Eight previously undescribed diterpenoids, caesamins A-H (1-8), were separated and identified from the seeds of Caesalpinia minax Hance. Their structures were characterized by extensive spectroscopic data and X-ray crystallographic analysis. Structurally, caesamin A (1) is the first cassane-type diterpenoid with a C23 carbon skeleton containing an unusual isopropyl. Caesamin F (6) represents the first example of cleistanthane diterpenoid from the genus Caesalpinia. Caesamins B (2) and F (6) exhibited inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages with IC50 values of 45.67 ± 0.92 and 42.99 ± 0.24 μM, comparable to positive control 43.69 ± 2.62 μM of NG-Monomethyl-L-arginine. Furthermore, the chemotaxonomic significance of the isolates was discussed.

BACKGROUND: Seeds of Caesalpinia minax Hance called \'Ku-Shi-Lian\' (KSL) in China have been used as Zhuang or Dai folk medicines for treatment of common cold, fever, rheumatoid arthritis and dysentery for hundred years.
OBJECTIVE: This study aimed to investigate therapeutic efficacy of KSL extract using complete Freund\'s adjuvant (CFA) induced arthritis in a rat model and the anti-inflammatory activity of cassane diterpenes as the main active material basis of this herb.
METHODS: Arthritis was induced in male Wistar rats (200-220 g) by immunization with CFA. Dexamethasone (DXMS) and Tripterygium glycosides (TG) were chosen as the positive drugs. Water soluble fraction (CMW, 1000 and 2000 mg/kg) and chloroform soluble fraction (CMC, 400 and 800 mg/kg) of KSL were orally administered from day 1 and continued for 21 days. Change of paw swelling perimeter, arthritics score, body weight growth, were observed, and the production of TNF-α, IL-1β and IL-6 in serum were measured by enzyme-linked immunosorbent assay (ELISA). The histological changes in the ankle joint were analyzed in adjuvant induced arthritis rats. Moreover, the inhibitory effect on mRNA expression of proinflammatory cytokine IL-1β, IL-6 and TNF-α of fourteen cassane diterpenes obtained from CMC extract were valued using the RAW 264.7 macrophages cell stimulated by lipopolysaccharide (LPS) assay.
RESULTS: The chloroform soluble fraction (CMC) showed the significantly suppressed change of paw swelling perimeter, arthritics score and increased body weight loss. The overproduction of TNF-α, IL-1β and IL-6 were remarkably suppressed in the serum. Fourteen cassane derivatives as the main constituents of CMC extract showed the promising activity on the expression mRNA of cytokine IL-1β, IL-6 and TNF-α produced by macrophages cells.
CONCLUSIONS: In this study, the chloroform soluble fraction of \'KSL\' (seeds of C. minax) was found to exert an anti-RA activity significantly in vivo for the first time, which indicted this fraction might be used as a powerful therapeutic agent for arthritis treatments. Cassane diterpenes, as the main constituents in this fraction, showed the anti-inflammation activity through the regulation of cytokine expression, which might be developed as target-agents for this national herb further developing.

Cassane diterpenoids were successfully and simultaneously identified in Caesalpinia minax Hance by high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. A total of 59 peaks were detected, and among them 51 compounds, including 41 furanocassane diterpenoids, 10 furanolactone cassane diterpenoids were simultaneously identified and characterized on the basis of the protonated molecule, retention behavior, and fragments in MS(2) . Ten compounds, including seven novel compounds, were identified or tentatively identified for the first time in C. minax. In a positive ion mode, the fragmentation pathways of cassane diterpenoids were also analyzed for the first time. The relative amounts of the five main diterpenoids (caesalpinin L, caesalpinin F2 , bondcellpin C, caesalpinin E, and ξ-caesalmin) were simultaneously quantified by high-performance liquid chromatography. Results showed that the newly discovered and known components of C. minax can be used to determine the material basis of bioactivity; this method can also be applied to analyze cassane diterpenoids in herbal medicines from the genus Caesalpinia belonging to the family Fabaceae.

Cassane skeletons are rare in nature, but often possess valuable medicinal properties. A furanoditerpenoid with an unusual A-seco-rearranged cassane skeleton, neocaesalminin A, and five furanoditerpenoids were isolated from seeds of Caesalpinia minax Hance, along with six known cassane derivatives, 7-O-acetyl-bonducellpin C, caesalmin F, caesalmin C, ζ-caesalmin, caesalmin E1 and caesalpinin K. Compound structures were determined by spectroscopy (HR-ESI-MS, UV, IR, 1D NMR, 2D NMR), X-ray crystallography and quantum chemical computation of electronic circular dichroism). Three of the previously known compounds exhibited significant inhibition of nitric oxide production of RAW264.7 macrophages stimulated by lipopolysaccharide (LPS).

An unprecedented trinorcassane diterpenoid and a cassane furanoditerpenoid were isolated from the seeds of Caesalpinia minax. It is the first example of dicylic cassane-type trinorditerpenoid, which is different from reported 16- or 17-norcassane diterpenoids. The structure of the compounds was elucidated on the basis of 1D and 2D NMR analysis. Biosynthesis pathways are postulated, and this pathway was supported by semi-synthesis.

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.