Anti-Coxsackie virus B diterpenes from the roots of Illicium jiadifengpi

The activities of suaveolol and other compounds from Hyptis suaveolens and Momordica charantia against the aetiological agents of African trypanosomiasis, leishmaniasis and malaria

African trypanosomiasis and malaria are among the most severe health challenges to humans and livestock in Africa and new drugs are needed. Leaves of Hyptis suaveolens Kuntze (Lamiaceae) and Momordica charantia L. (Cucurbitaceae) were extracted with hexane, ethyl acetate, and then methanol, and subjected to silica gel column chromatography. Structures of six isolated compounds were elucidated through NMR and HR-EIMS spectrometry. Callistrisic acid, dehydroabietinol, suaveolic acid, suaveolol, and a mixture of suaveolol and suaveolic acid (SSA) were obtained from H. suaveolens, while karavilagenin D and momordicin I acetate were obtained from M. charantia. The isolated biomolecules were tested against trypomastigotes of Trypanosoma brucei brucei and T. congolense, and against Plasmodium falciparum. The most promising EC50 values were obtained for the purified suaveolol fraction, at 2.71 ± 0.36 μg/mL, and SSA, exhibiting an EC50 of 1.56 ± 0.17 μg/mL against T. b. brucei trypomastigotes. Suaveolic acid had low activity against T. b. brucei but displayed moderate activity against T. congolense trypomastigotes at 11.1 ± 0.5 μg/mL. Suaveolol and SSA were also tested against T. evansi, T. equiperdum, Leishmania major and L. mexicana but the antileishmanial activity was low. Neither of the active compounds, nor the mixture of the two, displayed any cytotoxic effect on human foreskin fibroblast (HFF) cells at even the highest concentration tested, being 200 μg/mL. We conclude that suaveolol and its mixture possessed significant and selective trypanocidal activity.

Five undescribed abietane-type diterpenes of Callicarpa macrophylla

A phytochemical investigation of the medicinal plant Callicarpa macrophylla resulted in the characterization of two rare rearrangement abietane-type diterpenoids, macrophypene F-G (1-2), and three abietane diterpenoids, named macrophypene H-J (3-5). Additionally, five known diterpenoids (6-10) were identified. The structures of the newly discovered compounds were fully established through extensive analysis of HRESIMS, 1D and 2D NMR data. The absolute configurations of the isolated compounds were determined using CD comparison, chemical methods, and X-ray crystal diffraction experiments. Subsequently, all isolated diterpenoids were evaluated for their inhibitory effects on extracellular PCSK9 protein levels by PCSK9 AlphaLISA screening. Jiadfenoic acid B (6, 56.80% inhibition at 20 μM) and holophyllin F (10, 43.18% inhibition at 20 μM) significantly decreased PCSK9 protein levels in medium of HepG2 cells.

Anticoronavirus Evaluation of Antimicrobial Diterpenoids: Application of New Ferruginol Analogues

The abietane diterpene (+)-ferruginol (1), like other natural and semisynthetic abietanes, is distinguished for its interesting pharmacological properties such as antimicrobial activity, including antiviral. In this study, selected C18-functionalized semisynthetic abietanes prepared from the commercially available (+)-dehydroabietylamine or methyl dehydroabietate were tested in vitro against human coronavirus 229E (HCoV-229E). As a result, a new ferruginol analogue caused a relevant reduction in virus titer as well as the inhibition of a cytopathic effect. A toxicity prediction based on in silico analysis was also performed as well as an estimation of bioavailability. This work demonstrates the antimicrobial and specifically antiviral activity of two tested compounds, making these molecules interesting for the development of new antivirals.

Effect of Modified Levopimaric Acid Diene Adducts on Mitochondrial and Liposome Membranes

This paper demonstrates the membranotropic effect of modified levopimaric acid diene adducts on liver mitochondria and lecithin liposomes. We found that the derivatives dose-dependently reduced the efficiency of oxidative phosphorylation of mitochondria due to inhibition of the activity of complexes III and IV of the respiratory chain and protonophore action. This was accompanied by a decrease in the membrane potential in the case of organelle energization both by glutamate/malate (complex I substrates) and succinate (complex II substrate). Compounds 1 and 2 reduced the generation of H₂O₂ by mitochondria, while compound 3 exhibited a pronounced antioxidant effect on glutamate/malate-driven respiration and, on the other hand, caused ROS overproduction when organelles are energized with succinate. All tested compounds exhibited surface-active properties, reducing the fluidity of mitochondrial membranes and contributing to nonspecific permeabilization of the lipid bilayer of mitochondrial membranes and swelling of the organelles. Modified levopimaric acid diene adducts also induced nonspecific permeabilization of unilamellar lecithin liposomes, which confirmed their membranotropic properties. We discuss the mechanisms of action of the tested compounds on the mitochondrial OXPHOS system and the state of the lipid bilayer of membranes, as well as the prospects for the use of new modified levopimaric acid diene adducts in medicine.

Abietane-Type Diterpenoids From Nepeta bracteata Benth. and Their Anti-Inflammatory Activity

Terpenes possess a wide range of structural features and pharmaceutical activities and are promising for drug candidates. With the aim to find bioactive terpene molecules, eight new compounds were isolated from the medicinal plant Nepeta bracteata Benth., including seven new abietane-type diterpenoids (1–7), along with a new ursane-type triterpenoid(8). The structures of compounds 1–8 were elucidated through the detailed spectroscopic analyses of their 1D and 2D NMR and MS data, and the absolute configurations of compounds 1–7 were determined by comparing their experimental and calculated ECD spectra. Compound 1 was a novel degraded carbon diterpene with the disappearing of methyl signal at C-19, while compound 7 possessed a new norabietane-type diterpenoid carbon skeleton with the presence of five-membered lactone arising from ring rearrangement. The anti-inflammatory of all obtained isolates were evaluated on lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and the results of anti-inflammatory activity screening showed that compared with the LPS model group, all compounds were significantly down-regulation the TNF-α inflammatory factor at the specific concentration, except for compound 6.

Characterization of undescribed melanoma inhibitors from Euphorbia mauritanica L. cultivated in Egypt targeting BRAFV600E and MEK 1 kinases via in-silico study and ADME prediction

Three undescribed diterpenes including two ent-abietanes, euphomauritanol A, and euphomauritanol B, and one jatrophane, euphomauritanophane A, in addition to eight previously described metabolites were isolated from the MeOH-CH₂Cl₂ (1:1) extract of the Euphorbia mauritanica. The chemical structures of isolates were established based on the spectroscopic means including FT-IR, HRMS, 1D and 2D NMR. The absolute stereochemistry of the undescribed diterpenes was deduced by experimental and calculated TDDFT-electronic circular dichroism (ECD). The anti-proliferative effects of the isolated diterpenes were evaluated against B16-BL6, Hep G2, and Caco-2. The euphomauritanol A, euphomauritanol B, and euphomauritanophane A significantly inhibited the growth of murine melanoma B16-BL6 cell lines with IC₅₀ 10.28, 20.22, and 38.81 μM, respectively with no responses against the other cells. These activities were rationalized by molecular docking of the active compounds in BRAF^V600E and MEK1 active sites. Moreover, the in-silico pharmacokinetics predictions by Swiss ADME revealed that the active compounds possessed favorable oral bioavailability and drug-likeness properties.

Inflammatory and Cytotoxic Activities of Abietane Terpenoids from Nepeta bracteata Benth

Nepeta bracteata Benth. is used clinically to treat tracheal inflammation, coughs, asthma, colds, fevers, adverse urination, and other symptoms, along with functions in clearing heat and removing dampness. However, there have been few studies characterizing the material basis of its efficacy. Therefore, the aim of this study was to screen for compounds with anti-inflammatory activities in N. bracteata Benth. Using silica gel, ODS C18, and Sephadex LH-20 column chromatography, as well as semipreparative HPLC, 10 compounds were separated from N. bracteata Benth. extract, including four new diterpenoids (1–4), one amide alkaloid (5), and five known diterpenoids (6–10). The structures of all the isolates were elucidated by HR-ESI-MS, NMR, and CD analyses. Using lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, we investigated the anti-inflammatory activities of compounds 1–10. It is worth noting that all were able to inhibit nitric oxide (NO) production with IC₅₀ values < 50 μM and little effect on RAW 264.7 macrophage viability. Compounds 2 and 4 displayed remarkable inhibition with IC₅₀ values of 19.2 and 18.8 μM, respectively. Meanwhile, screening on HCT-8 cells demonstrated that compounds 2 and 4 also had moderate cytotoxic activities with IC₅₀ values of 36.3 and 41.4 μM, respectively, which is related to their anti-inflammatory effects.

Potential of diterpene compounds as antivirals, a review

Viruses cause widely transmitted diseases resulting in pandemic conditions. Currently, the world is being hit by the Covid-19 pandemic caused by the SAR-CoV-2 infection. Countries in the world are competing to develop antivirals to overcome this problem. Diterpene compounds derived from natural ingredients (plants, corals, algae, fungi, sponges) and synthesized products have potential as antivirals. This article summarizes the different types of diterpenes such as daphnane, tiglilane, kaurane, abietane, pimarane, labdane, dollabelane, jatrophane, dolastane, prenylated guaiane, tonantzitlolone, casbane, have antivirals activity such as targeting HIV, Coxsackie virus, herpes virus, hepatitis virus, influenza virus, Chikungunya virus, Zika virus, dengue virus, and SARS-CoV. Some compounds such as andrographolide and its derivatives show promising activity in inhibiting the influenza virus. Additionally, compounds such as pineolidic acid, forskolin, sugiol, and many other diterpene compounds showed anti-SAR-CoV activity. The diterpene compound class's high antivirals potential does not rule out the possibility that these compounds can also act as anti-SAR-CoV-2 drugs in the future.

Diterpenoids with Aromatase Inhibitory Activity from the Rhizomes of Kaempferia elegans

Investigation of bioactive compounds from the rhizomes of Kaempferia elegans led to the isolation and characterization of ten new diterpenoids, namely, five 12,13-seco-diterpenoids named elegansins A-E (1-5) and five new abietanes, elegansols A-E (6-10), together with seven known diterpenoids (11-17). The structure elucidation of the new compounds was achieved by HRESIMS, NMR, and ECD spectroscopic analysis. Compounds (1-5) are the first examples of 12,13-seco-diterpenoid-type compounds representing a decalin fused dihydropyran skeleton. Plausible biosynthetic pathways for compounds 1-5 are proposed. Aromatase inhibitory activities of all compounds were evaluated, and abieta-8,11,13-trien-11-ol (16) was found to be the most potent aromatase inhibitor with an IC₅₀ value of 3.7 μM.

Chemical Composition of Lipophilic Bark Extracts from Pinus pinaster and Pinus pinea Cultivated in Portugal

The chemical composition of lipophilic bark extracts from Pinus pinaster and Pinus pinea cultivated in Portugal was evaluated using gas chromatography-mass spectrometry. Diterpenic resin acids were found to be the main components of these lipophilic extracts, ranging from 0.96 g kg−1 dw in P. pinea bark to 2.35 g kg−1 dw in P. pinaster bark. In particular, dehydroabietic acid (DHAA) is the major constituent of both P. pinea and P. pinaster lipophilic fractions, accounting for 0.45 g kg−1 dw and 0.95 g kg−1 dw, respectively. Interestingly, many oxidized compounds were identified in the studied lipophilic extracts, including DHAA-oxidized derivatives (7-oxo-DHAA, 7α/β-hydroxy-DHAA, and 15-hydroxy-DHAA, among others) and also terpin (an oxidized monoterpene). These compounds are not naturally occurring compounds, and their formation might occur by the exposure of the bark to light and oxygen from the air, and the action of micro-organisms. Some of these compounds have not been previously reported as lipophilic constituents of the bark of the referred pine species. Other constituents, such as aromatic compounds, fatty acids, fatty alcohols, and sterols, are also present in the studied extracts. These results can represent an opportunity to valorize P. pinaster and P. pinea by-products as a primary source of the bioactive resin acids that are integrated into the current uses of these species.

Phytochemical study of Illicium angustisepalum and its biological activities

Sixteen compounds, including two new natural products (1 and 2), were obtained from the twigs of Illicium angustisepalum. The structures were elucidated based on NMR, MS, IR data and optical rotation values. Compounds 4, 5, 6 and 8 displayed moderate antibacterial activities against clinical isolates; compounds 4, 5, 8, 9 and 15 protected neural cells against oxidative stress; and compounds 10 and 14 exhibited anti-acetylcholinesterase activity.

New Abietane and Kaurane Type Diterpenoids from the Stems of Tripterygium regelii

Eleven new abietane type (1‒11), and one new kaurane (12), diterpenes, together with eleven known compounds (13-23), were isolated and identified from the stems of Tripterygium regelii, which has been used as a traditional folk Chinese medicine for the treatment of rheumatoid arthritis in China. The structures of new compounds were characterized by means of the interpretation of high-resolution electrospray ionization mass spectrometry (HRESIMS), extensive nuclear magnetic resonance (NMR) spectroscopic data and comparisons of their experimental CD spectra with calculated electronic circular dichroism (ECD) spectra. Compound 1 is the first abietane type diterpene with an 18→1 lactone ring. Compound 19 was isolated from the plants of the Tripterygium genus for the first time, and compounds 14-17 were isolated from T. regelii for the first time. Triregelin I (9) showed significant cytotoxicity against A2780 and HepG2 with IC50 values of 5.88 and 11.74 µM, respectively. It was found that this compound was inactive against MCF-7 cells. The discovery of these twelve new diterpenes not only provided information on chemical substances of T. regelii, but also contributed to the chemical diversity of natural terpenoids.

Therapeutic Potential of Essential Oils Focusing on Diterpenes

Among all plant derivates, essential oils (EOs) have gained the attention of many scientists. Diterpenes, a family of components present in some EO, are becoming a milestone in the EOs world. The goal of this review is to describe a scenario of diterpenes taking into health-consumption deportment. Previous studies revealed that diterpenes have antioxidant, antimicrobial, antiviral, antiprotozoal, cytotoxic, anticancer, antigenotoxic, antimutagenic, chemopreventive, antiinflammatory, antinociceptive, immunostimulatory, organoprotective, antidiabetic, lipid-lowering, antiallergic, antiplatelet, antithrombotic, and antitoxin activities. In conclusion, diterpenes may be an immense featuring concern in pharmaceutical consumption from a drug discovery point of view. Copyright © 2016 John Wiley & Sons, Ltd.

Synthetic Studies on Tricyclic Diterpenoids: Direct Allylic Amination Reaction of Isopimaric Acid Derivatives

A selective synthesis of 7- or 14-nitrogen containing tricyclic diterpenoids was completed according to a strategy in which the key step was the catalyzed direct allylic amination of methyl 14α-hydroxy-15,16-dihydroisopimarate with a wide variety of nitrogenated nucleophiles. It was revealed that the selectivity of the reaction depends on the nature of nucleophile. The catalyzed reaction of the mentioned diterpenoid allylic alcohol with 3-nitroaniline, 3-(trifluoromethyl)aniline, and 4-(trifluoromethyl)aniline yield the subsequent 7α-, 7β- and 14αnitrogen-containing diterpenoids. The reaction with 2-nitroaniline, 4-nitro-2-chloroaniline, 4-methoxy-2-nitroaniline, phenylsulfamide, or tert-butyl carbamate proceeds with the formation of 7α-nitrogen-substituted diterpenoids as the main products.

Anti-herpetic and anti-dengue activity of abietane ferruginol analogues synthesized from (+)-dehydroabietylamine

The abietane-type diterpenoid (+)-ferruginol (1), a bioactive compound isolated from several plants, has attracted much attention as consequence of its pharmacological properties, which includes antibacterial, antifungal, antimicrobial, cardioprotective, anti-oxidative, anti-plasmodial, leishmanicidal, anti-ulcerogenic, anti-inflammatory and antitumor actions. In this study, we report on the antiviral evaluation of ferruginol (1) and several analogues synthesized from commercial (+)-dehydroabietylamine. Thus, the activity against Human Herpesvirus type 1, Human Herpesvirus type 2 and Dengue Virus type 2, was studied. Two ferruginol analogues showed high antiviral selectivity index and reduced viral plaque-size in post-infection stages against both Herpes and Dengue viruses. A promising lead, compound 8, was ten-fold more potent (EC50 = 1.4 μM) than the control ribavirin against Dengue Virus type 2. Our findings suggest that the 12-hydroxyabieta-8,11,13-triene skeleton, which is characteristic of the diterpenoid ferruginol (1), is an interesting molecular scaffold for development of novel antivirals. In addition, the cytotoxic and antifungal activities of the synthesized ferruginol analogues have also been investigated. (©)20155 Elsevier Science. All rights reserved.

Aromatic abietane diterpenoids: their biological activity and synthesis

In this study, the biological properties of abietane-type diterpenoids with an aromatic C ring are reviewed. The review contains about 160 references.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December 2013 is reviewed.

Semisynthesis of the antiviral abietane diterpenoid jiadifenoic acid C from callitrisic acid (4-epidehydroabietic acid) isolated from sandarac resin

The semisynthesis of the antiviral abietane diterpenoid (+)-jiadifenoic acid C starting from the available methyl ester of callitrisic acid (4-epidehydroabietic acid) isolated from sandarac resin is reported. A protocol for the isolation of methyl callitrisate (methyl 4-epidehydroabietate) in gram quantities from sandarac resin is also described. Allylic C-17 oxygenation was introduced by regioselective dehydrogenation of the isopropyl group of methyl callitrisate with DDQ followed by selenium-catalyzed allylic oxidation. Ester hydrolysis afforded (+)-jiadifenoic acid C in 22% overall yield from methyl callitrisate. This semisynthetic route provides a convenient source of this anti-Coxsackie virus B natural product for further biological studies.

The antiviral effect of jiadifenoic acids C against coxsackievirus B3

Coxsackievirus B type 3 (CVB3) is one of the major causative pathogens associated with viral meningitis and myocarditis, which are widespread in the human population and especially prevalent in neonates and children. These infections can result in dilated cardiomyopathy (DCM) and other severe clinical complications. There are no vaccines or drugs approved for the prevention or therapy of CVB3-induced diseases. During screening for anti-CVB3 candidates in our previous studies, we found that jiadifenoic acids C exhibited strong antiviral activities against CVB3 as well as other strains of Coxsackie B viruses (CVBs). The present studies were carried out to evaluate the antiviral activities of jiadifenoic acids C. Results showed that jiadifenoic acids C could reduce CVB3 RNA and proteins synthesis in a dose-dependent manner. Jiadifenoic acids C also had a similar antiviral effect on the pleconaril-resistant variant of CVB3. We further examined the impact of jiadifenoic acids C on the synthesis of viral structural and non-structural proteins, finding that jiadifenoic acids C could reduce VP1 and 3D protein production. A time-course study with Vero cells showed that jiadifenoic acids C displayed significant antiviral activities at 0-6 h after CVB3 inoculation, indicating that jiadifenoic acids C functioned at an early step of CVB3 replication. However, jiadifenoic acids C had no prophylactic effect against CVB3. Taken together, we show that jiadifenoic acids C exhibit strong antiviral activities against all strains of CVB, including the pleconaril-resistant variant. Our study could provide a significant lead for anti-CVB3 drug development.

Diterpenoids and sesquiterpenoids from the roots of Illicium majus

Five new diterpenoids (1-5), five new sesquiterpenoids (6-10), and three known compounds (11-13) were isolated from the roots of Illicium majus. Their structures were elucidated by extensive spectroscopic analysis. The absolute configuration of 1 was assigned by X-ray crystallography, whereas those of the 1,2-diol moieties in 3 and 4 were determined using Snatzke's method. The abietane acids 1, 2, 11, 12, and 13 displayed antiviral activity against the Coxsackie B3 virus, with IC50 values of 3.3-51.7 μM/mL.

Sesquiterpenes and alkaloids from the roots of Alangium chinense

Four new sesquiterpenes (1-4), four new alkaloids (5a, 6a, 6b, and 7), and nine known compounds (5b and 8-15) were isolated from an ethanolic extract of roots of Alangium chinense. The structure of 1 was confirmed by X-ray crystallography. The configurations of 5 and 6 were assigned by chiral HPLC analysis and CD spectra. Compounds 3, 4, 8-13, and 15 exhibited antiviral activity against Coxsackie virus B3 with IC50 values of 1.4-15.4 μM. Compounds 2-4, 7, and 9-13 showed antioxidant activities against Fe(2+)-cysteine-induced rat liver microsomal lipid peroxidation, with IC50 values of 3.8-45.7 μM. Compound 5b displayed neuritis inhibitory activity against microglial inflammation factor, with an IC50 value of 6.7 μM. None of the compounds exhibited detectable cytotoxic activity toward any of five tumor cell lines (A549, Be-17402, BGC-823, HCT-8, and A2780) in the MTT assay.