Seven new cassane furanoditerpenes from the seeds of Caesalpinia minax.

A bioassay-guided study led to the isolation of seven new cassane furanoditerpenes, designated as spirocaesalmin B (1), caesalpinin M1 (2), caesalpinin M2 (3), caesalmin E1 (4), caesalmin E2 (5), caesalmin E3 (6), caesalpinin F1 (7) and three known compounds neocaesalpin A(8), neocaesalpin L(9), neocaesalpin L1(10) from the seeds of Caesalpinia minax Hance. Compound structures were determined on the basis of extensive spectroscopic analyses, including X-ray crystallographic analysis, HRESI-MS, UV, IR, 1D and 2D NMR (HSQC, HMBC, NOESY) methods. Some absolute configurations were confirmed via the circular dichroism (CD) spectra. Compound 1 is the first example of an A-seco-rearranged cassane furanoditerpene with an unusual skeleton isolated from the genus Caesalpinia. All compound inhibitory effects on influenza virus neuraminidase (NA) in vitro were valued for the first time. Compared with the positive control (Zanamivir), new compounds were found to show moderate inhibitory activity.