Biscroyunoid A, an Anti-Hepatic Fibrotic 19-nor-Clerodane Diterpenoid Dimer with a C-16-C-12' Linkage from Croton yunnanensis.

Biscroyunoid A (1), a 19-nor-clerodane diterpenoid dimer featuring a unique C-16-C-12' linkage and containing an unusual 4,7-dihydro-5H-spiro[benzofuran-6,1'-cyclohexane] motif, together with its biosynthetic precursor, croyunoid A (2), were isolated from Croton yunnanensis. Their structures were determined by spectroscopic, computational, and single-crystal X-ray diffraction methods. Compound 1 exerted an antihepatic fibrosis effect in LX-2 cells via inhibition of TGFß-Smad2/3 signaling.

Discovery of Ingenane Diterpenoids from Euphorbia hylonoma as Antiadipogenic Agents.

Thirteen new Euphorbia diterpenoids, euphylonanes A-M (1-13), and eight known ones were isolated from the whole plants of Euphorbia hylonoma. Compounds 1 and 2 are two rearranged ingenanes bearing a rare 6/6/7/3-fused ring system. Compound 3 represents the first example of a 9,10-epoxy tigliane, while 4-21 are typical ingenanes varying with substituents. Structures were elucidated using a combination of spectroscopic, computational, and chemical methods. Most ingenanes exerted a significant antiadipogenic effect in 3T3-L1 adipocytes, among which 4 was the most active with an EC50 value of 0.60 ± 0.27 µM. Mechanistic study revealed that 4 inhibited the adipogenesis and lipogenesis in adipocytes via activation of the AMPK signaling pathway.

Discovering a New Okadaic Acid Derivative, a Potent HIV Latency Reversing Agent from Prorocentrum lima PL11: Isolation, Structural Modification, and Mechanistic Study.

Marine toxins (MTs) are a group of structurally complex natural products with unique toxicological and pharmacological activities. In the present study, two common shellfish toxins, okadaic acid (OA) (1) and OA methyl ester (2), were isolated from the cultured microalgae strain Prorocentrum lima PL11. OA can significantly activate the latent HIV but has severe toxicity. To obtain more tolerable and potent latency reversing agents (LRAs), we conducted the structural modification of OA by esterification, yielding one known compound (3) and four new derivatives (4-7). Flow cytometry-based HIV latency reversal activity screening showed that compound 7 possessed a stronger activity (EC50 = 46 ± 13.5 nM) but was less cytotoxic than OA. The preliminary structure-activity relationships (SARs) indicated that the carboxyl group in OA was essential for activity, while the esterification of carboxyl or free hydroxyls were beneficial for reducing cytotoxicity. A mechanistic study revealed that compound 7 promotes the dissociation of P-TEFb from the 7SK snRNP complex to reactivate latent HIV-1. Our study provides significant clues for OA-based HIV LRA discovery.

Discovery of Highly Potent Daphnane Diterpenoids Uncovers Importin-ß1 as a Druggable Vulnerability in Castration-Resistant Prostate Cancer.

Importins are overexpressed in many cancers and mediate the abnormal nuclear transport of oncogenic factors. The druggable potential of importins still remains unclear, largely because of the lack of potent inhibitors. Herein, the anti-castration-resistant prostate cancer (CRPC) screening of a Euphorbiaceae diterpenoid library followed by target fishing led to the identification of a highly potent importin-ß1 inhibitor, daphnane diterpenoid DD1. DD1 selectively inhibited the growth and survival of CRPC cells at subnanomolar concentrations and completely blocked tumor growth in preclinical models at an extremely low dosage. Mechanistic studies revealed that targeting of importin-ß1 by DD1 significantly reduced the nuclear accumulation of key CRPC drivers, shutting down their downstream oncogenic signaling. Disruption of the predicted binding sites of DD1 on importin-ß1 abolished this anti-CRPC effect. These findings suggest that importin-ß1 is an effective therapeutic target in CRPC and that DD1 as the most potent importin-ß1 inhibitor to date can be developed as therapeutics for treatment of this disease.

Crotonianoids A-C, Three Unusual Tigliane Diterpenoids from the Seeds of Croton tiglium and Their Anti-Prostate Cancer Activity.

Crotonianoids A-C (1-3), three unusual tigliane diterpenoids, were isolated from the seeds of Croton tiglium. Compound 1 is a 13,14:13,15-diseco-tigliane featuring a unique spiro[bicyclo[5.3.0]decane-2,5'-2'(3'H,4'H)-furanone] core; 2 is a 13,15-seco-tigliane incorporating a rare peroxide bridge between C-13 and C-15; and 3 is the first example of a phorbol ester with a 10R-configuration. Their structures were determined by spectroscopic, computational, and X-ray diffraction methods. Compounds 1 and 2 markedly inhibited the growth and survival of prostate cancer cell C4-2B at micromolar concentrations and induced cell apoptosis. Mechanistic study revealed that 1 and 2 could suppress androgen receptor (AR) signaling pathway by promoting the degradation of AR protein.

Tigliane and rhamnofolane glycosides from Euphorbia wallichii prevent oxidative stress-induced neuronal death in PC-12 cells.

Tigliane and rhamnofolane diterpenoids bearing glycosyl substituents are rarely found in nature. In the current study, seven new tigliane glycosides, euphorwallsides A - G (1-7), and five new rhamnofolane glycosides, euphorwallsides H - L (8-12), were isolated from the whole plants of Euphorbia wallichii. Their structures were elucidated by a combination of spectroscopic, computational, and chemical means. The aglycones of 1-5 represent a rare class of 13-deoxygenated tiglianes, while those of 8-12 represent the first examples of 4-deoxygenated rhamnofolanes. 2, 3, 5, 7, 8, and 12 showed significant neuroprotective effects on sodium nitroprusside (SNP)-induced neuronal death in pheochromocytoma cell line PC-12 at 10 µM, being more active than the clinical drug, edaravone. Mechanistic study revealed that the most active compound, 3, could inhibit reactive oxygen species (ROS) accumulation and restore the mitochondrial membrane potential via modulating the Nrf2 signaling pathway in PC-12 cells.

Natural product-based screening led to the discovery of a novel PXR agonist with anti-cholestasis activity.

Cholestasis is a major cause of a series of bile flow malfunction-related liver diseases. Pregnane X receptor (PXR) is a key regulator in endo- and xeno-biotics metabolism, which has been considered as a promising therapeutic target for cholestasis. In this study we conducted human PXR (hPXR) agonistic screening using dual-luciferase reporter gene assays, which led to discovering a series of potent hPXR agonists from a small Euphorbiaceae diterpenoid library, containing 35 structurally diverse diterpenoids with eight different skeleton types. The most active compound 6, a lathyrane diterpenoid (5/11/3 ring system), dose-dependently activated hPXR with a high selectivity, and significantly upregulated the expression of hPXR downstream genes CYP3A4 and UGT1A1. In LCA-induced cholestasis mouse model, administration of compound 6 (50 mg· kg-1. d-1, ip) for 7 days significantly suppressed liver necrosis and decreased serum levels of AST, ALT, Tbili, ALP, and TBA, ameliorating LCA-induced cholestatic liver injury. We further revealed that compound 6 exerted its anti-cholestatic efficacy via activation of PXR pathway, accelerating the detoxification of toxic BAs and promoting liver regeneration. These results suggest that lathyrane diterpenoids may serve as a promising scaffold for future development of anti-cholestasis drugs.

Homo/Hetero-Dimers of Aromatic Bisabolane Sesquiterpenoids with Neuroprotective Activity from the Fungus Aspergillus versicolor A18 from South China Sea

Chromatographic fractionation of the EtOH extracts of the marine-derived fungus Aspergillus versicolor A18 has led to the isolation of 11 homo/hetero-dimers of aromatic bisabolane sesquiterpenoids including eight diphenyl ether-coupled aromatic bisabolanes (1a/1b and 5−10) and three homodimers (2−4), together with their monomers including three aromatic bisabolanes (11−13) and two diphenyl ethers (14 and 15). Their structures and absolute configurations were elucidated by extensive spectroscopic analysis including HRESIMS, 1D/2D NMR, calculated ECD, and the optical rotatory data. Among the four new compounds, (+/−)-asperbisabol A (1a/1b), asperbisabol B (2), and asperbisabol C (3), the enantiomers 1a and 1b represent an unprecedented skeleton of diphenyl ether-coupled aromatic bisabolane sesquiterpenoids with a spiroketal core moiety. The neuroprotective effects of selected compounds against sodium nitroprusside (SNP)-induced injury were evaluated in PC12 cells by the MTT assay. Five compounds (1a, 6, and 8−10) showed remarkable neuroprotective activities at 10 µM, being more active than the positive control edaravone.

Selaginellins from the genus Selaginella: isolation, structure, biological activity, and synthesis.

Covering: 2007 to 2020 Selaginellins are a small group of pigments exclusively found in the ancient genus Selaginella. Since the first report of selaginellin from S. sinensis in 2007, more than 110 selaginellins with diverse polyphenolic skeletons have been reported. This review provides extensive coverage of the selaginellins discovered from 2007 to 2020, including 61 natural ones and 52 synthetic analogues. The isolation, chemical structures, plausible biosynthetic pathways, bioactivity, and total synthesis of these selaginellins have been summarized for the first time, and this highlights the fact that the vast uninvestigated Selaginella species may serve as a potential treasure trove of chemically diverse selaginellins waiting to be discovered.

Total Synthesis of Mulberry Diels-Alder-Type Adducts Kuwanons G and H.

Mulberry Diels-Alder-type adducts (MDAAs) are a group of rare natural polyphenols biosynthetically derived from [4 + 2]-cycloaddition of chalcones and dehydroprenylphenols. In this study, kuwanons G (1) and H (2), two bioactive MDAAs with unique dehydroprenylflavonoid dienes, were totally synthesized for the first time in a biomimetic manner. The key features of the convergent route include the use of the Baker-Venkataraman rearrangement, alkylation of ß-diketone, intramolecular cyclization, and Suzuki-Miyaura coupling to achieve the subunit diene.

Structural Elucidation of Three 9,11-Seco Tetracyclic Triterpenoids Enables the Structural Revision of Euphorol J.

Compounds 1-3, the rare examples of 9,11-seco euphane or lanostane triterpenoids featuring an enol-hemiacetal functionality, were isolated from Euphorbia stracheyi. Their structures were elucidated by a combination of spectroscopic, computational, chemical, and single-crystal X-ray diffraction means, which enables the structure of previously published euphorol J to be revised as 1. 1-3 showed significant cytotoxicities on the breast cancer cell line MDA-MB-468 with IC50 values in the range of 2.9-3.9 µM.

Presegetane diterpenoids from Euphorbia sieboldiana as a new type of anti-liver fibrosis agents that inhibit TGF-ß/Smad signaling pathway.

Seven new diterpenoids, eupholenes A-G (1-7), including two presegetanes (1 and 2), four jatrophanes (3-6), and one paraliane (7), along with 19 known analogues (8-26) were obtained by anti-liver fibrosis bioassay-guided isolation of Euphorbia sieboldiana. Their structures were elucidated by extensive spectroscopic data analyses, chemical methods, ECD calculations, and single-crystal X-ray diffractions. Euphorbesulin A (10), a presegetane diterpenoid (5/9/5 ring system), was identified as a promising anti-liver fibrosis agent that could inhibit the expressions of fibronectin (FN), α-smooth muscle actin (α-SMA), and collagen I in TGF-ß1-stimulated LX-2 cells at a micromolar level. Mechanistic study revealed that 10 suppressed liver fibrosis via inhibition of TGF-ß/Smad signaling pathway, and its potential target was TGF-ß type I receptor. These findings suggested that presegetane diterpenoid could serve as a new type of structural motif in future anti-liver fibrosis drug development.

Salviplenoid A from Salvia plebeia attenuates acute lung inflammation via modulating NF-κB and Nrf2 signaling pathways.

Acute lung injury (ALI) involves series of inflammatory pathologies and cause high morbidity. Salviplenoid A (SA) was a new sesquiterpenoid from the traditional inflammatory herb Salvia plebeia. In our previous study, SA exhibited antiinflammatory activity in RAW264.7 cells. However, the extensive effects of SA in human cells and in vivo and the active mechanisms are unclear. Thus, in this study, we sought to access its effects in vitro and in vivo and to investigate its mechanisms. SA was proved to inhibit the induction of proinflammatory cytokines in human cell types, including pulmonary epithelial cells and endothetial cells. It also depressed monocyte adhesion. Moreover, SA potently attenuated the acute lung inflammation in the LPS-induced mouse model shown by down-regulation of proinflammatory mediators, inhibition of polymorphonuclear neutrophil infiltration, and alleviation of related symptoms like alveolar congestion and mucus secretion. Further evaluation confirmed that SA regulated NF-κB pathway by inhibiting the IκB-α phosphorylation. And it markedly mediated Nrf2/HO-1 pathway by activating the Nrf2/HO-1 expression and promoting Nrf2 nuclear translocation. Therefore, SA could attenuate acute lung inflammation via suppressing NF-κB and activating Nrf2, which provide a theoretical basis for the potential application of SA in clinic.

Spiroconyone A, a new phytosterol with a spiro [5,6] ring system from Conyza japonica.

Spiroconyone A (1), the first rearranged phytosterol featuring an unusual spiro [5,6] ring system, and nine known compounds (2-10) were isolated from the aerial parts of Conyza japonica. The structure of 1 was elucidated through spectroscopic methods, and its absolute configuration was determined by single-crystal X-ray diffraction analysis. Enzyme-based assay revealed that spiroconyone A showed weak TDP1 inhibition and compounds 7 and 10 showed TDP1 inhibition with IC50 values of 36 µM and 16 µM, respectively. MTT assay indicated that 7 and 10 showed a strong synergistic effect with the clinical TOP1 inhibitor topotecan in MCF-7 cells. Compound 5 displayed the most potent cytotoxicity against MCF-7 cells with a GI50 value of 3.3 µM. Furthermore, a hypothetical biosynthetic pathway for 1 was proposed. This work provides valuable information that the secondary metabolites from Conyza japonica could be developed as anticancer agents.

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.

Ingol diterpenoids as P-glycoprotein-dependent multidrug resistance (MDR) reversal agents from Euphorbia marginata.

Twenty new ingol diterpenoids, euphornans A-T (1-20), representing a rare class of C-19-oxidated and H-2, H-3 ß-oriented ingols, were isolated from the seeds of Euphorbia marginata. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis, ECD analysis, and single crystal X-ray diffraction. Compounds 1-20 were screened for the multidrug resistance (MDR) reversal activity on P-glycoprotein (Pgp)-dependent MDR cancer cell line HepG2/ADR, and 11, 14, and 18 were identified as potent MDR modulators that could enhance the efficacy of anticancer drug adriamycin to ca. 20 folds at 5 µM. The Pgp inhibition mechanism and brief structure-activity relationships (SARs) of these compounds were also discussed.

Mannosylxylarinolide, a new 3,4-seco-ergostane-type steroidal saponin featuring a ß-d-mannose from the endophytic fungus Xylaria sp.

Mannosylxylarinolide (1), a new 3,4-seco-ergostane-type steroidal saponin featuring a ß-d-mannose moiety, was isolated from the culture of the endophytic fungus Xylaria sp. that had been isolated from an ornamental plant of Hoya sp. The gross structure was determined by spectroscopic data, and the absolute configuration of the new 3,4-seco-ergostane-type steroidal saponin (1) was determined by X-ray diffraction analysis.

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.

Euphorhelipanes A and B, Triglyceride-Lowering Euphorbia Diterpenoids with a Bicyclo[4.3.0]nonane Core from Euphorbia helioscopia.

Euphorhelipanes A (1) and B (2), two Euphorbia diterpenoids with a new 4-(5,5-dimethylheptan-2-yl)-2,7-dimethylbicyclo[4.3.0]nonane skeleton, were isolated from a 95% ethanol extract of the whole plants of Euphorbia helioscopia. Their structures were elucidated by spectroscopic data analysis, quantum chemical calculations, and single-crystal X-ray diffraction data. Compounds 1 and 2 represent the first examples of Euphorbia diterpenoids with a 5/6 fused carbon ring system, and their plausible biosynthetic pathways originating from jatrophanes are proposed. Compounds 1 and 2 showed a triglyceride-lowering effect in oleic-acid-stimulated HuH7 cells at concentrations of 1-50 µM.