Abietane Diterpenes Research Articles

Molecular Docking Studies of Royleanone Diterpenoids from Plectranthus spp. as P-Glycoprotein Inhibitors.

The development of multidrug resistance (MDR) is a major cause of failure in cancer chemotherapy. Several abietane diterpenes with antitumoral activities have been isolated from Plectranthus spp. such as 6,7-dehydroroyleanone (DHR, 1) and 7α-acetoxy-6β-hydroxyroyleanone (AHR, 2). Several royleanone derivatives were prepared through hemisynthesis from natural compounds 1 and 2 to achieve a small library of products with enhanced anti-P-glycoprotein activity. Nonetheless, some derivatives tend to be unstable. Therefore, to reason such lack of stability, the electron density based local reactivity descriptors condensed Fukui functions and dual descriptor were calculated for several derivatives of DHR. Additionally, molecular docking and molecular dynamics studies were performed on several other derivatives to clarify the molecular mechanisms by which they may exert their inhibitory effect in P-gp activity. The analysis on local reactivity descriptors was important to understand possible degradation pathways and to guide further synthetic approaches toward new royleanone derivatives. A molecular docking study suggested that the presence of aromatic moieties increases the binding affinity of royleanone derivatives toward P-gp. It further suggests that one royleanone benzoylated derivative may act as a noncompetitive efflux modulator when bound to the M-site. The future generation of novel royleanone derivatives will involve (i) a selective modification of position C-12 with chemical moieties smaller than unsubstituted benzoyl rings and (ii) the modification of the substitution pattern of the benzoyloxy moiety at position C-6.

Insight the Biological Activities of Selected Abietane Diterpenes Isolated from Plectranthus spp.

Natural compounds isolated from plants are excellent starting points in drug design and have been widely studied as anticancer agents; they hence find use in a considerable proportion of anticancer drugs. The genus Plectranthus (Lamiaceae) comprises a large and widespread group of species with various applications in traditional medicine. Therefore, the aim of the present study was to determine the effectiveness of treatment with four abietane diterpenoids isolated from P. madagascariensis and P. ecklonii, 6,7-dehydroroyleanone, 7β,6β-dihydroxyroyleanone, 7α-acetoxy-6β-hydroxyroyleanone and parvifloron D, in initiating apoptosis in a glioma cell line. The pure compounds were found to exhibit anticancer effects in primary H7PX glioma cells line by inducing apoptosis G2/M cell cycle arrest and double-strand breaks, indicated by increased levels of phosphorylated H2A.X and decreasing mitochondrial membrane potential; they also influenced the expression of pro- and anti-apoptotic genes (Bax, Bcl-2, TP53, or Cas-3). Our findings indicate that these compounds may offer potential as beneficial antitumor drugs but further in vivo studies are needed.

Anti-inflammatory diterpenes and steroids from peels of the cultivated edible mushroom Wolfiporia cocos

Chemical investigation on the peels of the cultivated edible mushroom Wolfiporia cocos led to the identification of 13 diterpenes and 4 steroids, including two new abietane diterpenes (1 and 2) and one new pregnane steroid (14). Structures of new compounds were determined by analysis of NMR, MS, and electronic circular dichroism (ECD) data. All compounds were evaluated for cytotoxicity (K562 and HepG2), antimicrobial and anti-inflammatory activity. Compounds 15, 17 showed strong cytotoxicity on K562 cells with the IC50 values of 5.4 and 7.5 μM, respectively. Compounds 4, 9 and 17 displayed medium antibacterial activity against Staphylococcus aureus with MICs of 31.3, 48.5 and 12.5 μM, respectively. Compounds 1-10, 14 and 16 showed inhibitory activity on the NO (nitric oxide) release in LPS-induced RAW 264.7 cells with IC50 values at the range of 16.8–75.8 μM. This work confirms the potential of peels of W. cocos in the treatment of infection diseases.

Anti-MRSA activity of abietane diterpenes from Coleus blumei Benth.

Two heretofore uncharacterised abietane diterpenes, sincoetsin C (1) and 3-hydroxyspirocoleon 7-O-β-D-glucoside (4), were isolated from a methanolic extract of Coleus blumei Benth. (Lamiaceae), along with the known compounds, scutellarioidone A (2) and spirocoleon 7-O-β-D-glucoside (3) using chromatographic techniques. Their structures were determined by 1D and 2D nuclear magnetic resonance including HSQC, HMBC, COSY and NOESY experiments, mass spectrometry (HR-MS) and other spectroscopic methods (UV, IR). Their antibacterial activity against the reference strain of methicillin-resistant Staphylococcus aureus subsp. aureus CCM 4750 (MRSA) was evaluated using optical absorption to obtain quantitative information on their growth. All isolated compounds displayed anti-MRSA 4750 activity at the concentration of 512 μg/mL. Sincoetsin C (1) was the abietane diterpene most active against MRSA 4750, with a minimum inhibitory concentration of 128 μg/mL.

Inhibition of squalene synthase of rat liver by abietane diterpenes derivatives

In the current study, chemical composition of cultivated Salvia canariensis L was determined. Carnosol was the main product isolated. We prepared more lipophilic derivatives from carnosol, and both isolated and semisynthetic abietane diterpenes were evaluated in vitro as inhibitors of squalene synthase. Among the compounds tested, carnosol was the most potent inhibitor (IC50 = 17.6 μM). These results highlight the great potential of this species for the production of new ingredients in nutritional supplements for the treatment of hyperlipidemia.

Alpha-Glucosidase and Alpha-Amylase Inhibitory Activities of Novel Abietane Diterpenes from Salvia africana-lutea.

The re-investigation of a methanolic extract of Salvia africana-lutea collected from the Cape Floristic Region, South Africa (SA), afforded four new abietane diterpenes, namely 19-acetoxy-12-methoxycarnosic acid (1), 3β-acetoxy-7α-methoxyrosmanol (2), 19-acetoxy-7α-methoxyrosmanol (3), 19-acetoxy-12-methoxy carnosol (4), and two known named clinopodiolides A (5), and B (6), in addition to four known triterpenes, oleanolic, and ursolic acids (7, 8), 11,12-dehydroursolic acid lactone (9) and β-amyrin (10). The chemical structural elucidation of the isolated compounds was determined on the basis of one and two dimensional nuclear magnetic resonance (1D and 2D NMR), high-resolution mass spectrometry (HRMS), ultra violet (UV), fourier transform infrared (IR), in comparison with literature data. The in vitro bio-evaluation against alpha-glucosidase showed strong inhibitory activities of 8, 10, and 7, with the half inhibitory concentration (IC50) values of 11.3 ± 1.0, 17.1 ± 1.0 and 22.9 ± 2.0 µg/mL, respectively, while 7 demonstrated the strongest in vitro alpha-amylase inhibitory activity among the tested compounds with IC50 of 12.5 ± 0.7 µg/mL. Additionally, some of the compounds showed significant antioxidant capacities. In conclusion, the methanolic extract of S. africana-lutea is a rich source of terpenoids, especially abietane diterpenes, with strong antioxidant and anti-diabetic activities that can be helpful to modulate the redox status of the body and could therefore be an excellent candidate for the prevention of the development of diabetes, a disease where oxidase stress plays an important role.

Cytotoxic Activity of Royleanone Diterpenes from Plectranthus madagascariensis Benth.

Cytotoxicity screenings have identified Plectranthus plants as potential sources of antitumor lead compounds. In this work, several extracts from Plectranthus madagascariensis were prepared using different solvents (acetone, methanol, and supercritical CO2) and extraction techniques (maceration, ultrasound-assisted, and supercritical fluid extraction), and their chemical composition was detailed using high-performance liquid chromatography with a diode array detector. The cytotoxic activity of the major compounds identified, namely, rosmarinic acid (1) and abietane diterpenes 7α,6β-dihydroxyroyleanone (2), 7α-formyloxy-6β-hydroxyroyleanone (3), 7α-acetoxy-6β-hydroxyroyleanone (4), and coleon U (5), was evaluated in a battery of human cancer cell lines, including breast (MDA-MB-231, MCF-7), colon (HCT116), and lung (NCI-H460, NCI-H460/R) cancer, and also in healthy lung (MCR-5) cells. Royleanone (3) was isolated for the first time from P. madagascariensis, and its full spectroscopic characterization (proton and carbon nuclear magnetic resonance) was accomplished. A high selectivity for lung cancer cells was observed for royleanones (2, 4) with selectivity indexes of 4.3 and 3.2, respectively. The observed results combined with literature data allowed the establishment of important structure–activity relationships for substituted royleanone abietanes, such as the requirement for an electron-donating group at positions 6 and/or 7 in the abietane skeleton, and an improved cytotoxic effect for substituents with log P values between 2 and 5.

High Yield of Bioactive Abietane Diterpenes in Salvia sclarea Hairy Roots by Overexpressing Cyanobacterial DXS or DXR Genes.

Abietane diterpenoids, containing a quinone moiety, are synthesized in the roots of several Salvia species. Promising cytotoxicity and antiproliferative activities have been reported for these compounds in various cell and animal models. We have recently shown that aethiopinone, an o-naphto-quinone diterpene, produced in the roots of different Salvia species, is selectively cytotoxic against the A375 melanoma cell line. To enhance the synthesis of this abietane diterpenoid, we have engineered the plastidial 2-C-methyl-D-erythritol 4-phosphate-derived isoprenoid pathway in Salvia sclarea hairy roots by ectopic expression and plastid targeting of cyanobacterial genes encoding the 1-deoxy-D-xylulose 5-phosphate synthase or 1-deoxy-D-xylulose-5-phosphate reductoisomerase gene, the first two enzymatic steps of the plastidial MEP pathway, from which plant diterpenes primarily derive. Plastid-targeted expression of 1-deoxy-D-xylulose 5-phosphate synthase and 1-deoxy-D-xylulose-5-phosphate reductoisomerase proteins significantly enhanced the yield of aethiopinone by a 3-fold and about 6-fold increase, respectively. The accumulation of other abietane-type diterpenes (ferruginol, salvipisone, and carnosic acid), with interesting antiproliferative activity, was also increased. Compared to our previous data obtained by overexpressing the plant orthologous 1-deoxy-D-xylulose 5-phosphate synthase and 1-deoxy-D-xylulose-5-phosphate reductoisomerase genes in S. sclarea hairy roots, the results presented here confirm that the bacterial 1-deoxy-D-xylulose-5-phosphate reductoisomerase enzyme plays a major role than the DXS enzyme in the biosynthetic pathway of this class of compounds and that its ectopic expression does not conflict with active hairy root growth, resulting in a balanced trade-off between the transgenic hairy root final biomass and the increased content of o-naphto-quinone diterpenes, with interesting biological activities.

CYP76 Oxidation Network of Abietane Diterpenes in Lamiaceae Reconstituted in Yeast.

Rosemary and sage species from Lamiaceae contain high amounts of structurally related but diverse abietane diterpenes. A number of substances from this compound family have potential pharmacological activities and are used in the food and cosmetic industry. This has raised interest in their biosynthesis. Investigations in Rosmarinus officinalis and some sage species have uncovered two main groups of cytochrome P450 oxygenases that are involved in the oxidation of the precursor abietatriene. CYP76AHs produce ferruginol and 11-hydroxyferruginol, while CYP76AKs catalyze oxidations at the C20 position. Using a modular Golden-Gate-compatible assembly system for yeast expression, these enzymes were systematically tested either alone or in combination. A total of 14 abietane diterpenes could be detected, 8 of which have not been reported thus far. We demonstrate here that yeast is a valid system for engineering and reconstituting the abietane diterpene network, allowing for the discovery of novel compounds with potential bioactivity.

Binding of Telomeric DNA G‐Quadruplexes by Abietane Diterpene Natural Products

We have carried out studies on a homologous series of abietane diterpenes binding to a human telomeric G‐quadruplex (G4) DNA sequence [5′G3(T2AG3)3]. These G4 DNA structures are found in G‐rich telomeric regions at the ends of chromosomes and near promoter regions of oncogenes. Targeted stabilization of G‐quadruplex DNA by drugs has been implicated in telomerase inhibition and downregulation of oncogenes, both of which should result in an inhibition of cancer growth. The abietane diterpenes are a class of natural products isolated from certain plants (e.g., Hyptis verticillata) known in many cultures for their anti‐microbial, anti‐inflammatory, and anti‐cancer medicinal benefits. Binding characteristics were evaluated using circular dichroism (CD) spectroscopy, UV‐thermal denaturation, and fluorescence displacement studies. Overall, our studies show that the abietane diterpenes of this study bind to human telomeric G4 DNA, with selected compounds binding strongly. CD spectra indicate that these compounds interact with G4 DNA, either via the G4 DNA groove or by base stacking. For one compound in particular, we observed a pair of strong induced CD signals (300 – 400 nm) associated with changes in the drug environment as it binds DNA. We also observe strong positive signals around the 250 and 285 nm absorption bands of the diterpenes. These suggest the involvement of stacking interactions with the DNA bases or within the DNA grooves. Several of the abietane diterpenes bind to DNA, resulting in increased thermal stability suggesting that binding of our compounds results in G4 stabilization (ΔTm = 7°C). Thioflavin‐T (a fluorescent dye known to bind to G4 DNA) was used for fluorescent displacement studies and indicated that some diterpenes were unable to displace it from its binding site on the G4 DNA, suggesting the diterpenes occupied distinct binding sites. The binding of these abietane diterpenes to G4 DNA suggests promising therapeutic potential as lead compounds and warrants further investigation.Support or Funding InformationThis study was lead by Dr Ruel Mcknight, professor of Chemistry and Biochemistry at SUNY Geneseo.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Carnosic Acid and its Derivatives: Diterpenes of Biological Interest

Carnosic Acid (CA) and its major oxidized derivative, carnosol, are phenolic abietane diterpenes present in various species of the Lamiaceae family, such as Salvia and Rosmarinus .

Naturally Occurring Plectranthus-derived Diterpenes with Antitumoral Activities

The study of natural sources such as plants, microorganisms and marine organisms has developed interest among the scientific community in recent years for their extensive and diverse chemical composition and consequent biological potential. The search for antitumor compounds is among the lead causes that justify phytochemical studies. Although some natural products have served as FDA approved chemotherapeutic agents, there is still a demand for the search of compounds with those characteristics. The Plectranthus genus has long been used in traditional medicine, and scientific studies have already proven its undeniable value as a source of bioactive compounds. Diterpenes are the most prominent biologically active group of secondary metabolites present in this genus. In particular, abietane diterpenes have long been studied for their biological activities, namely their anti-tumoral potential. In this review, abietane diterpenes isolated from Plectranthus genus with antiproliferative, antitumoral or cytotoxic potential are reported. In addition, a correlation between this subclass of diterpenes with their mechanisms of cell death has been discussed.

Bioinspired Synthesis of Pygmaeocins and Related Rearranged Abietane Diterpenes: Synthesis of Viridoquinone.

A bioinspired synthesis of rearranged abietane diterpenes, related to pygmaeocins, is described. In this process, the key step is the 1,2-migration of the C-20 angular methyl to the C-5 position of the abietane skeleton, which occurs when a C6-C7 unsaturated dehydroabietane derivative is treated with SeO2 in dioxane under reflux (19 examples for this rearrangement are described). Utilizing this reaction, an enantiospecific synthesis of pygmaeocin C and the first synthesis of viridoquinone, starting from the abietane phenol ferruginol, are reported. A tentative mechanism for this reaction and a possible biosynthetic pathway for this family of metabolites are postulated.

Correction to: Increasing the synthesis of bioactive abietane diterpenes in Salvia sclarea hairy roots by elicited transcriptional reprogramming.

Unfortunately, the second author name was wrongly published in the original publication. The correct author name should read as follows.

Coactivation of MEP-biosynthetic genes and accumulation of abietane diterpenes in Salvia sclarea by heterologous expression of WRKY and MYC2 transcription factors

Plant abietane diterpenoids (e.g. aethiopinone, 1- oxoaethiopinone, salvipisone and ferruginol), synthesized in the roots of several Salvia spp, have antibacterial, antifungal, sedative and anti-proliferative properties. Recently we have reported that content of these compounds in S. sclarea hairy roots is strongly depending on transcriptional regulation of genes belonging to the plastidial MEP-dependent terpenoid pathway, from which they mostly derive. To boost the synthesis of this interesting class of compounds, heterologous AtWRKY18, AtWRKY40, and AtMYC2 TFs were overexpressed in S. sclarea hairy roots and proved to regulate in a coordinated manner the expression of several genes encoding enzymes of the MEP-dependent pathway, especially DXS, DXR, GGPPS and CPPS. The content of total abietane diterpenes was enhanced in all overexpressing lines, although in a variable manner due to a negative pleiotropic effect on HR growth. Interestingly, in the best performing HR lines overexpressing the AtWRKY40 TF induced a significant 4-fold increase in the final yield of aethiopinone, for which we have reported an interesting anti-proliferative activity against resistant melanoma cells. The present results are also informative and instrumental to enhance the synthesis of abietane diterpenes derived from the plastidial MEP-derived terpenoid pathway in other Salvia species.

Two new abietane diterpenes huperphlegmarins A and B from Huperzia phlegmaria

Two new abietane diterpenes, huperphlegmarin A–B (1–2), were isolated from the aerial parts of Huperzia phlegmaria (L.) Rothm. (Lycopodiaceae), in addition to five known compounds including lycoxanthol (3), 21β-hydroxyserrat-14-en-3β-yl acetate (4), 21α-hydroxyserrat-14-en-3β-yl acetate (5), 21α-hydroxyserrat-14-en-3β-ol (6), and fawcettidine (7). Their structures were determined by the combination analyses of spectroscopy, including 1D-, 2D-NMR, HRESIMS, CD and comparison with the reported data in the literature. Huperphlegmarin B (2) presented the rare 1,11-epoxy group in the molecule. Compounds 3, 4, 5 and 6 were performed for AChE inhibitory activity and compound 3 showed the inhibitory activity against AChE with IC50 of 465.6 μg/mL.

Potentiation of the anticancer effect of doxorubicinin drug-resistant gastric cancer cells by tanshinone IIA

BackgroundGastric cancer is the fifth commonest cancer and the third cause of cancer-related deaths all over the world. The effectiveness of chemotherapy is still limited by drug resistance in gastric cancer. Tanshinones, abietane diterpenes isolated from the traditional Chinese medicine Danshen (Salvia miltiorrhiza), have exhibited versatile anticancer activities in particular the ability to overcome drug resistance in different cancers. PurposeThe current study aimed to explore the capacity of tanshinone IIA, the most abundant tanshinone found in the plant Danshen, to overcome drug resistance of gastric cancer cells to a commonly used anticancer drug doxorubicin. Study designSensitivity of cell lines to doxorubicin was determined by MTT assay. Doxorubicin resistant gastric cancer cell lines was established by step selection with increasing concentrations of doxorubicin. Cell cycle arrest, apoptosis and doxorubicin efflux were analyzed by flow cytometry. The expression of MRP1 was determined by realtime PCR and western-blot. ResultsBased on the IC50 values of doxorubicin, we identified the doxorubicin-sensitive gastric cancer cell lines SNU-719 and SNU-610 as well as the cell lines relatively resistant to doxorubicin including SNU-638, SNU-668, SNU-216 and SNU-620. We also established two drug-resistant cell lines SNU-719R and SNU-610R. Despite the fact that tanshinone IIA alone showed no cytotoxicity on these gastric cells, we found the potentiation of the anticancer effect of doxorubicin in drug-resistant gastric cancer cells by tanshinone IIA. Furthermore, using doxorubicin-sensitive cell line SNU-719 and doxorubicin-resistant cell lines SNU-719R and SNU-620, we revealed the pivotal roles of MRP1. Its overexpression impaired cell cycle arrest and suppressed apoptosis in the development of both intrinsic and acquired drug resistance in gastric cancer cells to doxorubicin. Importantly, inhibition of MRP1 function enhanced cell cycle arrest, increased apoptosis and induced autophagic cell death which contributed to the capability of tanshinone IIA to potentiate the anticancer effect of doxorubicin in drug-resistant gastric cancer cells. ConclusionTanshinone IIA is an interesting agent with potential to treat drug-resistant gastric cancer in combination therapy.

P-272 - Diterpenes from Plectranthus spp.: a ROS-induced cytotoxicity study

Plants from the Plectranthus genus are commonly known for their medicinal properties, and their applications are vast in traditional medicine. Often accountable for these properties, bioactive secondary metabolites such as diterpenes are present in these plants, and some possess cytotoxic properties. Abietane diterpenes 7α-acetoxy-6β-hydroxyroyleanone, 7β,6β-dihydroxyroyleanone, 6,7- dehydroroyleanone, and parvifloron D are examples of such class of bioactive diterpenes. These abietanes are obtained from Plectranthus genus plants as their major compounds. In this work, the cytotoxic properties of these abietanes have been studied. This property was evaluated through MTT assays on A549 cells and CCRF-CEM cells. In addition, the level of intracellular Reactive Oxygen Species (ROS) in these cells was also measured. Our study has revealed that on CCRF-CEM cells, there is a slight increase of the ROS levels after exposure to all compounds. Nevertheless, on A549 cells the levels of ROS increase approximately 10-fold, with notorious increase after exposure to 7β,6β-dihydroxyroyleanone, which can induce cytotoxicity due to ROS accumulation on cells. In conclusion, this study proves the therapeutic potential of Plectranthus-derived diterpenes and validates its use in traditional medicine.

Chemical and Bioactivity Studies on Salvia Africana-Lutea: Cytotoxicity and Apoptosis Induction by Abietane Diterpenes Isolated from Salvia Africana-Lutea

Chemical and Bioactivity Studies on Salvia Africana-Lutea: Cytotoxicity and Apoptosis Induction by Abietane Diterpenes Isolated from Salvia Africana-Lutea

Abietane diterpenoids from Sideritis montana L. and their antiproliferative activity

The present study aimed at the phytochemical and pharmacological investigation of Sideritis montana L. (Lamiaceae). Two new abietane diterpenes [sideritins A (1) and B (2)] were isolated from the methanol extract of the plant. Six known compounds [pomiferin E (3), 9α,13α-epi-dioxyabiet-8(14)-en-18-ol (4), paulownin (5), 6-methoxysakuranetin (6), 3-oxo-α-ionol (7) and 4-allyl-2,6-dimethoxyphenol glucoside (8)] were also obtained from the plant. The structures were determined by means of HREIMS and NMR experiments. The antiproliferative effect of the isolated compounds was investigated on human cancer cell lines (HeLa, SiHa and C33A) at 10 and 30μM concentrations, using the MTT assay. The results demonstrated that pomiferin E (3) and 6-methoxysakuranetin (6) displayed considerable activity [inhibition (%)±SEM: 46.93±2.35 on HeLa (pomiferin E), and 51.52±2.45 on C33A (6-methoxysakuranetin)] at 30μM concentration.