Diterpene Derivatives Research Articles

Novel Abietane Type Sugar Triazole Hybrids and Amides against SARS‐CoV‐2 Spike Glycoprotein and Influenza A Virus

AbstractAbietane type diterpenic (dehydroabietic, 2,3‐dihydroquinopimaric and maleopimaric) acids were converted by the acid chloride method into a series of aliphatic and heterocyclic amine spacered conjugates. A number of structurally novel derivatives holding 1,2,3‐triazole moieties were designed and synthesized by treating of the propargylated amides and esters with a sugar azides using the Cu(I)‐catalyzed click chemistry approach. The synthesized N‐containing diterpene derivatives were tested for their potential inhibition of influenza A/PuertoRico/8/34 (H1N1) virus in MDCK cell culture and SARS‐CoV‐2 pseudovirus in BHK‐21‐hACE2 cells. Among tested forty‐five compounds ten derivatives were the most efficacious against influenza virus A with IC50 0.7–63.4 μM together with high selectivity index SI value from 11 from 94. Dihydroquinopimaric acid N‐ethylpiperazine‐amide and dehydroabietic acid 1,2,3‐triazoles spacered with glucose and lactose showed anti‐SARS‐CoV‐2 pseudovirus activity with EC50 values of 1.79–25.46 μM. Molecular docking and dynamics modeling investigated the binding mode of the lead compounds into the binding pocket of influenza A virus M2 protein and the RBD domain of SARS‐CoV‐2 spike glycoprotein.

Phytogenic effects of Marrubium vulgare on the growth performance of weaned piglets: biochemical parameters and liquid chromatographic-electrospray ionization-mass spectrometric profile of plant and animal serum.

Multidrug-resistant bacteria in humans have prompted the search for alternative solutions derived from herbal medicines that can substitute antibiotics in livestock production. Thus, the goal of this study was to evaluate the phytogenic properties of Marrubium vulgare infusion (MVI) on weaned pigs. Thirty animals were randomly divided into five groups of six animals, each receiving a physiological solution, clenbuterol and the infusion extract at doses of 0.01 (MVI 1%), 0.1 (MVI 10%) and 0.2 (MVI 20%) mg kg-1 for 28 days. Biochemical parameters and the liquid chromatographic-electrospray ionization-mass spectrometric (LC-ESI-MS) chemical profiles of the infusion extract and animal serum were studied. The doses MVI 1 and 10% led to weight gain higher than the controls. No significant changes were noted in the biochemical parameters including erythrocytes, hemoglobin, hematocrit, mean corpuscular volume and others. Evaluation of enzymatic levels in blood revealed no significant changes. LC-ESI-MS data of MVI showed the presence of 34 secondary metabolites, and successive chromatographic purification of MVI yielded marrubiin and apigenin as major components. LC-ESI-MS data of animal serum showed the presence of a diterpene, a flavonoid and diverse cholic acid derivatives. Results indicated the doses MVI 1 and 10% promote weight gain with no significant alterations in blood biochemicals, and liver and kidney function. © 2024 Society of Chemical Industry.

Synthesis and bioevaluation of water-soluble β-cyclodextrin-diterpene acid conjugates.

A series of β-cyclodextrin (β-CD)-conjugates were prepared by combining three abietane-type diterpene acids with two azide-functionalized β-CDs via click chemistry, and the antiviral activity against wild-type and omicron SARS-CoV-2 spike pseudovirus as well as the antibacterial activity against Escherichia coli were investigated. All the synthesised conjugates exhibited no significant cytotoxicity to BHK-21-hACE2 cells with cell viability over 80% at concentration of 15 µM. Among the conjugates, the heptavalent β-CD-dehydroabietic acid conjugate 6b exhibited higher anti-SARS-CoV-2 activity against the omicron variant compared to the other conjugates. This study suggested that the multivalent diterpene acid derivatives may have potential application against coronaviruses as entry inhibitors.

The mechanism of action underlying antibacterial activity of a diterpene quinone derivative against Staphylococcus aureus through the in vitro and in silico assays

Background: The need for new antibacterials to combat resistance is still constrained by the availability of antibacterials that are safe to use. Diterpene quinone-derived compounds are proven to have antibacterial activity. However, their mechanism of action is unknown. Objective: This study aims to determine the mechanism of antibacterial action of a diterpene quinone (6O7AR) on Staphylococcus aureus through in vitro and in silico assays. Method: MIC tests were performed using microdilution, and MBC determinations were carried out on MHA media. In vitro assays were conducted using membrane permeabilizing with Tris, Triton X-100, and ATPase-inhibiting agents with NaN3. Docking was performed on 2XCT proteins in S. aureus bacteria using AutoDock Vina. Result: The MIC and MBC results of 6O7AR were 300 μM and 2400 μM, respectively. The in vitro assay result suggested that the antimicrobial activities of 6O7AR were associated with the inhibition of ATPase function and disrupting membrane function. The docking results showed that the compound possessed good interactions with the 2XCT proteins of S. aureus. Conclusion: 6O7AR exhibited good antibacterial activity. Based on in vitro and in silico assays, the mechanism of action of this compound is related to the disruption of bacterial membrane function, and it has the potential to inhibit the ATPase enzyme and the S. aureus gyrase.

New clerodane diterpenoids from Callicarpa pseudorubella and their antitumor proliferative activity

Six previously undescribed clerodane diterpenes, cardorubellas A-F (1-6), along with seven known ones (7-13), were isolated from the aerial parts of Callicarpa pseudorubella. Their chemical structures were established by analysis of 1D and 2D NMR, HR-ESI-MS, X-ray diffraction, and electronic circular dichroism (ECD) data. Notably, cardorubella B (2) represented the first examples of naturally occurring succinic anhydride-containing clerodane diterpenes derivatives. The anti-proliferative activities of these compounds were assessed. Remarkably, compound 2 exhibited comparable inhibitory activity against HEL cell lines, surpassing the positive control with an IC50 value of 14.01 ± 0.77 μM, compared to 17.02 ± 4.70 μM for 5-fluorouracil.

Modification of a natural diterpene and its antitumor mechanism: Promoting apoptosis, suppressing migration, and inhibiting angiogenesis

The synthesis or derivation of a series of structural analogues based on natural products is a common strategy for discovering antitumor drugs. As a unique natural diterpene derived from Trigonostemon howii, 3,4-seco-sonderianol (1) exhibited moderate cytotoxic effects. To improve the activity, a new diterpene derivative (1b) with a mitochondrial targeting function was synthesized by coupling triphenylphosphine to compound 1. Compared to the parent molecule, the antitumor activity of 1b increased greatly. A series of mechanistic experiments revealed that compound 1b induced cancer cell apoptosis and inhibited cancer cell migration by targeting the mitochondria and regulating the STAT3 and FAK signaling pathways. Meanwhile, 1b was found to inhibit angiogenesis in a transgenic zebrafish model. It is worth noting that 1b also demonstrated excellent antitumor effects in zebrafish tumor xenotransplantation models. All the evidence supports that compound 1b targeting mitochondria has the potential to be a candidate for an antitumor drug.

New diterpene lactone derivatives from Aphanamixis polystachya leaves inhibit nitric oxide production in RAW 264.7 cells.

Phytochemical studies on Aphanamixis plants have attracted considerable attention over the past few decades due to the structural diversities and significant biological activities of terpenoids produced by these plants. In the present study, five new acyclic diterpene lactone derivatives, aphanamixionolides A-E (1-5), and three known tirucallane-type triterpenes, namely, piscidinol A (6), hispidone (7), and bourjotinolone A (8), were isolated from the leaves of Aphanamixis polystachya. Their structures were elucidated by comprehensive analyses of HR-ESI-MS and NMR spectroscopic data and by comparison with those reported in the literature. Absolute configurations of the new compounds were determined by experimental and TD-DFT calculated ECD spectra. Compounds 1-8 inhibited NO production with IC50 values of 10.2-37.7 μM, which are comparable to positive control l-NMMA (IC50: 31.5 μM).

Synthesized diterpene lactone derivative attenuated Freund's complete adjuvant-induced arthritis in Wistar rats.

In this study, the SP-38 (Diterpene Lactone derivative) was designed, synthesized from clerodane diterpene (lactone) isolated from Polyanthia longifolia var. pendula, and tested for anti-arthritic activity using the FCA-induced arthritic rat model. This study examined the in vivo effects of SP-38 using three different doses (20, 10, and 5 mg/kg) by oral administration for 21 days from day 8 after 0.1 ml FCA sub-planter injection until day 28. Arthritis index, paw swelling, ankle diameter, body weight as well as biochemical, hematological, histopathological, and radiological parameters were examined. Administered SP-38 reduced arthritis index, paw volume, and joint swelling compared to the arthritic control group. Accordingly, rats treated with SP-38 showed a remarkable increase in body weight and improved biochemical, hematological, histopathological, and radiological parameters. Furthermore, it reduced the increased production of CRP and RF while simultaneously decreasing ESR in all SP-38-treated rats. However, SP-38 showed promising liver protection by reducing elevated serum levels of liver and kidney function markers SGOT, SGPT, and ALP. Furthermore, splenic index, TNF-α, and IL-6 levels were significantly reduced compared to arthritic control rats at certain doses. The result of the present study concludes that SP-38 has significant anti-arthritic potential in FCA-induced arthritis in Wistar rats. SP-38 therefore showed promising anti-arthritic activity, as evidenced by attenuation of inflammation, inflammatory markers, and pro-inflammatory cytokine levels.

Extending the Structural Diversity of Labdane Diterpenoids from Marine-Derived Fungus Talaromyces sp. HDN151403 Using Heterologous Expression.

Heterologous biosynthesis has become an effective means to activate fungal silent biosynthetic gene clusters (BGCs) and efficiently utilize fungal genetic resources. Herein, thirteen labdane diterpene derivatives, including five undescribed ones named talarobicins A-E (3-7), were discovered via heterologous expression of a silent BGC (labd) in Aspergillus nidulans. Their structures with absolute configurations were elucidated using extensive MS and NMR spectroscopic methods, as well as electronic circular dichroism (ECD) calculations. These labdanes belong to four skeleton types, and talarobicin B (4) is the first 3,18-dinor-2,3:4,18-diseco-labdane diterpene with the cleavage of the C2-C3 bond in ring A and the decarboxylation at C-3 and C-18. Talarobicin B (4) represents the key intermediate in the biosynthesis of penioxalicin and compound 13. The combinatorial heterologous expression and feeding experiments revealed that the cytochrome P450 enzymes LabdC, LabdE, and LabdF were responsible for catalyzing various chemical reactions, such as oxidation, decarboxylation, and methylation. All of the compounds are noncytotoxic, and compounds 2 and 8 displayed inhibitory effects against methicillin-resistant coagulase-negative staphylococci (MRCNS) and Bacillus cereus.

Structural and functional investigations of syn-copalyl diphosphate synthase from Oryza sativa

The large superfamily of labdane-related diterpenoids is defined by the cyclization of linear geranylgeranyl pyrophosphate (GGPP), catalyzed by copalyl diphosphate synthases (CPSs) to form the basic decalin core, the copalyl diphosphates (CPPs). Three stereochemically distinct CPPs have been found in plants, namely (+)-CPP, ent-CPP and syn-CPP. Here, we used X-ray crystallography and cryo-EM methods to describe different oligomeric structures of a syn-copalyl diphosphate synthase from Oryza sativa (OsCyc1), and provided a cryo-EM structure of OsCyc1D367A mutant in complex with the substrate GGPP. Further analysis showed that tetramers are the dominant form of OsCyc1 in solution and are not necessary for enzyme activity in vitro. Through rational design, we identified an OsCyc1 mutant that can generate ent-CPP in addition to syn-CPP. Our work provides a structural and mechanistic basis for comparing different CPSs and paves the way for further enzyme design to obtain diterpene derivatives with specific chirality.

Cytotoxic Indole Diterpenoids from a Sphagneticola trilobata-Derived Fungus Aspergillus sp. PQJ-1.

Two new indole diterpene derivatives, 5S-hydroxy-β-aflatrem (1) and 14R-hydroxy-β-aflatrem (2), along with one known analogue, 14-(N,N-dimethl-L-valyloxy)paspalinine (3), were isolated from the fermentation broth of the fungus Aspergillus sp. PQJ-1 derived from Sphagneticola trilobata. The structures of the new compounds were elucidated from spectroscopic data and ECD spectroscopic analyses. All the compounds (1-3) were evaluated for their cytotoxicity against A549, Hela, Hep G2, and MCF-7 cell lines. Compounds 1 and 2 exhibited selective inhibition against Hela cells. Further studies showed that 1 significantly induced apoptosis and suppressed migration and invasion in Hela cells. Moreover, 1 could up-regulate pro-apoptotic genes BAX and Caspase-3 and down-regulate anti-apoptotic genes Bcl-xL and XIXP.

Inhibitory properties of quinopimaric acid derivatives towards cholinesterases

A series of new diterpene quinopimaric acid derivatives modified at the hydroxyl group with different pharmacophore fragments has been synthesised and their (along with previously obtained compounds) inhibitory properties towards cholinesterases were studied. Thereby an indole-3-acetyl derivative 7 and a propargyl substituted compound 28 were shown to be excellent and acetylcholinesterase-selective inhibitors. Both compounds inhibited the enzyme as a mixed type inhibitor, and Ki values of 0.41 and 0.44 µM and Ki’ values of 0.98 and 2.26 µM were determined. The binding interactions between all active compounds and ligands protein were confirmed through molecular docking study.

In-silico Screening of Novel Diterpene Derivatives for their Inhibitory Potentials against MurA Enzyme of Uropathogenic Escherichia coli

background: Enzyme UDP-NAG enolpyruvyl transferase (MurA), which aids in the formation of cell walls and is identified as the primary target of the antibiotic Fosfomycin, is a significant pharmacological target in the case of uropathogenic Escherichia coli (UPEC). Finding a potent drug with a distinct mode of action is required since UPEC treatment is challenging due to resistance and resurrection. methods: Here we have used virtual high-throughput screening and molecular dynamics simulation approach to explore the effectiveness of selected novel Diterpene derivatives against the therapeutic target MurA (both wild type and Cys115Asp mutant, which is responsible for lower effectiveness of Fosfomycin). results: The investigation showed improved binding efficacy of the ligands around the primary active site residue Cys115 as well as enhanced activity against Cys115Asp mutant. Against wildtype receptors, the docking score of best-docked diterpene derivative, DIT1 (-26.18) was found to be much better than that of the known drug, Fosfomycin (-23.72). There were 7 nos of hydrogen bonds formed by DIT1 and 5 nos by Fosfomycin, indicating a stronger interaction of DIT1 with MurA. The mutant form also showed similar findings, suggesting that DIT1 is much more effective than Fosfomycin. conclusion: The above result justifies the potential of Diterpene derivatives in blocking the MurA active site that can prevent peptidoglycan biosynthesis. Effectiveness of DIT1 against wild type as well as Cys115Asp mutant justifies that the selected ligands can be used as suitable drug candidates against MurA to add new molecules in the treatment pipeline. This establishes innovative frameworks for the creation of strong drugs that target MurA after suitable in-vitro and in-vivo trials.

Phytochemical Investigation of Lepionurus sylvestris Blume and Their Anti-Diabetes Effects via Anti-Alpha Glucosidase and Insulin Secretagogue Activities Plus Molecular Docking.

This study presents a phytochemical investigation of Lepionurus sylvestris leaf extracts and their anti-diabetic activities. Traditionally, L. sylvestris leaves were used as vegetables and food in local recipes, but the root extracts of the plant can also be used in body tonic and erectile dysfunction treatments. Following a preliminary anti-diabetic activity screening test, the 80% ethanolic leaf extract exhibited potent anti-alpha glucosidase activity. So, the leaves' active components were selected for further investigation. Firstly, the plant was extracted via maceration using lower to higher polarity solvents such as hexane, ethyl acetate, ethanol, and water, respectively, to obtain the four crude extracts. Then, the phytochemicals contained in this plant were investigated via classical column chromatography and spectroscopy techniques. Anti-diabetic activity was evaluated via anti-alpha glucosidase and insulin secretagogue assays. The results showed that five compounds were isolated from the fractionated ethanolic leaf extract: interruptin A; interruptin C; ergosterol; diglycerol; and 15-16-epoxy-neo-cleoda-3,7(20),13(16),14-tetraene-12,17:18,19-diolide, a new diterpene derivative which is herein referred to as lepionurodiolide. Interruptin A and the new diterpene derivative exhibited the greatest effect on anti-alpha glucosidase activity, showing IC50 values of 293.05 and 203.71 μg/mL, respectively. Then, molecular docking was used to study the sites of action of these compounds. The results showed that interruptin A and the new compound interacted through H-bonds with the GLN279 residue, with a binding energy of -9.8 kcal/mol, whereas interruptin A and C interacted with HIS280 and ARG315 a with binding energy of -10.2 kcal/mol. Moreover, the extracts were investigated for their toxicity toward human cancer cells, and a zebrafish embryonic toxicity model was used to determine herbal drug safety. The results indicated that ethyl acetate and hexane extracts showed cytotoxicity to both Hela cells and human breast adenocarcinomas (MCF-7), which was related to the results derived from using the zebrafish embryonic toxicity model. The hexane and ethyl acetate presented LC50 values of 33.25 and 36.55 μg/mL, respectively, whereas the ethanol and water extracts did not show embryonic toxicity. This study is the first of its kind to report on the chemical constituents and anti-diabetic activity of L. sylvestris, the leaf extract of which has been traditionally used in southern Thailand as a herbal medicine and food ingredient.

Isoryanodane diterpene derivatives from Barringtonia macrocarpa

From the MeOH residue of Barringtonia macrocarpa branches and leaves, one new isoryanodane diterpene, barringisol (1), and two new isoryanodane diterpene glucosides, barringisosides A and B (2 and 3), were obtained using various chromatographic isolations. The structural characterization was confirmed by spectroscopic methods including 1D, 2D NMR and HR-ESI-QTOF-MS. This is the first isolation of isoryanodane diterpene derivatives from Barringtonia species. Moreover, the in vitro cytotoxicity of 1−3 on three human cancer cell lines (HepG2, LNCaP and MCF7) was also accessed using SRB assays.

Antiviral effect of natural and semisynthetic diterpenoids against adenovirus infection in vitro.

The emergence and re-emergence of viruses has highlighted the need to develop new broad spectrum antivirals to mitigate human infections. Pursuing our search for new bioactive plant-derived molecules, we studied several diterpene derivatives synthesized from jatropholones A and B and carnosic acid isolated from Jatropha isabellei and Rosmarinus officinalis, respectively. Here, we investigated the antiviral effect of the diterpenes against human adenovirus (HAdV-5) that causes several infections for which there is no approved antiviral therapy yet. Ten compounds were evaluated and none of them presented cytotoxicity in A549 cells. Only compounds 2, 5 and 9 inhibited HAdV-5 replication in a concentration-dependent manner, without virucidal activity, whereas the antiviral action took place after virus internalization. The expression of viral proteins E1A and Hexon was strongly inhibited by compounds 2 and 5 and, in a lesser degree, by compound 9. Since compounds 2, 5 and 9 prevent ERK activation, they might exert their antiviral action by interfering host cell functions required for virus replication. Besides, the compounds had an anti-inflammatory profile since they significantly inhibited the levels of IL-6 and IL-8 produced by THP-1 cells infected with HAdV-5 or with an adenoviral vector. In conclusion, diterpenes 2, 5 and 9 not only exerted antiviral activity against adenovirus but also are able to restrain pro-inflammatory cytokines induced by the virus.

Discovery of myrsinane-type Euphorbia diterpene derivatives through a skeleton conversion strategy from lathyrane diterpene for the treatment of Alzheimer's disease

A series of novel myrsinane-type Euphorbia diterpene derivatives (1–37) were synthesized from the abundant natural lathyrane-type Euphorbia factor L3, using a multi-step chemical process guided by a bioinspired skeleton conversion strategy, with the aim of discovering potential anti-Alzheimer's disease (AD) bioactive lead compounds. The synthesis process involved a concise reductive olefin coupling reaction through an intramolecular Michael addition with a free radical, followed by a visible-light-triggered regioselective cyclopropane ring-opening. The cholinesterase inhibitory and neuroprotective activities of the synthesized myrsinane derivatives were evaluated. Most of the compounds showed moderate to strong potency, highlighting the importance of ester groups in Euphorbia diterpene. In particular, derivative 37 displayed the most potent acetylcholinesterase (AChE) inhibition, with an IC50 value of 8.3 μM, surpassing that of the positive control, tacrine. Additionally, 37 also showed excellent neuroprotective effect against H2O2-induced injury in SH-SY5Y cells, with a cell viability rate of 124.2% at 50 μM, which was significantly higher than that of the model group (viability rate 52.1%). Molecular docking, reactive oxygen species (ROS) analysis, immunofluorescence, and immunoblotting were performed to investigate the mechanism of action of myrsinane derivative 37. The results indicated that derivative 37 may be a promising myrsinane-type multi-functional lead compound for the treatment of Alzheimer's disease. Furthermore, a preliminary SAR analysis was performed to study the acetylcholinesterase inhibitory and neuroprotective activities of these diterpenes.

Diterpene and biflavone derivatives from Thuja koraiensis and their cytotoxicities against A549 cells

During the screening of the cytotoxicity of rare Korean endemic plants, the extract of Thuja koraiensis Nakai displayed potent cytotoxicity against the adenocarcinomic human alveolar basal epithelial A549 cell line. Through a series of separations via column chromatography, three undescribed abietanes, an undescribed labdane along with a labdane, and a biflavonoid were purified from methylene chloride (CH2Cl2) fraction possessing a potent cytotoxic effect. Extensive 1D and 2D NMR spectroscopic data analyses, in combination with quantum chemical calculations were conducted to establish the planar and absolute configurations of thujakoraienes A–C. The chemical structure of thujakoraiene D was elucidated by spectroscopic data analysis and competing enantioselective acylation. Thujakoraienes A and C along with 7,7″-di-O-methylamentoflavone, showed cytotoxic effects on A549 cells, with IC50 values of 64.86, 47.97, and 16.14 μM, respectively. Finally, thujakoraiene C and 7,7″-di-O-methylamentoflavone were identified as potent cytotoxic compounds in A549 cells, followed by an additional cytotoxicity test in the normal human lung fibroblast MRC-5 cell line. This is the first study on the non-volatile chemicals in the extract of T. koraiensis and comparison of chemical profiles of T. orientalis and T. koraiensis.

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-3β) 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.

Abietic, maleopimaric and quinopimaric dipeptide Ugi-4CR derivatives and their potency against influenza A and SARS-CoV-2

A set of 12 abietane diterpene derivatives have been synthesised by the Ugi-four component reaction (Ugi-4CR) and tested for cytotoxicity and activity against influenza virus A/Puerto Rico/8/34 (H1N1) and SARS-CoV-2 pseudovirus. Five dipeptide derivatives demonstrated a selectivity index (SI) higher than 10 and IC50 values from 2 to 32 μM against influenza virus. Compound 11 was found to be a lead with SI of 200, and time-of-addition experiments showed the viral entry into the cell and the binding of the virus to the receptor as a possible target. Compound 7 was the only one showed weak anti-SARS-CoV-2 activity with EC50 value of 80.96 µM. Taken together, our data suggest the potency of diterpene acids-Ugi products as new effective anti-influenza compounds.