Quantitative Determination of the Triterpenoids and Total Tannin in Korean Rubus species by HPLC

The triterpenoids contained in four Rubus species (Rosaceae) were quantitatively analyzed using HPLC to select plants with large quantities of niga-ichigoside $F_1$. Unripe fruits, ripe fruits, and leaves were extracted to estimate the quantity of niga-ichigoside $F_1$, together with Rubus-specific $19{\alpha}$-hydroxyursane-type triterpenoids, euscaphic acid, tormentic acid, and kaji-ichigoside $F_1$, and a dimeric triterpenoid coreanoside $F_1$. Niga-ichigoside $F_1$ was most abundant in the leaves of R. crataegifolius (23.4 mg/g dry weight). The amount of triterpenoid in the black, ripe fruits of R. coreanus was lower than the unripe fruits of the same plant. On the other hand, the ripe fruits of three plants, R. crataegifolius, R. parvifolius and R. pungens var. oldhami, which are reddish, contained higher or similar level of triterpenoids than their unripe fruits. In addition, the concentration of niga-ichigoside $F_1$ in the ripe fruit of R. crataegifolius was 20.5 mg/g, suggesting that the fruits could be used as a functional food. Methyl gallate and ellagic acid were used as quantitative indices of total tannin. Methyl gallate levels were higher in ripe fruits than unripe fruits in R. crataegifolius, R. pungens var. oldhami, and R. parvifolius. In R. crataegifolius, the quantity of methyl gallate was 30.5 mg/g in ripe fruit, but 1.19 mg/g in unripe fruit.