Complete assignments of 1H and 13C NMR spectral data for three polyhydroxylated 12-ursen-type triterpenoids from Dischidia esquirolii

The complete assignments of all the (1)H and (13)C NMR signals of three polyhydroxylated 12-ursen-type triterpenes, 6beta,19alpha,22alpha-trihydroxyurs-12-en-3-oxo-28-oic acid (1), 3beta,6alpha,19alpha,23-tetrahydroxyurs-12-en-28- oic acid (2) and 3beta,6beta,19alpha,23-tetrahydroxyurs-12-en-28-oic acid (3), were carried out by means of homo- and hetero-nuclear two-dimensional NMR experiments. Compounds 1-3 were isolated from the aerial parts of Dischidia esquirolii. Of them, 1 and 2 were identified as new polyhydroxylated ursolic acid derivatives. Compound 2 is the C-6 hydroxyl epimer of 3, which was isolated first from Adina rubella, and its structure is revised in this paper.