Baccaramiones A-D, Four Highly Oxygenated and Rearranged Trinorditerpenoids from Baccaurea ramiflora

Ramifloraolides A - D, four highly oxygenated picrotoxane-type sesquiterpenoids from the stems of Baccaurea ramiflora and their antithrombotic activity

A phytochemical investigation of the ethanol extract from air-dried stems of Baccaurea ramiflora led to the isolation of four highly oxygenated picrotoxane-type sesquiterpenoids, ramifloraolides A - D (1-4). Their structures were elucidated by comprehensive spectroscopic data (HRESIMS, IR, 1D, and 2D NMR), and their absolute configuration of them were unambiguously determined by single-crystal X-ray diffraction. Structurally, all compounds possess a unique [4.3.0] bicyclic core along with a characteristic γ-lactone. Notably, compound 1 is a picrotoxane sesquiterpenoid incorporating a rare oxygen bridge and a pentadecolactone. Compounds 2-4 possess a five-membered ether ring and the pentadecolactone, while ramifloraolides C (3) and D (4) were nor-picrotoxane. Then, the isolated phytochemicals were evaluated for antithrombotic activity in vivo. Interestingly, compounds 1 and 2 displayed potent antithrombotic activity at 30 μM in a zebrafish model. Additionally, 1 and 2 demonstrated certain antithrombotic effects in a mouse model of thrombosis. This marked the first report on the anti-thrombotic activity of picrotoxane-type sesquiterpenoids. Furthermore, network pharmacological and molecular docking analysis revealed potent target of those compounds associated with thrombotic disease. These finding initially demonstrate the potential of picrotoxanes as naturally derived antithrombotic lead compounds, and highlight the significant research values of sesquiterpenoids from the Baccaurea genus for comprehensive exploration of their application in antithrombotic therapy.

Highly oxygenated steroids with immunosuppressive activity from Solanum undatum

Solanum undatum is a medicinal plant used for the treatment of oedema, rheumatoid arthritis and toothache, from which seven highly oxygenated steroids (1-7), including three new ones (1-3), have been characterized. Compound 1 is a new steroidal carboxylic acid featuring a cyclohexa-2,5-dien-1-one moiety and compounds 2 and 3 are new withanolide analogs with a 1,6-dimethyl-3,7-dioxabicyclo[4.1.0]heptan-2-ol terminus. Their structures and absolute configurations were determined by a combination of spectroscopic data, quantum chemical calculations, single-crystal X-ray diffraction, and the NMR-based phenylglycine methyl ester (PGME) method. An immunosuppressive activity assay revealed that compounds 2-7 exhibited substantial activities against the proliferation of T and B lymphocytes in vitro, with IC50 values ranging from 1.60 to 7.89 μM and 0.90 to 6.90 μM, respectively. Notably, compound 6 showed selective inhibitory effect toward B cells with the highest selective index (SI = 40.5). Preliminary structure-activity relationships of compounds 1-7 suggest that the terminal 1,6-dimethyl-3,7-dioxabicyclo[4.1.0]heptan-2-ol or 5,5-spiroacetal moiety is critical for immunosuppressive activity. Our study indicated that they could be promising lead compounds for immunosuppressive agents.

Survey of natural products reported by Asian research groups in 2023

The new natural products reported in 2023 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2023 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Immunosuppressive Breviane Spiroditerpenoids from Penicillium bialowiezense Isolated from a Medicinal Plant

Breviane spiroditerpenoids are a small group of structurally interesting and complex meroterpenoids. This work focused on an endophytic fungus Penicillium bialowiezense ZBWPQ-27 that was isolated from a medicinal plant Euphorbia neriifolia, leading to the isolation of 15 breviane spiroditerpenoids with four types of polycyclic systems (1-6 and 9-17), and two new carotane sesquiterpenoids (7 and 8). The structures including absolute configurations of the new compounds 1-8 were elucidated by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. In addition, the misassigned NMR data of several resonances of the 5-methyl-TAL motif (E ring) in those of known brevianes (9-15) were corrected by spectroscopic data analysis. Biological tests revealed that brevianes with the type A ring system (6/6/6/5/6) showed moderate to significant immunosuppressive activities, and compound 11 displayed the most potent inhibitory activities against concanavalin A (ConA)-induced T cell proliferation (IC50 4.1 ± 0.2 μM) and lipopolysaccharide (LPS)-induced B cell proliferation (IC50 4.6 ± 0.2 μM), with good SI values of 28 ± 2 and 25 ± 4, respectively.

Stereochemical insights into enantioselective antiplasmodial lignanamides from the twigs and leaves of Solanum erianthum

Stereochemical investigations on the twigs and leaves of Solanum erianthum afforded five pairs of lignanamide enantiomers and a previously undescribed phenolic amide (3). Particularly, two pairs of previously undescribed lignanamide racemates (1a/1b-2a/2b) represent the first case of natural products that feature an unreported 5/5-fused N/O-biheterocyclic core. Their structures, including the absolute configurations, were determined unambiguously by using spectroscopic analyses and electronic circular dichroism calculations. A speculative biogenetic pathway for 1-3 was proposed. Interestingly, these lignanamides exhibited enantioselective antiplasmodial activities against drug-sensitive Plasmodium falciparum 3D7 strain and chloroquine-resistant Plasmodium falciparum Dd2 strain, pointing out that chirality plays an important role in drug development.

Highly modified cephalotane-type diterpenoids from Cephalotaxus fortunei var. alpina and C. sinensis

Cephalotanes are a rare class of diterpenoids occurring exclusively in Cephalotaxus plants. The intriguing structures and promising biological activities for this unique compound class prompt us to investigate C. fortunei var. alpina and C. sinensis, leading to the isolation of six undescribed cephalotane-type diterpenoids and/or norditerpenoids, ceforloids A-F (1-6). Their structures were elucidated by comprehensive analysis of spectroscopic data, including ECD and single-crystal X-ray diffraction studies, as well as quantum chemical calculations. Compound 1 possesses an unprecedented norditerpenoid skeleton featuring an unusual acetophenone moiety, and originated putatively from a disparate biogenetic pathway. Compounds 4 and 5 incorporate a unique 12,13-p-hydroxybenzylidene acetal motif. Compound 6 is a rare cephalotane-type diterpenoid glycoside. Immunosuppressive assays showed that compounds 2 and 6 exhibited mild suppressive activity against the activated T and B lymphocytes proliferation. These findings not only expanded the structural diversity of this small group of diterpenoids, but also explored their potential as novel structures for the development of immunosuppressive agents.

Sesquiterpenoids and Cytochalasins with Immunosuppressive Activity from Sonchus wightianus

The plant species, Sonchus wightianus DC., was historically used in China for both medicinal and dietary uses. In present study, seven new guaiane sesquiterpenoids (1-7) and one cytochalasin (8), along with five known guaianes (9-13) and two known cytochalasins (14 and 15), were isolated from the whole plants of S. wightianus. These guaianes showed structural variations in the substituents at C-8 and/or C-15, and compounds 6 and 7 are two sesquiterpenoid glycoside derivatives. Their structures were determined by extensive analysis of spectroscopic, electronic circular dichroism, and X-ray diffraction data, and chemical method. Biological tests revealed that compounds 5 and 8 are potent and selective immunosuppressive reagents.

A Comprehensive Review of the Classification, Sources, Phytochemistry, and Pharmacology of Norditerpenes

Norditerpenes are considered to be a common and widely studied class of bioactive compounds in plants, exhibiting a wide array of complex and diverse structural types and originating from various sources. Based on the number of carbons, norditerpenes can be categorized into C19, C18, C17, and C16 compounds. Up to now, 557 norditerpenes and their derivatives have been found in studies published between 2010 and 2023, distributed in 51 families and 132 species, with the largest number in Lamiaceae, Euphorbiaceae, and Cephalotaxaceae. These norditerpenes display versatile biological activities, including anti-tumor, anti-inflammatory, antimicrobial, and antioxidant properties, as well as inhibitory effects against HIV and α-glucosidase, and can be considered as an important source of treatment for a variety of diseases that had a high commercial value. This review provides a comprehensive summary of the plant sources, chemical structures, and biological activities of norditerpenes derived from natural sources, serving as a valuable reference for further research development and application in this field.

Diterpenoids from Euphorbia lactea and their anti-HIV-1 activity

Nine undescribed diterpenoids, euphlactenoids A-I (1-9), including four ingol-type diterpenoids (1-4) with a 5/3/11/3-tetracyclic framework and five ent-pimarane-type diterpenoids (5-9), together with thirteen known diterpenoids (10-22), were identified from the leaves and stems of Euphorbia lactea Haw. The structures and absolute configurations of compounds 1-9 were unequivocally elucidated on the basis of spectroscopic analysis, ECD calculations and single crystal X-ray diffraction. Compounds 3 and 16 showed anti-HIV-1 effects with IC₅₀ values of 1.17 μM (SI = 16.54) and 13.10 μM (SI = 1.93), respectively.

Strophiofimbrins A and B: Two Rearranged Norditerpenoids with Novel Tricyclic Carbon Skeletons from Strophioblachia fimbricalyx

Two rearranged norditerpenoids with novel tricyclic carbon skeletons, strophiofimbrin A (1) and strophiofimbrin B (2), were isolated from Strophioblachia fimbricalyx. Their structures were established by 1D/2D NMR spectroscopy, HRESIMS, quantum chemistry calculations, and X-ray diffraction analyses. 1 and 2 represented the first examples of diterpenoids with unprecedented 5/6/7-fused ring systems. In the proposed biosynthetic pathway, they were suspected to derive from cleistanthane norditerpenoids via ring opening, expansion, cyclization, and rearrangement based on the existence of phenanthrenone and cleistanthane diterpenoids from Strophioblachia and Trigonostemon, two closely related genera of the Euphorbiaceae family. Furthermore, compounds 1 and 2 exhibited significant proliferation inhibition and obvious neuroprotective effects.