Structure-activity relationships of natural and synthetic lathyrane-based diterpenoids for suppression of NLRP3-driven inflammation and gouty arthritis.

Lathyrane-based diterpenoid is one of the critical bioactive elements of Euphorbia lathyris L., a widely used traditional Chinese medicine for the treatment of inflammation and infection. In this study, we introduced and evaluated seven synthetic or natural lathyrane-based diterpenoids with the same core structure but notable structural variations at specific positions, for their anti-inflammatory and gout-alleviating properties. There was no significant cytotoxicity below 10 µM among the initial test of the cell counting kit 8 of the seven candidate derivatives (compounds 13 to 19) in this work. Furthermore, maintaining the acyloxy group at 15-C position and the strongly hydrophobic aryl structure at 3-C and 5-C positions, compounds 15 (Euphorbia factor L3, EFL3) and 17 strikingly inhibited the production of IL-1ß related to the actuation of the inflammasome in our study. The ELISA assay indicated that the anti-inflammatory effects of EFL3 were better associated with MSU stimulation than other second-line pathways triggered by inflammasome. Further examinations on the acute paw gout model in C57BL/6 mice showed that EFL3 had a significantly inflammatory retarding effect by intraperitoneal injection. It decreased swelling volume as well as the cleavage and activation of local IL-1ß and casepas-1 in the paw. To conclude, our findings reveal several potential key structure-activity relationships that govern the anti-inflammatory effects of lathyrane-type diterpenoids, the dispensable acyl group at the 15-C position, the importance of maintaining the spatial structure of the B-ring, and the potential importance of hydrophobic substituents at the 3-C position. These insights may provide guidance for the structural design of lathyrane-type agents in the future; furthermore, we found that the lathyrane-based diterpenoid EFL3 is a potential agent for gout that is expected to provide a novel therapeutic strategy for inflammation intervention.

Synthesis, antiproliferative and anti-MDR activities of lathyrane diterpene derivatives based on configuration inversion strategy.

A series of lathyrane-type Euphorbia diterpene derivatives featured 3R configuration (H-3ß) were synthesized from natural rich Euphorbia factor L3via modified Mitsunobu reaction based on configuration inversion strategy. The antiproliferation activity and MDR reversal ability of the lathyrane derivatives were evaluated, and the most synthesized compounds showed moderate or strong potencies. Among them, diterpenes 21 (IC50 values of 2.6, 5.2 and 13.1 µM, respectively) and 25 (IC50 values of 5.5, 8.6 and 1.3 µM, respectively) presented the strong cytotoxicity against MCF-7, 4 T1 and HepG2 cells. Meanwhile, derivative 25 exhibited excellent MDR reversal ability with the reversal fold of 16.1 higher than that of verapamil. The cellular thermal shift assay and molecular docking proved direct engagement of diterpene 25 to ABCB1, suggesting 25 could be a promising MDR modulator. Furthermore, the preliminary SARs of these diterpenes were also discussed.

Lathyrane-Type Diterpenoids from the Seeds of Euphorbia lathyris L. with Inhibitory Effects on NO Production in RAW 264.7 Cells.

Bioactivity-guided fractionation of the methanolic extract from the seeds of Euphorbia lathyris led to the isolation of 18 lathyrane-type diterpenoids including a new one, Euphorbia factor L29 (1). Their chemical structures were elucidated by extensive NMR spectroscopic data including 2D-NMR and HR-ESI-MS as well as CD data. All isolates (1 - 18) were found to inhibit the nitric oxide production in LPS-induced RAW 264.7 macrophages, with their IC50 values in the range of 11.2 - 52.2 µm.

Genkwalathins A and B, new lathyrane-type diterpenes from Daphne genkwa.

Screening for new natural anti-neuroinflammatory compounds was performed with the traditional folk medicine Genkwa Flos, which potently inhibited nitric oxide (NO) production by LPS-activated microglial BV-2 cells. Two new lathyrane-type diterpenes, genkwalathins A (1) and B (2), and 14 known daphnane-type diterpenes (3-16) were isolated. The lathyrane-type diterpenes were isolated for the first time from the Thymelaeaceae family in this study. Compounds 1 and 2 moderately inhibited LPS-induced NO production in BV-2 cells without affecting cell viability, while six daphnane-type diterpenes (3, 4, 6, 7, 9 and 10) potently reduced NO production with IC50 values less than 1 µM, although they did display weak cytotoxicity. A structure-activity relationship study on the daphnane-type diterpenes indicated that the stereochemistry at C-19, the benzoate group at C-20, and the epoxide moiety could be important for their anti-neuroinflammatory effects.

Lathyrane-type diterpenoids from the seeds of Euphorbia lathyris.

Ten lathyrane-type diterpenoids named Euphorbia Factor L12-L21 (1-10) and twelve known diterpenoids (11-22) were isolated from seeds of Euphorbia lathyris. The structures of these compounds were determined by extensive spectroscopic (UV, IR, HRESIMS, 1D and 2D NMR) analyses. In addition, the configuration of Euphorbia Factor L12 (1) was further confirmed by X-ray crystallographic and circular dichroism (CD) analyses. A putative biogenetic relationship to these compounds was proposed. Cytotoxicity of the isolated compounds against C6 and MCF-7 cell lines were evaluated. Compounds 1, 5, 7, 12 and 17 exhibited considerable cytotoxic activities (IC50 12.4-36.2 µM).