19-nor-, 20-nor-, and tetranor-Halimane-Type Furanoditerpenoids from Croton crassifolius.

The phytochemical investigation of the roots of Croton crassifolius led to the isolation of 16 new halimane furanoditerpenoids, crohalifuranes A-P (1-16), along with 15 known analogues, 17-31. The new structures including their absolute configurations were elucidated by NMR and MS data analysis, comparison of experimental and calculated electronic circular dichroism data, single-crystal X-ray diffraction data, and chemical methods. Crohalifuranes A (1) and B (2) are tetranor- and 19-nor-halimane diterpenoids featuring a rare decahydroacenaphthene core, respectively, which might be derived from the accompanying crassifoliusin A by loss of the furan ring or the C-19 substituent. Crohalifurane C (3) represents the first example of a 20-nor-halimane diterpenoid, and crohalifurane D (4) is characterized by an unusual 6,20-δ-lactone moiety. All compounds were examined for their inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide in RAW264.7 cells, and 2 and 23 exhibited moderate inhibition on NO production with IC50 values of 17.2 ± 1.3 and 23.7 ± 1.4 µM, respectively.

Euphoresulanes A-M, structurally diverse jatrophane diterpenoids from Euphorbia esula.

Thirteen new jatrophane diterpenoids, euphoresulanes A-M (1-13), and seven known analogues (14-20) were isolated from the whole plants of Euphorbia esula. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configurations of 1, 6, and 10 were confirmed by single crystal X-ray diffraction. Compounds 1-20 were screened for the multidrug resistance (MDR) reversal activity on P-glycoprotein (Pgp)-dependent cancer cell line HepG2/ADR, and 1, 2, 4, 6, and 8 exhibited comparable activity to the positive drugs. Euphoresulane H (8), the most active MDR modulator, could enhance the efficacy of anticancer drug adriamycin to ca. 33 folds at 5 µM. The structure-activity relationship (SAR) study revealed that the acyloxy substitution at C-9 is essential to the activity and presence of H-2 was favorable.

Two new ent-abietane diterpenoids from Euphorbia helioscopia.

Two new ent-abietane diterpenoids, euphcopenoids A (1) and B (2), along with six known analogues (3 - 8), were isolated from the whole plants of Euphorbia helioscopia. Their structures were determined by various spectroscopic methods (MS, UV, IR, and NMR), and the absolute configurations of compounds 1 and 2 were determined by quantum chemical ECD calculations. All compounds were screened for the cytotoxicity against A549 and HEPG2 cancer cell lines, but were inactive.[Formula: see text].

Two highly oxygenated nor-clerodane diterpenoids from Croton caudatus.

Two highly oxygenated nor-clerodane diterpenoids, crocleropenes A and B (1 and 2), together with four known compounds (3-6) were isolated from the leaves and twigs of Croton caudatus. Their structures were elucidated by combination of extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. 1 and 2 represent the first examples of nor-clerodane-3,5(10)-diene diterpenoids. Compounds 1 and 2 exhibited weak cytotoxicity in vitro against MCF-7 cancer cells with IC50 values of 35.8 and 40.2 µM, respectively. [Formula: see text].

A new prenylated coumarin and a new anthranilamide derivative from Evodia lepta.

A new prenylated coumarin (1) and a new anthranilamide derivative (2) were isolated from the aerial parts of Evodia lepta. Compound 2 represents the first anthranilamide derivative from the Evodia genus. Their structures were elucidated by spectroscopic data analysis (MS, UV, IR, and NMR). Compound 1 exhibited certain inhibition on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 macrophages with an IC50 value of 37.96 ± 1.7 µM.

Euphanoids A and B, two new lathyrane diterpenoids with nitric oxide (NO) inhibitory activity from Euphorbia kansuensis.

Two new lathyrane diterpenoids, euphanoids A and B (1 and 2), along with five known compounds (3-7) were isolated from the roots of Euphorbia kansuensis. Their structures were elucidated by spectroscopic analysis, and the absolute configuration of 1 was determined by single crystal X-ray diffraction. All of the isolates were screened for the inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 cells, and compounds 1 and 2 showed pronounced inhibition on NO production with IC50 values of 4.7 and 9.5 µM, respectively, being more active than the positive control, quercetin (IC50 = 10.8 µM).