METHODS AND RESULTS:
The constituents of the MeOH extract of Salvia miltiorhiza BUNGE, which showed strong aldose reductase (AR) inhibitory activity, were examined, and two new abietane-type diterpenoids, danshenol A (1) and Danshenol B (2), were isolated together with six known ones: dihydrotanshimme I (3), cryptotanshinone (4), tanshinone I (5), tanshinone IIA (6), (-)-danshexinkun A (7), and sugiol (8). Among them, 4, 5, and 8 were weak AR inhibitors with IC50 from 4.80 to > 10.0 microM, while 1, 2, 3, 6, and 7 were strong inhibitors (IC50 from 0.10 to 1.75 microM).
Danshenol A (1), the strongest inhibitor, had IC50 of 0.10 microM which is comparable to that of epalrestat in clinical use. Moreover, from a consideration of IC50, and yield of each compound, it was concluded that tanshinone IIA (6) is the major active constituent of the MeOH extract and danshenol A (I) and (-)danshexinkun A(7) are the minor ones.