Cassane Diterpenoids from the Pericarps of Caesalpinia bonduc

Caesalpinbondin A, a Novel Diterpenoid Lactone With an Unprecedented Carbon Skeleton from the Seeds of Caesalpinia bonduc

One novel diterpenoid lactone named caesalpinbondin A (1) that possesses an unprecedented tetracyclic ring system in which a 6/6/5-fused tricyclic ring and a 4,5-dimethyldihydrofuran-2(3H)-one were connected by a C-C single bond comprising a 5-(naphtho [2,3-b]furan-7-yl)dihydrofuran-2(3H)-one moiety was isolated from the seeds of Caesalpinia bonduc. Its chemical structure was established by extensive spectroscopic methods, and its absolute configuration was further determined by single-crystal X-ray diffraction analysis and electronic circular dichroism calculation. The biological evaluation suggested that compound 1 demonstrated potent anti-Alzheimer’s disease (AD) bioactivity, which could delay paralysis of transgenic AD Caenorhabditis elegans. A possible biogenetic pathway of 1 was also proposed.

Cassane-Type Diterpenoids from the Seeds of Caesalpinia bonduc (L.) Roxb

Ten new cassane-type diterpenoids were isolated from the seeds of Caesalpinia bonduc (L.) Roxb., including 6α-hydroxycaesalpinin P (1), 14-epi-caesalpinin E1 (2), 6-deacetylcaesalmin Z (3), 14-epi-caesalmin Z (4), caesalpinolides I (5), K (6), L (7), M (9) and N (10), and 14-epi-neocaesalpin L (8). Their planar structures and absolute configurations were fully determined by comprehensive spectroscopic methods, including 2D NMR and electronic circular dichroism spectra. Compounds 1-4 are tetracyclic cassane diterpenoids possessing a furan ring, and compounds 5-10 are tetracyclic cassane diterpenoids possessing a fused butenolide moiety. The anti-inflammatory and cytotoxic activities of the isolates were evaluated, while none of them showed obvious effects. The current study identified ten new cassane-type diterpenoids from the seeds of C. bonduc (L.) Roxb., which enriched the chemical diversity of the titled herbal medicine.

Pterolobirins A and B, Oxygen-Bridged Cassane Diterpenoid Dimers from the Fruits of Pterolobium macropterum

Two dimeric cassane diterpenoids with an unprecedented 6/6/6/6/6/5/6/6/6 nonacyclic framework, pterolobirins A and B (1 and 2), were isolated from the fruits of Pterolobium macropterum. Their structures were assigned by interpreting the spectroscopic data. The absolute configuration of 1 was unequivocally confirmed by single-crystal X-ray diffraction data. A putative biosynthetic pathway is proposed based on a regular intermolecular Diels-Alder reaction and an intramolecular nucleophilic addition.

Cassane Diterpenoids from the Aerial Parts of Caesalpinia pulcherrima and Their Antifeedant and Insecticidal Activities against Mythimna separate and Plutella xylostella

Ten new cassane diterpenoids, caesalpulcherrins A-J (1-10), together with 11 known analogues (11-21) were isolated from the aerial parts of Caesalpinia pulcherrima. Their structures and relative stereochemistry were elucidated by spectrometric and spectroscopic methods, including one-dimensional (1D) and two-dimensional (2D) NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and single-crystal X-ray diffraction analysis. Compounds 1-4 represent the first examples of 2,5-dimethoxyfuranocassane diterpenoids. Results of the antifeedant activity indicated that isovouacapenol C (12) and pulcherrin N (14) exhibited remarkable antifeedant activity against Mythimna separate with EC₅₀ values of 3.43 and 4.20 μg/cm², respectively. Meanwhile, pulcherrimin C (13) and 12-demethyl neocaesalpin F (18) exerted significant antifeedant activity against Plutella xylostella with an EC₅₀ data of 4.00 and 3.05 μg/cm², respectively. Some of the compounds showed obvious toxic activity against the plant-feeding generalist insect herbivores, M. separate and P. xylostella, at 0.8 mg/mL (800 ppm). Furthermore, the structure-activity relationships of antifeedant and insecticidal activities are also discussed in the article.

Caesalpanins A-C, Three Dimeric Cassane Diterpenoids from the Seeds of Caesalpinia sappan L

Three dimeric cassane diterpenoids, caesalpanins A-C, were isolated from the seeds of Caesalpinia sappan L., as well as three known compounds. Their structures were determined via analysis of 1D-, 2D-NMR, and HR-ESI-MS data. Caesalpanins A and B were the second and third compounds that presented a nitrogen-containing cassane diterpenoid dimer linked through one ether bond between C-19 and C-20'. Caesalpanin B exhibited moderate cytotoxic activity against MCF-7 cell lines with IC₅₀ value of 29.98 μm. Caesalpanins A and B had weak inhibitory effects against LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages at 50 μm with inhibitory rate of 36.01 % and 32.93 %, respectively.

Survey of natural products reported by Asian research groups in 2016

The new natural products reported in peer-reviewed articles in 2016 in journals with good reputations were reviewed and analyzed. The advances that Asian research groups made in the field of natural products chemistry in 2016 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on structural classification.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, abietanes, pimaranes, kauranes, cembranes and their cyclization products. The literature from January to December, 2016 is reviewed.

Diterpenoids of the Cassane Type from Caesalpinia decapetala

Eighteen compounds, including eight new cassane-type furanoditerpenoids, 3β-hydroxyphanginin H (1), 3β-acetoxyphanginin H (2), 7β-acetoxyphanginin H (3), 7β-hydroxyphanginin H (4), 4-epi-3β-hydroxycaesalpinilinn (5), 4-epi-3β-acetoxycaesalpinilinn (6), 20-acetoxytaepeenin D (7), and tomocin E (8), along with 10 known compounds (9-18) were isolated from the roots of Caesalpinia decapetala. Compounds 1-13 were isolated from C. decapetala for the first time. The new compounds with their absolute configurations were determined by extensive spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Compounds 1, 4, 5, 7, and 11 exhibited inhibitory activities against the SW1990 human pancreatic cancer cell line with IC₅₀ values ranging from 2.9 to 8.9 μM.