Three new cassane-type diterpenoids from Caesalpinia sinensis .

Three new cassane-type diterpenoids, namely, (4 S )-6 β ,12 α ,19-trihydroxy-cass-13(15)-en-16,12-olide ( 1 ), cass-13(15)-en-​16,12-olide ( 2 ), and 12 α -hydroxy-cass-13(15)-en-16,12-olide ( 3 ), were isolated from the seeds of Caesalpinia sinensis. The structures of 1 - 3 were established by extensive spectroscopic analysis, and their absolute configurations were assigned by electronic circular dichroism (ECD) calculations. The inhibitory activities against PTP1B of the isolated compounds were evaluated. The results showed that compound 2 possessed PTP1B inhibitory activity with an IC ₅₀ value of 217.45 ± 36.4 μM.