Anti-pancreatic cancer activity of cassane diterpenoids isolated from the seeds of Caesalpinia sappan mediated by autophagy activation via ROS/AMPK/mTORC1 pathway

Three undescribed cassane diterpenoids, caesalpanins D-F (1-3), and seven known ones were isolated from the seeds of Caesalpinia sappan. Structures and absolute configurations of 1-3 were elucidated based on the extensive spectroscopic analysis, single-crystal X-ray diffraction analysis, and ECD calculations. Structurally, compound 1 was the first example of 18-norcassane diterpenoid and 2 was a rare 20-norcassane diterpenoid having an unusual five-membered oxygen bridge between C-10/C-18. The anti-proliferative activity of 1, 3, and 4-10 against PANC-1 cells (pancreatic ductal adenocarcinoma cell line) was evaluated, and phanginin H (4) was found to exhibit anti-cancer activity with IC50 value of 18.13 ± 0.63 μM. Compound 4 inhibited PANC-1 cell growth by arresting the cell cycle at G2/M phase via regulation of cyclin-dependent kinases, and the self-renewal and metastasis of PANC-1 cells by suppressing cancer cell stemness. Furthermore, compound 4 induced ROS generation and subsequently activated autophagy, which was demonstrated by the formation of autophagic vacuoles and dynamic change of autophagic flux. The induced ROS accumulation resulted in AMPK activation and subsequently regulation of mTORC1 activity and ULK phosphorylation, indicating that 4 triggered autophagy through ROS/AMPK/mTORC1 pathway. These findings suggested that 4 might potentially be an autophagy inducer for the therapy of pancreatic cancer.

Synthesis of Neocaesalpin A, AA, and Nominal Neocaesalpin K

The first total synthesis of heavily oxidized cassane-type diterpenoid neocaesalpin A (1) is disclosed. At the heart of the synthesis lies an intermolecular Diels-Alder reaction that rapidly assembles the target framework from commercial materials. A carefully orchestrated sequence of oxidations secured the desired oxygenation pattern. Late-stage release of the characteristic butenolide occurred through a novel mercury(II)-mediated furan oxidation. Successful extension of the route allowed preparation of neocaesalpin AA (2) as well as nominal neocaesalpin K (3) and suggested structural revision of neocaesalpin K, leading to the hypothesis that the two are likely the same natural product with correct assignment as 2.

Two new cassane-type diterpenoids from the seeds of Caesalpinia sappan

A new cassane diterpenoid, caesappine A (1), and a new natural cassane diterpenoid, caesappine B (2) were isolated from the seeds of Caesalpinia sappan. The new structures of compounds 1 and 2 were elucidated by analysing their 1D NMR, 2D NMR and HR-ESI-MS spectra. Compounds 1 and 2 were evaluated for the cytotoxic activities on Hela and HepG-2 human cancer cell lines.

Three new ester glycosides with cytotoxic activity from the seeds of Caesalpinia sappan

Three new ester glycosides, named as Caesateroside A (1), Caesateroside B (2) and Caesateroside C (3) were obtained from the seeds of Caesalpinia sappan. The new structures of compounds 1-3 were elucidated by analyzing their 1 D NMR, 2 D NMR and HR-ESI-MS spectra. Compounds 1-3 showed weak-moderate cytotoxicity against Hela and HepG-2 human cancer cell lines.

Cytotoxic and Pro-Apoptotic Effects of Cassane Diterpenoids from the Seeds of Caesalpinia sappan in Cancer Cells

The chemical study on the seeds of Caesalpinia sappan led to the isolation of five new cassane diterpenoids, phanginins R‒T (1–3) and caesalsappanins M and N (4 and 5), together with seven known compounds 6–12. Their structures were elucidated on the basis of NMR and HRESIMS analyses. The absolute configurations of compounds 1 and 4 were determined by the corresponding CD spectra. All the isolated compounds were tested for their cytotoxicity against ovarian cancer A2780 and HEY, gastric cancer AGS, and non-small cell lung cancer A549 cells. Compound 1 displayed significant toxicity against the four cell lines with the IC₅₀ values of 9.9 ± 1.6 µM, 12.2 ± 6.5 µM, 5.3 ± 1.9 µM, and 12.3 ± 3.1 µM, respectively. Compound 1 induced G1 phase cell cycle arrest in A2780 cells. Furthermore, compound 1 dose-dependently induced A2780 cells apoptosis as evidenced by Hoechst 33342 staining, Annexin V positive cells, the up-regulated cleaved-PARP and the enhanced Bax/Bcl-2 ratio. What’s more, compound 1 also promoted the expression of the tumor suppressor p53 protein. These findings indicate that cassane diterpenoids might have potential as anti-cancer agents, and further in vivo animal studies and structural modification investigation are needed.

Antimalarial and Antiproliferative Cassane Diterpenes of Caesalpinia sappan

Bioassay-guided fractionation of a methanol extract of the seeds of Caesalpinia sappan led to the isolation of 12 new cassane-type diterpenes, caesalsappanins A-L (1-12). Their structures were elucidated on the basis of NMR and HRESIMS analysis, and the absolute configuration of compound 1 was determined by single-crystal X-ray crystallography. All isolated compounds were tested against a chloroquine-resistant Plasmodium falciparum strain for antiplasmodial activities and against a small panel of human cancer cell lines for antiproliferative activities. Compounds 7 and 8 displayed antimalarial activity against the chloroquine-resistant K1 strain of P. falciparum with IC50 values of 0.78 and 0.52 μM and selectivity indices of 17.6 and 16.4, respectively. Compound 10 showed antiproliferative activity against the KB cancer cell line with an IC50 value of 7.4 μM.

Cytotoxic constituents from the seeds of Vietnamese Caesalpinia sappan

CONTEXT

Caesalpinia sappan Linn. (Leguminosae) has been used in folk medicines for the treatment of many diseases. The heartwood of this plant contains various phenolic components with interesting biological applications; however, the chemical and biological potentials of the seed of this plant have not been fully explored.

OBJECTIVE

This study identified the cytotoxic activity of compounds from the seeds of C. sappan.

MATERIALS AND METHODS

The methanol extract of the seed of C. sappan was suspended in H2O and then partitioned with CH2Cl2, EtOAc, and n-BuOH, successively. Diterpenoid compounds were isolated from the CH2Cl2-soluble fraction by silica gel column chromatography methods using organic solvents. The compound structures were determined by detailed analysis of NMR and MS spectral data. Cytotoxic activity was measured using a modified MTT assay against HL-60, HeLa, MCF-7, and LLC cancer cells. The activation of caspase-3 enzyme and western blotting assay were performed to confirm inhibitory mechanism of active compound.

RESULTS

Five cassane-type diterpenoids were isolated and identified as phanginin I (1), phaginin A (2), phanginin D (3), phanginin H (4), and phanginin J (5). Compounds 1-4 showed effective inhibition against HL-60 cells with the IC50 values of 16.4 ± 1.5, 19.2 ± 2.0, 11.7 ± 1.6, and 22.5 ± 5.1 μM. Compounds 1-3 exhibited cytotoxic activity against HeLa cells with the IC50 values of 28.1 ± 3.6, 37.2 ± 3.4, and 22.7 ± 2.8 μM. Treatment of HL-60 cell lines with various concentrations of 3 (0-30 μM) resulted in the growth inhibition and induction of apoptosis.

CONCLUSION

These findings demonstrate that compound 3 (phanginin D) is one of the main active components of the seed of C. sappan activating caspases-3 which contribute to apoptotic cell death.

Cassane-type diterpenoids from the seed kernels of Caesalpinia bonduc

Seven new cassane diterpenoids (1-7), along with three known compounds (8-10), were isolated from the seed kernels of Caesalpinia bonduc. The structures were elucidated by extensive 1D and 2D NMR (HSQC, HMBC and ROESY) and mass (HRESIMS) spectroscopic data analyses. The structure and absolute configuration of compound 1 were confirmed by a single-crystal X-ray diffraction experiment. All isolates were tested for their cytotoxicity against HepG-2, MCF-7 and MG-63 cells, and 8-10 showed weak inhibitory activities.