Tannins of aceraceous plants. Part II. Gallotannins having a 1,5-anhydro-D-glucitol core and some ellagitannins from Acer species.

Abstract

Tannins of two Acer species were investigated. Basides acertannin (1), gallotannins 2 and 3, having three and four galloyl groups on their 1, 5-anhydro-D-glucitol cores, were obtained from the leaves of Acer ginnala. The estimation of their tanning activity by the RMBG (relative affinity to methylene blue based on the affinity of geraniin) determination method revealed that the tanning activities of 2 and 3 are high, while that of 1, which has only two galloyl groups, is low. Two isomers (2a and 2b) of 2, and three isomers (3a, 3b and 3c) of 3 were respectively separated from each other after methylation. Their structures, in which all of the acyl groups (galloyl group, digalloyl group and/or trigalloyl group) are linked exclusively to O-2 and O-6 of the 1, 5-anhydro-D-glucitol core, were assigned. Fractionation of the constituents of leaves of Acer saccharum afforded two ellagitannins, geranin (10) and davidiin (11), and also chlorogenic acid and quercitrin.