivatives is likely inherited from the other parental variety, 'Yousei-ume'. One of the characteristic phenolic compounds found in the fruit of 'Tsuyuakane' was neochlorogenic acid. Exogenous ethylene treatment of the fruit, which is known to increase the red color intensity of 'Tsuyuakane' fruit, increased not only anthocyanin levels but also neochlorogenic acid content. The existence of acetylated sucrose esters of hydroxycinnamates was suggested by LC-MS analysis. Moreover, the inhibitory effects of 'Tsuyuakane' phenolic compounds (TAP) on rat small intestinal disaccharidases and their suppressive effects on postprandial blood glucose levels in rats were evaluated. TAP inhibited maltase, glucoamylase, and sucrase in vitro. TAP delayed postprandial blood glucose level elevation when rats were fed with starch, however, no significant effect was observed upon administration with maltose or sucrose.