Patuletin acetylrhamnosides from Kalanchoe brasiliensis as inhibitors of human lymphocyte proliferative activity.

The fractionation of the juice of fresh stems and leaves of Kalanchoe brasiliensis was monitored by an assay measuring lymphocyte proliferative activity and allowed the isolation and identification of seven patuletin rhamnoside derivatives [1-7]. Three of them are novel, namely, patuletin 3-O-(4"-O-acetyl-alpha-L-rhamnopyranosyl)-7-O-(2'"-O-acetyl- alpha-L-rhamnopyranoside) [1], patuletin 3-O-alpha-L-rhamnopyranosyl-7-O-(2'"-O-acetyl-alpha-L- rhamnopyranoside) [3], and patuletin 3-O-(4"-O-acetyl-alpha-L-rhamnopyranosyl)-7-O- rhamnopyranoside [4], and four are known [2, 5-7]. Their structures were determined by the analysis of 1H-1H and 1H-13C COSY nmr, ci, and fab mass spectra.