Clerodane Diterpenoids Research Articles

Efficient production of clerodane and ent-kaurane diterpenes through truncated artificial pathways in Escherichia coli.

The clerodane and ent-kaurane diterpenoids are two typical categories of diterpenoid natural products with complicated polycyclic carbon skeletons and significant pharmacological activities. Despite exciting advances in organic chemistry, access to these skeletons is still highly challenging. Using synthetic biology to engineer microbes provides an innovative alternative to bypass synthetic challenges. In this study, we constructed two truncated artificial pathways to efficiently produce terpentetriene and ent-kaurene, two representative clerodane and ent-kaurane diterpenes, in Escherichia coli. Both pathways depend on the exogenous addition of isoprenoid alcohol to reinforce the supply of IPP and DMAPP via two sequential phosphorylation reactions. Optimization of these constructs provided terpentetriene and ent-kaurene titers of 66 ± 4 mg/L and 113 ± 7 mg/L, respectively, in shake-flask fermentation. The truncated pathways to overproduce clerodane and ent-kaurane skeletons outlined here may provide an attractive route to prepare other privileged diterpene scaffolds.

Two new clerodane diterpenoids and a new pyran-2-one derivative with anti-neuroinflammatory activities from Croton crassifolius.

Two new clerodane diterpenoids (1 and2), a new pyran-2-one derivative (3), along with five known compounds (4‒8), were isolated from Croton crassifolius. Notably, crassifolin X (1) is a novel clerodane diterpenoid, characterized with a peculiar δ-lactone core being formed between C-1 and C-4. Their structures, including absolute configurations, were established on the basis of spectroscopic methods (UV, IR, HRESIMS and NMR), and circular dichroism experiments. In addition, all compounds were evaluated for their anti-neuroinflammatory activities based on the expression of TNF-α and IL-6 levels on LPS-induced BV2 cells, and compounds 1‒3 and 5 showed potential anti-neuroinflammatory activity.

Clerodane furanoditerpenoids from the stems of Tinospora sinensis.

One new clerodane-type furanoditerpenoid tinosinoid A (1) and nine new nor-clerodane analogs tinosinoids B-J (2-10) have been isolated from the stems of Tinospora sinensis. The structures of the new compounds with absolute configurations have been elucidated by spectroscopic means, including MS, NMR and ECD techniques, as well as chemical correlation. Compound 1 is a rare sulfur-containing clerodane diterpenoid incorporating a 2-mercaptoethanol unit via a thioether bond, while compounds 4/5 and 9 represent two pairs of unusual equilibrium regioisomers through an interesting intramolecular transesterification. Our bioassays established that 1 and 8 displayed moderate antiproliferative effects against two human tumor cell lines, and 9 and 10 showed significant α-glucosidase inhibitory activities. A kinetics study revealed that compound 10 was a noncompetitive α-glucosidase inhibitor, and its possible binding mode to the enzyme was further probed by molecular docking experiments.

New clerodane diterpenoids from Solidago altissima and stereochemical elucidation via 13C NMR chemical shift analysis

Five new clerodane diterpenoids along with ten known compounds were isolated from the underground parts of Solidago altissima L. Compounds 1–4 were rare ent-neo-clerodanes with the cis A/B ring and a trans-configuration between the methyl groups at C-8 and C-9. Compound 5 was identified as trans-neo-clerodane. Revised stereochemical configurations for two known compounds were proposed. Additionally, the stereochemical configurations of the four stereogenic carbons in the 6/6 fused A/B rings of the clerodane diterpenoids were elucidated via 13C NMR spectral analysis. This analysis validated the proposed structural revisions and suggested the reassignments of other clerodane diterpenoids.

Clerodane diterpenoids with anti-inflammatory and synergistic antibacterial activities from Tinospora crispa

Compounds 5 and 7 exhibited nitric oxide release inhibitory activities with IC50 values of 7.5 and 10.6 μM, respectively, and compounds 9 and 14 at the sub-MIC level significantly decreased the MIC of oxacillin against MRSA from 32.0 to 1.0 and 0.5 μg mL−1, respectively.

Clerodane Diterpenoids from an Edible Plant Justicia insularis: Discovery, Cytotoxicity, and Apoptosis Induction in Human Ovarian Cancer Cells

Objectives: The toxicity of chemotherapeutic anticancer drugs is a serious issue in clinics. Drug discovery from edible and medicinal plants represents a promising approach towards finding safer anticancer therapeutics. Justicia insularis T. Anderson (Acanthaceae) is an edible and medicinal plant in Nigeria. This study aims to discover cytotoxic compounds from this rarely explored J. insularis and investigate their underlying mechanism of action. Methods: The cytotoxicity of the plant extract was evaluated in human ovarian cancer cell lines and normal human ovarian surface epithelia (HOE) cells using a sulforhodamine B assay. Bioassay-guided isolation was carried out using column chromatography including HPLC, and the isolated natural products were characterized using GC-MS, LC-HRMS, and 1D/2D NMR techniques. Induction of apoptosis was evaluated using Caspase 3/7, 8, and 9, and Annexin V and PI based flow cytometry assays. SwissADME and SwissTargetPrediction web tools were used to predict the molecular properties and possible protein targets of identified active compounds. Key finding: The two cytotoxic compounds were identified as clerodane diterpenoids: 16(α/β)-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide (1) and 16-oxo-cleroda-3,13(14)E-dien-15-oic acid (2) from the Acanthaceous plant for the first time. Compound 1 was a very abundant compound (0.7% per dry weight of plant material) and was shown to be more potent than compound 2 with IC50 values in the micromolar range against OVCAR-4 and OVCAR-8 cancer cells. Compounds 1 and 2 were less cytotoxic to HOE cell line. Both compounds induced apoptosis by increasing caspase 3/7 activities in a concentration dependent manner. Compound 1 further increased caspase 8 and 9 activities and apoptosis cell populations. Compounds 1 and 2 are both drug like, and compound 1 may target various proteins including a kinase. Conclusions: Clerodane diterpenoids (1 and 2) in J. insularis were identified as cytotoxic to ovarian cancer cells via the induction of apoptosis, providing an abundant and valuable source of hit compounds for the treatment of ovarian cancer.

Two pairs of epimers and three undescribed diterpenoids from Pseudocaryopteris paniculata

A phytochemical investigation on the petroleum ether partition of the whole plant of Pseudocaryopteris paniculata, yield seven new compounds: one phytanes diterpenoid (2Z,6E,10E) 14-keto-2,6,10-trimethyl pentadeca-2,6,10-trien-1-carboxylic acid (1), five clerodane diterpenoids: paniculatins A-E (2, 3a/3b, 4a/4b), one abietane diterpenoid: ent-uncinatone (5), together with 12 known compounds. Their structures were elucidated on the basis of 1D and 2D Nuclear Magnetic Resonance （NMR_, Infrared Radiation (IR), and mass spectroscopic data. Compound 2, 5, and 11 showed weak selective cytotoxic activity of 11 human cancer cell lines.

Crassifolins Q-W: Clerodane Diterpenoids From Croton crassifolius With Anti-Inflammatory and Anti-Angiogenesis Activities.

Seven new clerodane diterpenoids, crassifolins Q−W (1–7), along with five known analogues (8–12), were isolated from the roots of Croton crassifolius. Their structures were identified by comprehensive spectroscopic analysis (UV, IR, NMR, and HR-ESI-MS), and their absolute configurations were determined by ECD spectra and X-ray crystallography. The activities of compounds 1–5 against inflammatory cytokines IL-6 and TNF-α levels on LPS-induced RAW 264.7 macrophages were assessed, and compound 5 showed the most significant activity with the secretion levels of IL-6 and TNF-α at 32.78 and 12.53%, respectively. Moreover, compounds 1–5 were screened for their anti-angiogenesis using a human umbilical vein endothelial cells in vitro mode; the results showed all of them exhibited obvious anti-angiogenesis activities, in particular, compound 5 showed the strongest anti-angiogenesis effect in the range of 6.25–50 μM.

Clerodane Diterpenoids Identified from Polyalthia longifolia Showing Antifungal Activity against Plant Pathogens.

In the search for new natural resources showing plant disease control effects, we found that the methanol extract of Polyalthia longifolia suppressed fungal disease development in plants. To identify the bioactive substances, the methanol extract of P. longifolia was extracted by organic solvents, and consequently, four new 2-oxo-clerodane diterpenes (1-4), a new 4(3 → 2)-abeo-clerodane diterpene (5), together with ten known compounds (6-16) were isolated and identified from the extracts. Of the new compounds, compound 2 showed a broad spectrum of antifungal activity with moderated minimum inhibitory concentration (MIC) values in a range of 50-100 μg/mL against tested fungal pathogens. Considering with the known compounds, compound 6 showed the most potent antifungal activity with an MIC value in the range of 6.3-12.5 μg/mL. When compound 6 was evaluated for an in vivo antifungal activity against rice blast, tomato late blight, and pepper anthracnose, compound 6 reduced the plant disease by at least 60% compared to the untreated control at concentrations of 250 and 500 μg/mL. Together, our results suggested that the methanol extract of twigs and leaves of P. longifolia and its major compound 6 could be used as a source for the development of eco-friendly plant protection agents.

Neo-clerodane Diterpenoids with Hypoglycemic Effects in Vivo from the Aerial Parts of Salvia hispanica L.

A new neo-clerodane diterpenoid, salvihispin H (1), and six known ones (2-7) were identified from the aerial parts of Salvia hispanica L. The structure and absolute configuration of 1 were elucidated by extensive analysis of spectroscopic (1 H, 13 C, and 2D NMR, and HR-ESI-MS) and single-crystal X-ray diffraction data. The anti-diabetic effects of salvihispin H (1) and salvifaricin (2) were evaluated in diabetic db/db mice. The data showed that 1 and 2 could significantly reduce fasting blood glucose level and improve insulin resistance, and compound 1 exerted glucose-lowering effect more quickly than metformin. In addition, 1 and 2 could also reduce serum TG level in db/db mice. These results demonstrated that compounds 1 and 2 could be considered as potent candidates for the therapy of type 2 diabetes mellitus (T2DM).

Chemical Composition and Biological Activities of Croton delpyi, Croton decalvatusand Croton caudatus

Background: C. delpyi, C. decalvatus and C. caudatus are in the Euphorbiaceae family. The aerial parts, such as twigs, leaves and barks of these plants are used as traditional medicine such as anti-inflammatory, cytotoxicity, and antifungal properties. Objectives: The aims of this work were 1) to study the chemical composition of C. delpyi, C. decalvatus, and C. caudatus 2) to test the antibacterial, anti-HIV-1 RT, and cytotoxicity activities of crude extracts and pure compounds from these plants. Methods: Extraction, separation and purification of three plants were performed following chromatographic method. The biological activities, including antibacterial, anti-HIV-1 RT and cytotoxicity assay of three plants, were evaluated by the standard methods. Results: Phytochemical investigation of C. delpyi highlighted a new clerodane diterpenoid; crotondelpyitin A (1). The five known compounds were found, such as acetyl aleuritolic acid (2), 5- hydroxy-7,4′-dimethoxyflavone (3), and pilloin (4) in C. decalvatus and 3α-benzoyloxy-D while Afriedo- oleanan-27,16α-lactone (5), and bergenin (6) in C. caudatus. Compound 3 showed the most effective antibacterial activities with MIC in range <0.16 -1.25 mg/mL, and MBC in range 0.6 - >5.0 mg/mL. The six compounds were inactive with anti-HIV-1 RT. In addition, compound 4 was active for cytotoxic activities on FaDu and KKU-M213 at <4 μg/mL. Conclusion: The present study reveals that the Croton species are sources of diterpenoid-type compounds and a significant guide for further research of chemical constituents from these plants as potential medicines.

Dimeric clerodane diterpenoids and antiviral constituents of Dodonaea viscosa

Three unprecedented dimeric clerodane diterpenoids, dodovisdimers A−C (1–3), along with six known clerodane monomers (4–9), were isolated from Dodonaea viscosa. Compounds 1–3 may be biosynthetically formed via an intermolecular Diels-Alder [4+2] cycloaddition between the coexisting monomers 4–7. The structures of these clerodanes were characterized by spectroscopic techniques, X-ray crystallographic study, and ECD calculations. Some isolates exerted antiviral effects on human influenza A virus (H3N2) in vitro.

Clerodane and 5 10-Seco-Clerodane-type diterpenoids from Salvia involucrata

From the leaves of Salvia involucrata Cav., eight clerodane diterpenoids were isolated, of which 1−3 have not been previously described. Their structures were established by spectroscopic and spectrometric means and named as involucratin A (1), involucratin B (2), and involucratin C (3). The absolute configuration of compounds 1 and 3 was established using a combination of experimental and theoretical ECD data, whereas the one for compound 2 was determined by NOESY experiments together with ECD and DP4+ statistical analysis. Furthermore, the known clerodane compounds (5R,7R,8S,9R,10R,12R)-7-hydroxycleroda-1,3,13(16),14-tetraene-17,12;18,19-diolide (4), (‒)-hardwickiic acid (5), 1-deoxybacrispine (6), 7α-hydroxybacchotricuneatin A (7), and kingidiol (8), along with the flavonoid salvigenin, and a mixture of ursolic and oleanolic acids were also isolated. The antiproliferative activity of compounds 1‒3, 5, and 7, 8 was evaluated against a panel of cancer cell-lines (six strains) using the sulforhodamine B assay.

Flavonoids and Acid-Hydrolysis derivatives of Neo-Clerodane diterpenes from Teucrium flavum subsp. glaucum as inhibitors of the HIV-1 reverse transcriptase–associated RNase H function

Bioassay-guided fractionation of the ethyl acetate extract from Teucrium flavum subsp. glaucum, endowed with inhibitory activity towards the HIV-1 reverse transcriptase–associated RNase H function, led to the isolation of salvigenin (1), cirsimaritin (2) and cirsiliol (3) along with the neo-clerodanes teuflavin (4) and teuflavoside (5). Acid hydrolysis of the inactive teuflavoside provided three undescribed neo-clerodanes, flavuglaucins A-C (7-9) and one known neo-clerodane (10). Among all neo-clerodanes, flavuglaucin B showed the highest inhibitory activity towards RNase H function with a IC50 value of 9.1 μM. Molecular modelling and site-directed mutagenesis analysis suggested that flavuglaucin B binds into an allosteric pocket close to RNase H catalytic site. This is the first report of clerodane diterpenoids endowed with anti-reverse transcriptase activity. Neo-clerodanes represent a valid scaffold for the development of a new class of HIV-1 RNase H inhibitors.

Clerodane diterpenoids from Dodonaea viscosa and their inhibitory effects on ATP citrate lyase

Six undescribed clerodane diterpenoids, dodovisins A−F, together with nine known ones, were isolated from the aerial parts of Dodonaea viscosa (L.) Jacq. Their structures were elucidated by extensive spectroscopic techniques, X-ray crystallographic analysis, and ECD calculation. Dodovisins A and B possess a rare carbon skeleton featuring a bicyclo[6.2.0]decane motif. Dodovisins C−E represent the first clerodane diterpenoids with a 4(5 → 19)-abeo-2,4,10(1)-triene moiety. Dodovisins A, E, and strictic acid showed potent inhibitory activities against ATP citrate lyase.

Infraspecific Chemical Variability and Biological Activity of Casearia sylvestris from Different Brazilian Biomes.

Casearia sylvestris is an outstanding representative of the Casearia genus. This representability comes from its distinctive chemical profile and pharmacological properties. This species is widespread from North to South America, occurring in all Brazilian biomes. Based on their morphology, 2 varieties are recognized: C. sylvestris var. sylvestris and C. sylvestris var. lingua. Despite the existence of data about their chemical composition, a deeper understanding of the specialized metabolism correlation and variation in respect to environmental factors and its repercussion over their biological activities was still pending. In this study, an UHPLC-DAD-based metabolomics approach was employed for the investigation of the chemical variation of 12 C. sylvestris populations sampled across 4Brazilian biomes and ecotones. The correlation between infraspecific chemical variability and the cytotoxic and antioxidant activities was achieved by multivariate data analysis. The analyses showed that C. sylvestris var. lingua prevailed at Cerrado areas, and it was correlated with lower cytotoxic activity and high level of glycosylated flavonoids. Among them, narcissin and isorhamnetin-3-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranoside showed good correlation with the antioxidant activity. Conversely, C. sylvestris var. sylvestris prevailed at the Atlantic Forest areas, and it was associated with high cytotoxic activity and high content of clerodane diterpenoids. Different casearins showed good correlation (R2 = 0.3 - 0.70) with the cytotoxic activity. These findings highlighted the great complexity among different C. sylvestris populations, their chemical profile, and the related biological activities. Consequently, it can certainly influence the medicinal properties, as well as the quality and efficacy, of C. sylvestris phytomedicines.

Dolabellane and Clerodane Diterpenoids from the Twigs and Leaves of Casearia kurzii.

A pair of enantiomeric 15-nordolabellane diterpenoids, (-)- and (+)-caseadolabellols A (1a and 1b), three dolabellane diterpenoids, caseadolabellols B-D (2-4), two dolastane diterpenoids, caseadolastols A and B (5 and 6), 10 clerodane diterpenoids, caseakurzins A-J (7-16), and nine known diterpenoids (17-25) were isolated from the twigs and leaves of Casearia kurzii. The structures of the new compounds were established on the basis of extensive spectroscopic data, and those of compounds 1a, 1b, and 2 were verified by single-crystal X-ray crystallographic analysis. The enantiomers 1a and 1b were separated by chiral-phase HPLC. The absolute configurations were determined by experimental and calculated ECD data, the modified Mosher's method, or literature comparison. Compounds 1a and 5 showed significant quinone reductase-inducing activity in Hepa 1c1c7 cells, while 1b showed moderate activity. Molecular docking studies showed that 1a had greater binding affinity with Nrf2 protein (5FNQ) than 1b. The cytotoxic activity of compounds 1a, 1b, 2-12, 15, and 16 was evaluated, among which compounds 8 and 16 exhibited significant inhibitory activity against the A549 cell line. Compounds 8 and 16 induced the A549 cells to arrest at G2/M and S phases, respectively, and both compounds induced apoptosis in A549 cells.

Terpenes isolated from Polyalthia simiarum and their cytotoxic activities

Two new C31 triterpenes, polysimiaric acid A (1) and B (2) as well as one new clerodane diterpenoid, 16,16-dimethoxy-cleroda-3,13Z-dien-15-oic acid (3), together with six known compounds were isolated from Polyalthia simiarum. Their structures were determined by analysis of 1D and 2D NMR data. Three new compounds were tested for their cytotoxicity against five human tumour cell lines. Compound 3 showed cytotoxic activities against SMMC-7721 with the IC50 value of 22.43 μM.

Crotonpenoids A and B, Two Highly Modified Clerodane Diterpenoids with a Tricyclo[7.2.1.02,7]dodecane Core from Croton yanhuii: Isolation, Structural Elucidation, and Biomimetic Semisynthesis.

Crotonpenoids A (1) and B (2), two highly modified clerodane diterpenoids featuring a new 10-(butan-2-yl)-1,6,12-trimethyltricyclo[7.2.1.02,7]dodecane skeleton, were isolated from the leaves and twigs of Croton yanhuii. Their structures including the absolute configurations were determined by spectroscopic analysis, single-crystal X-ray diffraction, and biomimetic semisynthesis. Compounds 1 and 2 exhibited an agonistic effect on pregnane X receptor at 10 μM.

Diterpenoids from the leaves of Casearia kurzii showing cytotoxic activities.

A phytochemical investigation to obtain bioactive substances as lead compounds or agents for cancer led to the obtainment of six new and two known clerodane diterpenoids from the leaves of Casearia kurzii. Their structures were elucidated using NMR techniques and electronic circular dichroism (ECD) calculations. The subsequent biological cytotoxicity evaluation of these isolates toward human lung cancer A549, human cervical cancer HeLa, human chronic myeloid leukemia K562, and human hepatocellular carcinoma HepG2 was carried out. The most active compound 4 with an IC50 value of 9.7μM against HepG2 cells was selected to examine the cytotoxic mechanism, which induced the apoptosis and arrested the HepG2 cell cycle at S stage. The in vivo zebrafish experiments revealed that compound 4 had the property of inhibiting tumor proliferation and migration.