Two new cassane diterpenoids from the seed kernels of Caesalpinia sinensis

Two new cassane diterpenoids, sucupiranin MN (1) and sucupiranin ML (2), together with two known compounds sucutinirane C (3) and deacetylsucutinirane C (4) were isolated from the seed kernels of Caesalpinia sinensis. Their structures were elucidated by means of analysis of comprehensive spectroscopic data, especially HRESIMS and 1D/2D NMR spectroscopy. Compounds 1-4 are typical furan-type cassane derivatives with an aromatized C ring. Biological evaluation revealed that compounds 1-4 at the concentration of 10 μM could inhibit the overproduction of NO in LPS-stimulated RAW 264.7 macrophages.

Synthesis of Tricyclic Pterolobirin H Analogue: Evaluation of Anticancer and Anti-Inflammatory Activities and Molecular Docking Investigations

Pterolobirin H (3), a cassane diterpene isolated from the roots of Pterolobium macropterum, exhibits important anti-inflammatory and anticancer properties. However, its relatively complex tetracyclic structure makes it difficult to obtain by chemical synthesis, thus limiting the studies of its biological activities. Therefore, we present here a short route to obtain a rational simplification of pterolobirin H (3) and some intermediates. The anti-inflammatory activity of these compounds was assayed in LPS-stimulated RAW 264.7 macrophages. All compounds showed potent inhibition of NO production, with percentages between 54 to 100% at sub-cytotoxic concentrations. The highest anti-inflammatory effect was shown for compounds 15 and 16. The simplified analog 16 revealed potential NO inhibition properties, being 2.34 higher than that of natural cassane pterolobirin H (3). On the other hand, hydroxyphenol 15 was also demonstrated to be the strongest NO inhibitor in RAW 264.7 macrophages (IC50 NO = 0.62 ± 0.21 μg/mL), with an IC50NO value 28.3 times lower than that of pterolobirin H (3). Moreover, the anticancer potential of these compounds was evaluated in three cancer cell lines: HT29 colon cancer cells, Hep-G2 hepatoma cells, and B16-F10 murine melanoma cells. Intermediate 15 was the most active against all the selected tumor cell lines. Compound 15 revealed the highest cytotoxic effect with the lowest IC50 value (IC50 = 2.45 ± 0.29 μg/mL in HT29 cells) and displayed an important apoptotic effect through an extrinsic pathway, as evidenced in the flow cytometry analysis. Furthermore, the Hoechst staining assay showed that analog 15 triggered morphological changes, including nuclear fragmentation and chromatin condensation, in treated HT29 cells. Finally, the in silico studies demonstrated that cassane analogs exhibit promising binding affinities and docking performance with iNOS and caspase 8, which confirms the obtained experimental results.

Discovery of diversified cassane diterpenoids as potent antibacterial agents from Caesaplinia pulcherrima and their mechanisms

BACKGROUND

Natural products play a significant role in the development of novel bactericide candidates. Caesalpinia pulcherrima, a traditional medicine, had anti-inflammatory, antimicrobial, and antifeedant activities, therefore the previous bioassay results of C. pulcherrima implied that its main active ingredients may have potential to be used as botanical bactericides.

RESULTS

Bio-guided isolation of C. pulcherrima was conducted to obtain 11 novel cassane diterpenoids (capulchemins A-K) and 10 known sesquiterpenes. Their structures were established by extensive spectroscopic methods and single-crystal X-ray diffraction analyses. Capulchemins A-F possess a rare aromatic C ring, while capulchemin K with a 15,16-degradative carbon skeleton represents a rare group of cassane diterpenes. Capulchemin A exhibited remarkable antibacterial activity against four phytopathogenic bacteria, particularly against Pseudomonas syringae pv. actinidae and Bacillus cereus, with minimal inhibitory concentration values of 3.13 μM. Meanwhile, capulchemin A showed significant control effect on kiwifruit canker in vivo. Further investigation of its mechanism of antibacterial activity revealed that compound 1 was closely related to destroy cell membrane to cause cell death. Additionally, some of those cassane diterpenoids showed potential antifeedant against Mythimna separate walker and Plutella xylostella. Consequently, capulchemin A could have the potential to be used as a template for the development for new eco-friendly NP-based bactericides.

CONCLUSION

These data contribute to a better understanding of the antibacterial activity of cassane diterpenes. Cassane diterpenes have been discovered to be leading to broad application prospects in the development as novel botanical bactericides. © 2023 Society of Chemical Industry.

Antibacterial Activity of Two New Cassane Diterpenoids from Caesaplinia pulcherrima against Bacillus cereus by Damage to Cell Membrane

Bacillus cereus, a Gram-positive bacterium, is a food contaminant that threatens the health of thousands of people around the world. Because of the continuous emergence of drug-resistant strains, the development of new classes of bactericides from natural products is of high priority. In this study, two novel cassane diterpenoids (pulchins A and B) and three known ones (3-5) were elucidated from the medicinal plant Caesaplinia pulcherrima (L.) Sw. Pulchin A, with a rare "6/6/6/3" carbon skeleton, showed significant antibacterial activity against B. cereus and Staphylococcus aureus, with MIC values of 3.13 and 6.25 μM, respectively. Further investigation of its mechanism of antibacterial activity against B. cereus is also discussed in detail. The results revealed that the antibacterial activity of pulchin A against B. cereus may be caused by pulchin A interfering with bacterial cell membrane proteins, affecting membrane permeability and causing cell damage or death. Thus, pulchin A may have a potential application as an antibacterial agent in the food and agricultural industries.

Three new cassane-type diterpenoids from Caesalpinia sinensis

Three new cassane-type diterpenoids, namely, (4S)-6β,12α,19-trihydroxy-cass-13(15)-en-16,12-olide (1), cass-13(15)-en-​16,12-olide (2), and 12α-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 IC₅₀ value of 217.45 ± 36.4 μM.

Isolation and structure elucidation of two new cassane derivatives from the seed kernels of Caesalpinia sinensis

Two new cassane-type derivatives (1-2), together with three known compounds (3-5), were isolated from the seed kernels of Caesalpinia sinensis. Their structures were elucidated on the basis of interpretation of comprehensive spectroscopic data, including HRESIMS and 1D/2D NMR spectroscopy, and the absolute configuration were established by means of ECD calculation. Compound 2, possessing a 16-degradative cassane skeleton, was rarely encountered in cassane diterpenoids isolated from the genus Caesalpinia. All compounds were evaluated for their anti-inflammatory activities against the overproduction of NO in LPS-stimulated RAW 264.7 macrophages, and compounds 1-5 could inhibit production of NO at the concentration of 50 μM.

Synthesis and Biological Evaluation of Cassane Diterpene (5α)-Vuacapane-8(14), 9(11)-Diene and of Some Related Compounds

A set of thirteen cassane-type diterpenes was synthesized and an expedient synthetic route was used to evaluate 14-desmethyl analogs of the most active tested cassane. The anti-inflammatory activities of these 13 compounds were evaluated on a lipopolysaccharide (LPS)-activated RAW 264.7 cell line by inhibition of nitric oxide (NO) production, some of them reaching 100% NO inhibition after 72 h of treatment. The greatest anti-inflammatory effect was observed for compounds 16 and 20 with an IC_{50 NO} of 2.98 ± 0.04 μg/mL and 5.71 ± 0.14 μg/mL, respectively. Flow-cytometry analysis was used to determine the cell cycle distribution and showed that the inhibition in NO release was accompanied by a reversion of the differentiation processes. Moreover, the anti-cancer potential of these 13 compounds were evaluated in three tumor cell lines (B16-F10, HT29, and Hep G2). The strongest cytotoxic effect was achieved by salicylaldehyde 20, and pterolobirin G (6), with IC₅₀ values around 3 μg/mL in HT29 cells, with total apoptosis rates 80% at IC₈₀ concentrations, producing a significant cell-cycle arrest in the G0/G1 phase, and a possible activation of the extrinsic apoptotic pathway. Additionally, initial SAR data analysis showed that the methyl group at the C-14 positions of cassane diterpenoids is not always important for their cytotoxic and anti-inflammatory activities.

Four new cassane-type diterpenoids from the seed kernels of Caesalpinia cucullata Roxb

The first investigation of chemical composition in seed kernels of Caesalpinia cucullata Roxb. resulted in the separation of four new cassane diterpenes, including three furanoditerpenes (1, 2 and 4) and one tricyclic type (3). It was the first found cassane diterpenoids from this plant. Their gross structures were elucidated by means of comprehensive spectroscopic analysis (UV, IR, NMR, HRESIMS) as well as electronic circular dichroism (ECD) calculation. The compound 1 possess a rare isomerized dihydrofuran ring in structure framework. In bioassay, compounds 1-4 exhibited moderate anti-inflammatory activity by inhibiting production of NO in LPS-induced RAW 264.7 cells.

Two new cassane-type diterpenoids from the seed kernels of Caesalpinia bonduc (Linn.) Roxb. and their anti-inflammatory activity

In this study, phytochemical investigation on the chloroform soluble fraction of seed kernels of Caesalpinia bonduc led to the isolation of two new cassane-type diterpenoids, norcaesalpinin Q (1) and caesalpinin MR (2), together with seven known compounds (3-9). The structures of the new compounds were elucidated on the basis of extensive NMR spectroscopic and mass spectrometric analyses, and their absolute configurations were determined by electronic circular dichroism (ECD) calculations. All compounds were evaluated for inhibitory effects against NO production of RAW264.7 cells induced by LPS, and compounds 5, 7 and 8 could inhibited the production of NO at the concentration of 50 µM.

Anti-proliferative cassane-type diterpenoids from the seeds of Caesalpinia minax

The seeds of Caesalpinia minax Hance have shown anti-tumor potential, while the chemical principle is still unknown. In a search for anti-tumor compounds, six new cassane-type diterpenoids, 12-demethylcaesalpin G (1), caesalpinolide H (2), 12-demethylcaesalpin H (3), caesalpinolide J (4), 12-O-ethyl neocaesalpin B (5), and 3-deacetyldecapetpene B (6), were isolated from the seeds of C. minax Hance, along with fifteen known analogues. The structures of the new compounds were established by means of spectroscopic techniques (NMR, HRESIMS and IR). The absolute configurations of the new compounds were determined by their ECD spectra. All of the new compounds were tested for their anti-proliferative activity against human lung cancer A549 cells, breast cancer MCF-7 cells, and ovarian cancer HEY cells. The results indicated that only compound 6 displayed moderate cytotoxicity against three cancer cell lines. Thus, the opening of furan ring in cassane-type diterpenoids might enhance the cytotoxic activity.

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.

et Perr.) Brenan (Fabaceae)

During our research to contribute to the elucidation of the chemical composition of the root bark of E. suaveolens, six non-nitrogenous cassane diterpenoids (1-6) were isolated and identified. Of these secondary metabolites, three have never been previously described: Cassan-13,15-dien-3-oxo-17-oic acid (2), Cassan-15-en-[7,17]-γ-lactone (3) and 6α-hydroxy-cassamic acid (5). The other are known but, never isolated from the root barks of E. suaveolens (Fabaceae): Cassan-13,15-dien-17-oic acid (1), 6α-hydroxy-cassamic acid methyl esther (4) and cassamic acid (6). Their structures were established according to the spectroscopic data (NMR 1D and 2D, HR-ESI-MS and IR), in comparison with those of literature. The originality of this study lies in the fact that three new natural molecules were isolated and identified. In addition, all the isolated compounds (1-6) were reported for the first time from the root barks of E. suaveolens.

Pharmacokinetic and tissue distribution studies of cassane diterpenoids, in rats through an ultra-high-performance liquid chromatography-Q exactive hybrid quadrupole-Orbitrap high-resolution accurate mass spectrometry

Cassane diterpenoids (CA) are considered as the main active constituents of medicinal plants belonging to the Caesalpinia genus. Three cassane derivatives, bonducellpin G (BG), 7-O-acetyl-bonducellpin C (7-O-AC) and caesalmin E (CE), isolated from Caesalpinia minax Hance seeds, showed strong anti-inflammatory activity. In this paper, pharmacokinetics (BG, 7-O-AC, CE) and tissue distribution (7-O-AC, CE) properties were studied for the first time using a reliable, sensitive and rapid UHPLC-Q-Orbitrap HR-MS to develop new anti-inflammatory agents. A novel quantitative method with full scan in positive ion mode was used to determine the contents of compounds. They were separated using acetonitrile-water (0.1% formic acid) as gradient mobile phase. The calibration curve displayed good linearity and the lower limit of quantitation was 0.005-0.02 μg/mL for all analytes. Meanwhile, the absorption, distribution, metabolism, excretion (ADME) property was predicted using PreADMET web. The pharmacokinetic parameters indicated that they were absorbed quickly, eliminated rapidly together with high blood concentration. The results of tissue distribution demonstrated that CE was distributed rapidly and widely among tissues, and stomach was the main tissue site of CE and 7-O-AC, followed by small intestine/liver. This study indicates that the structures and dosages of active CA should be modified to help improve the absorption rate and residence time, and the findings are helpful for the pharmaceutical design of CA derivatives.

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.