New 7,20:14,20-diepoxy ent-kauranoids from Isodon xerophilus

Isoxerophilusins A and B, Two Novel Polycyclic Asymmetric Diterpene Dimers from Isodon xerophilus: Structural Elucidation, Modification, and Inhibitory Activities against α-Glucosidase

Isoxerophilusins A (1) and B (2), two unprecedented diterpene heterodimers biogenetically from ent-atisanes and abietanes, were isolated from the rhizomes of Isodon xerophilus. Their structures were determined by extensive spectroscopic analysis and single-crystal X-ray diffraction. Selective esterification of 1 generated 11 new derivatives. All derivatives showed excellent α-glucosidase inhibitory activity in comparison to acarbose. Compounds 12 and 13 demonstrated significant inhibition against α-glucosidase with IC50 values of 4.92 and 3.83 μM, respectively.

Pharmacophore based virtual screening for natural product database revealed possible inhibitors for SARS-COV-2 main protease

The challenge continues globally triggered by the absence of an approved antiviral drug against COVID-19 virus infection necessitating global concerted efforts of scientists. Nature still provides a renewable source for drugs used to solve many health problems. The aim of this work is to provide new candidates from natural origin to overcome COVID-19 pandemic. A virtual screening of the natural compounds database (47,645 compounds) using structure-based pharmacophore model and molecular docking simulations reported eight hits from natural origin against SARS-CoV-2 main proteinase (Mpro) enzyme. The successful candidates were of terpenoidal nature including taxusabietane, Isoadenolin A & C, Xerophilusin B, Excisanin H, Macrocalin B and ponicidin, phytoconstituents isolated from family Lamiaceae and sharing a common ent-kaurane nucleus, were found to be the most successful candidates. This study suggested that the diterpene nucleus has a clear positive contribution which can represent a new opportunity in the development of SARS-CoV-2 main protease inhibitors.

Quantitative Analysis of Ent-Kaurane Diterpenoids in Isodon Herb (Enmei-So) by HPLC-UV

The terrestrial plants, Isodon japonicus (Burm. f.) H. Hara and Isodon trichocarpus (Maxim.) Kudô (Labiatae), are native to Japan. Different parts of these plants have been used as a traditional bitter stomachic, under the name Isodon herb (Enmei-so). Ent-kaurane diterpenoids are the major constituents of Isodon herb that contribute to the herb's medicinal properties. However, large variability with respect to the composition of these diterpenoids limits the suitability of Isodon herb as a pharmaceutical ingredient. Thus, an investigation of the factors that affect its chemical composition is required. In this study, the DNA-barcoding method, using internal transcribed spacer sequences of nuclear ribosomal DNA, was applied to cultivated and commercial samples of Isodon herb. Further, each such sample was separated into leaves, stems, and flowers and analyzed for diterpenoid content by HPLC. Moreover, the diterpenoid content in coarsely cut and powdered samples was evaluated. Results confirmed that the source species of these samples was I. japonicus or I. trichocarpus. The three major diterpenoids in Isodon herb were enmein, oridonin, and ponicidin. The diterpenoid content was affected by milling process. Moreover, the diterpenoid content was greatly affected by the ratio between leaves and stems in each sample. Thus, to accurately quantify the diterpenoids in Isodon herb, the use specific conditions such as drying using mild temperature conditions and avoiding milling of the samples might be necessary. This may help in regulating variations in the herb's composition, in turn, providing better quality and a safe herbal product for pharmaceutical use.

ent-Kaurane-Based Diterpenoids, Dimers, and Meroditerpenoids from Isodon xerophilus

Eight new diterpenoids (1-8) with varied structures were isolated from the aerial parts of Isodon xerophilus. Among them, xerophilsin A (1) was found to be an unusual meroditerpenoid representing a hybrid of an ent-kauranoid and a long-chain aliphatic ester, xerophilsins B-D (2-4) are dimeric ent-kauranoids, while xerophilsins E-H (5-8) are new ent-kauranoids. The structures of 1-8 were elucidated mainly through the analyses of their spectroscopic data. The absolute configurations of 2, 6, and 8 were confirmed by single-crystal X-ray diffraction, and the configuration of C-16 in 7 was established through quantum chemical calculation of NMR chemical shifts, as well as modeling of key interproton distances. Bioactivity evaluation of all isolated compounds revealed that 2, 3, and 5 inhibited NO production in LPS-stimulated RAW264.7 cells.

1-O-Acetylgeopyxin A, a derivative of a fungal metabolite, blocks tetrodotoxin-sensitive voltage-gated sodium, calcium channels and neuronal excitability which correlates with inhibition of neuropathic pain

Chronic pain can be the result of an underlying disease or condition, medical treatment, inflammation, or injury. The number of persons experiencing this type of pain is substantial, affecting upwards of 50 million adults in the United States. Pharmacotherapy of most of the severe chronic pain patients includes drugs such as gabapentinoids, re-uptake blockers and opioids. Unfortunately, gabapentinoids are not effective in up to two-thirds of this population and although opioids can be initially effective, their long-term use is associated with multiple side effects. Therefore, there is a great need to develop novel non-opioid alternative therapies to relieve chronic pain. For this purpose, we screened a small library of natural products and their derivatives in the search for pharmacological inhibitors of voltage-gated calcium and sodium channels, which are outstanding molecular targets due to their important roles in nociceptive pathways. We discovered that the acetylated derivative of the ent-kaurane diterpenoid, geopyxin A, 1-O-acetylgeopyxin A, blocks voltage-gated calcium and tetrodotoxin-sensitive voltage-gated sodium channels but not tetrodotoxin-resistant sodium channels in dorsal root ganglion (DRG) neurons. Consistent with inhibition of voltage-gated sodium and calcium channels, 1-O-acetylgeopyxin A reduced reduce action potential firing frequency and increased firing threshold (rheobase) in DRG neurons. Finally, we identified the potential of 1-O-acetylgeopyxin A to reverse mechanical allodynia in a preclinical rat model of HIV-induced sensory neuropathy. Dual targeting of both sodium and calcium channels may permit block of nociceptor excitability and of release of pro-nociceptive transmitters. Future studies will harness the core structure of geopyxins for the generation of antinociceptive drugs.

Acetyl-macrocalin B, an ent-kaurane diterpenoid, initiates apoptosis through the ROS-p38-caspase 9-dependent pathway and induces G2/M phase arrest via the Chk1/2-Cdc25C-Cdc2/cyclin B axis in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide, and novel effective drugs against NSCLC are urgently needed. Isodon species are rich in ent-kaurane diterpenoids that have been reported to have antitumor bioactivity. Acetyl-macrocalin B (A-macB) is a novel ent-kaurane diterpenoid isolated from Isodon silvatica, and its antitumor efficacy against NSCLC and the underlying mechanisms were scrutinized in depth. The viability of cells treated with A-macB was detected by CCK-8 and colony formation assays. Apoptosis and cell cycle distribution were analyzed by flow cytometry. The mechanisms were investigated by detecting ROS and performing western blotting and verification experiments with specific inhibitors. The in vivo effect of A-macB was explored in a nude mouse xenograft model. A-macB effectively inhibited H1299 and A549 cell viability, triggered apoptosis and delayed cells in the G2/M phase. A-macB induced cellular ROS production and then activated the p38 MAPK-mediated, caspase 9-dependent apoptotic pathway. Both the ROS scavenger NAC and the specific p38 inhibitor SB203580 inactivated the function of p38 induced by A-macB, thus preventing cells from apoptosis. A-macB activated the Chk1/2-Cdc25C-Cdc2/cyclin B1 axis to induce G2/M phase arrest. AZD7762 abrogated the function of Chk1/2, abolished the G2/M delay and enhanced the cytotoxicity of A-macB. Moreover, A-macB efficiently suppressed tumor growth in a mouse xenograft model without noticeable toxicity to normal tissues. Having both efficacy and relative safety, A-macB is a potential lead compound that is worthy of further exploration for development as an anticancer agent.

Two cytotoxic 6,7-seco-spiro-lacton-ent-kauranoids from Isodon rubescens

The present study was performed to investigate the chemical components of the branches and leaves of Isodon rubescens. Two 6,7-seco-spiro-lacton-ent-kauranoids were obtained. Based on the extensive spectroscopic analyses, their structures were elucidated as 6-epi-11-O-acetylangustifolin (1) and 11-O-acetylangustifolin (2), respectively. The structure of 2 was further comfirmed by X-ray crystallography analysis. MTT method was employed to evaluate their cytotoxity against human lung cancer cell lines A549 and leukemia cell lines K562.

Xerophilusin B induces cell cycle arrest and apoptosis in esophageal squamous cell carcinoma cells and does not cause toxicity in nude mice

Esophageal cancer is the eighth most common cancer in the world and ranks as the sixth leading cause of cancer-related mortality. Esophageal cancer has a poor prognosis partially due to its low sensitivity to chemotherapy agents, and the development of new therapeutic agents is urgently needed. Here, the antitumor activity of a natural ent-kaurane diterpenoid, xerophilusin B (1), which was isolated from Isodon xerophilus, a perennial herb frequently used in Chinese folk medicine for tumor treatment, was investigated. Compound 1 exhibited antiproliferative effects against esophageal squamous cell carcinoma (ESCC) cell lines in a time- and dose-dependent manner with lower toxicity against normal human and murine cell lines. In vivo studies demonstrated that 1 inhibited tumor growth of a human esophageal tumor xenograft in BALB/c nude mice without significant secondary adverse effects, indicating its safety in treating ESCC. Furthermore, 1 induced G2/M cell cycle arrest and promoted apoptosis through mitochondrial cytochrome c-dependent activation of the caspase-9 and caspase-3 cascade pathway in ESCC cell lines. In conclusion, the observations herein reported showed that 1 is a potential chemotherapeutic agent for ESCC and merits further preclinical and clinical investigation for cancer drug development.

Geopyxins A-E, ent-kaurane diterpenoids from endolichenic fungal strains Geopyxis aff. majalis and Geopyxis sp. AZ0066: structure-activity relationships of geopyxins and their analogues

Four new ent-kaurane diterpenoids, geopyxins A-D (1-4), were isolated from Geopyxis aff. majalis, a fungus occurring in the lichen Pseudevernia intensa, whereas Geopyxis sp. AZ0066 inhabiting the same host afforded two new ent-kaurane diterpenoids, geopyxins E and F (5 and 6), together with 1 and 3. The structures of 1-6 were established on the basis of their spectroscopic data, while the absolute configurations were assigned using modified Mosher's ester method. Methylation of 1-3, 5, and 6 gave their corresponding methyl esters 7-11. On acetylation, 1 and 7 yielded their corresponding monoacetates 12 and 14 and diacetates 13 and 15. All compounds were evaluated for their cytotoxic and heat-shock induction activities. Compounds 2, 7-10, 12, 14, and 15 showed cytotoxic activity in the low micromolar range against all five cancer cell lines tested, but only compounds 7-9, 14, and 15 were found to activate the heat-shock response at similar concentrations. From a preliminary structure-activity perspective, the electrophilic α,β-unsaturated ketone carbonyl motif present in all compounds except 6 and 11 was found to be necessary but not sufficient for both cytotoxicity and heat-shock activation.

Isorosthornins A-C, new ent-kaurane diterpenoids from Isodon rosthornii

Three new ent-kauranoids, isorosthornins A-C (1–3), and a new natural product, dihydroponicidin (4), together with five known ones were isolated from the aerial parts of Isodon rosthornii. The structures were determined by means of extensive spectroscopic analysis. All diterpenoids isolated were evaluated for their cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cell lines, and compounds 5 and 7 showed significant inhibitory effects on all cell lines.

Structure and cytotoxicity of diterpenoids from Isodon adenolomus

Twelve new diterpenoids, isoadenolins A-L (1-12), and 24 known ones were isolated from the aerial parts of Isodon adenolomus. Their structures were identified using spectroscopic data, and the absolute configurations of 1 and 14 were determined by single-crystal X-ray diffraction. Selected compounds were evaluated for their in vitro cytotoxicity against human tumor HL-60, SMMC-7721, A-549, MCF-7, and SW-480 cell lines. Compounds 9, 13-16, and 21 showed significant inhibitory effects on all five cells, with IC50 values in the range 0.7-9.7 μM.

Inhibition of NF-kappaB activation and iNOS induction by ent-kaurane diterpenoids in LPS-stimulated RAW264.7 murine macrophages

Xerophilusin A (1), xerophilusin B (2), longikaurin B (3), and xerophilusin F (4) from Isodon xerophylus inhibit LPS-induced NO production in RAW 264.7 macrophages, with IC(50) values of 0.60, 0.23, 0.44, and 0.67 muM, respectively, and they all inhibited mRNA production in these same cells. They decreased the luciferase activity in RAW 264.7 cells transiently transfected with the NF-kappaB-dependent luciferase reporter, with IC(50) values of 1.8, 0.7, 1.2, and 1.6 muM, respectively. Compounds 1-3 reduced NF-kappaB activation, with compound 4 showing no effect, but p65 translocation from the cytoplasm to the nucleus and the LPS-induced degradation of IkappaB were inhibited by all four test compounds. These findings indicate that ent-kauranes are potential anti-inflammatory agents, with a specific mechanism in which both the inhibition of NF-kappaB translocation and the consequent decrease of pro-inflammatory mediators are implicated.

Negative electrospray ionization tandem mass spectrometric investigation of ent-kaurane diterpenoids from the genus Isodon

ent-Kaurane diterpenoids are a class of natural compounds isolated from genus Isodon, which have been found to have important bioactivities. Negative electrospray ionization tandem mass spectrometry ((-)ESI-MS(n)) was used to investigate the fragmentation pattern of C-20-nonoxygenated ent-kauranes and two subtypes of C-20-oxygenated ent-kauranes by using an ion trap instrument and accurate mass measurement on an ESI-Q-time-of-flight (TOF) mass spectrometer. The analysis revealed that loss of CH(2)O or CO(2) is the predominant process for 7, 20-epoxy and 7, 20 : 14, 20-diepoxy subgroup of C-20-oxygenated ent-kauranes. In addition, compounds of C-20-nonoxygenated ent-kauranes with a conserved core structure but different substituent groups, such as a hydroxyl, aldehyde, carboxyl, and acetyl moiety, resulted in diagnostic product ions through losses of H(2)O, CO, CO(2), and AcOH, respectively. This work clearly demonstrates the utility of tandem mass spectrometry for studies on the rationalization of the diagnostic fragmentation of a series of compounds from two main types of the ent-kaurane diterpenoids.

Isoprenylated xanthones and flavonoids from Cudrania tricuspidata

Further phytochemical investigation on the roots of Cudrania tricuspidata afforded a new isoprenylated xanthone, cudratricusxanthone I (1), two new isoprenylated flavanones, cudraflavanones C and D (2 and 3, resp.), and seven known compounds, 1,7-dihydroxy-3,6-dimethoxyxanthone (4), macluraxanthone C (5), cudraxanthones E, K, and L (6, 7, and 8, resp.), cudraflavanone A (9), and cudraflavone C (10). Their structures were identified by spectroscopic methods. Cudratricusxanthone H (12), macluraxanthone B (13), two xanthones previously isolated from this plant, and 5, showed significant inhibitory effects on four kinds of human digestive apparatus tumor cell lines (HCT-116, SMMC-7721, SGC-7901, and BGC-823) with IC50 values of 2.70-12.66 microM.

Two new chemical constituents fromDaphne odoraThunb. var.marginata

Two new phenolic constituents, daphnenone (1) and daphneone (2), were isolated from the stem bark of Daphne odora Thunb. var. marginata. Their structures were established on the basis of spectroscopic analysis. Compounds 1 and 2 were tested for cytotoxic activity by MTT assays on five human tumour cell lines, K562, A549, MCF-7, LOVO and HepG2. Compound 1 showed obvious cytotoxic activity against all the five cell lines.

Diterpenoids from Isodon species and their biological activities

Isodon species (Labiatae) are widely distributed plants, many of which are used in folk medicine. Over the past twenty years, they have received considerable phytochemical and biological attention. Thestructures of their many diterpenoids constituents, especially those with an ent-kaurane skeleton, have been elucidated. The significant phytochemical and pharmacological diterpenoids form the subject of this review. There are 290 references.

New flavonol glycosides and new xanthone from Polygala japonica

Three new flavonol glycosides and a new xanthone were isolated from Polygala japonica HOUTT. with eight known compounds. Their structures were identified as 1,7-dihydroxy-3,4-dimethoxy-xanthone (1), kaempferol-7,4'-dimethyl ether (2), physcion (3), guazijinxanthone (4), rhamnetin (5), polygalin A (6), 3,5,7-trihydroxy-4'-methoxy-flavone-3-O-beta-d-galactopyranoside (7), 3,5,3'-trihydoxy-7,4'-dimethoxy-flavone-3-O-beta-d-galactopyranoside (8), 3,5,3',4'-tetrahydroxy-7-methoxy-flavone-3-O-beta-d-galactopyranoside (9), 3,5,3',4'-tetrahydroxy-7-methoxy-flavone-3-O-beta-d-glucopyranoside (10), polygalin B (11), polygalin C (12). Among them, compound 4 is a new xanthone, and 6, 11 and 12 are new flavonol glycosides. Compounds 1, 4, 7 and 8 were tested for cytotoxic activity with MTT assays on five human tumor cell lines, K562, A549, PC-3M, HCT-8 and SHG-44. Compound 4 showed cytotoxic activity against all the five cell lines.

Cytotoxicent-Kaurane Diterpenoids fromIsodon eriocalyx

Five new ent-kaurane diterpenoids, epi-maoecrystal N (1), eriocalyxin G (2), maoecrystal W (3), maoecrystal X (4), and maoecrystal Y (5), along with 22 known ones, were isolated from Isodon eriocalyx (Dunn.) Hara., and their structures were determined by spectroscopic methods. All diterpenoids, except for 3 and 13, were evaluated for inhibition of the K562, T-24, Me180, QGY-7701, and BIU87 cell lines (Table 2).

Cytotoxic ent-kauranoids from Isodon leucophyllus

Two new compounds, baiyecrystals D and E (1, 2), together with eight known analogues, xerophilusin B (4), macrocalin B (5), oridonin (6), rosthorin A (7), lasiocarpanin (8), rabdoternin A (9) and phyllostachysin A (10) and B (11), were isolated from the aerial parts of Isodon leucophyllus. The structures of 1 and 2 and 4-11 were elucidated on the basis of spectroscopic methods, especially the 2D NMR spectral analysis. Compounds 2, 6-8 and 10 were evaluated for their antineoplastic activities in vitro. Among them, lasiocarpanin (8) showed significant inhibitory activities against K562 and Bcap37 cells, with the IC50 values of 0.13 and 1.26 microg mL(-1), respectively, which were lower than those of the positive control.

Cytotoxic isoprenylated xanthones from Cudrania tricuspidata

Eight new isoprenylated xanthones, cudratricusxanthones A-H (1-8), were isolated from the roots of Cudrania tricuspidata, together with ten known compounds, cudraxanthones H (9) and M (10), xanthone V(1a) (11), toxyloxanthone C (12), macluraxanthone B (13), 1-hydroxy-3, 6, 7-trimethoxyxanthone (14), cycloartocarpesin (15), artocarpesin (16), cudraflavone B (17), and kaempferol (18). Their structures were characterized by spectroscopic methods. Xanthones 5, 7, 10, and 12 showed inhibitory effects on four kinds of human digestive apparatus tumor cell lines (HCT-116, SMMC-7721, SGC-7901, and BGC-823) with IC(50) values of 1.6-11.8 microg/mL. Xanthones 2, 4, and 11 displayed significant cytotoxicity against HCT-116, SMMC-7721, and SGC-7901 (IC(50)=1.3-9.8 microg/mL). Flavonoids 15-17 were almost inactive.

The cytotoxic and embryotoxic effects of kaurenoic acid, a diterpene isolated from Copaifera langsdorffii oleo-resin

In this work, we studied the effects of kaurenoic acid, a diterpene isolated from the oleo-resin of Copaifera langsdorffii in developing sea urchin (Lytechinus variegatus) embryos, on tumor cell growth in microculture tetrazolium (MTT) test and on mouse and human erythrocytes in hemolysis assay. Continuous exposure of embryos to kaurenoic acid starting immediately after fertilization inhibited the first cleavage (IC(50): 84.2 microM) and progressively induced embryo destruction (IC(50): 44.7 microM and < 10 microM for blastulae and larvae stages, respectively). In MTT assay, kaurenoic acid at a concentration of 78 microM produced growth inhibition of CEM leukemic cells by 95%, MCF-7 breast and HCT-8 colon cancer cells by 45% each. Further, kaurenoic acid induced a dose-dependent hemolysis of mouse and human erythrocytes with an EC(50) of 74.0 and 56.4 microM, respectively. The destruction of sea urchin embryos, the inhibition of tumor cell growth and the hemolysis of mouse and human erythrocytes indicate the potential cytotoxicity of kaurenoic acid.

Diterpenoids from Isodon enanderianus

Four ent-kauranoids, 6-epiangustifolin and enanderinanins F-H, as well as 11 known ent-kaurane diterpenoids, macrocalin B, xerophilusin A, trichorabdal A, trichorabdal B, effusin, angustifolin, longikaurin D, longikaurin F, enanderinanin B, xerophilusin G and shikokianin were isolated from the aerial parts of Isodon enanderianus. The new diterpenoids were identified as 6-epiangustifolin (11alpha-hydroxy-6alpha-methoxy-6,19-epoxy-6,7-seco-ent-kaur-16-en-15-one-7,20-olide), enanderinanin F (19-acetoxy-6,20:6,11beta-diepoxy-6,7-seco-ent-kaur-16-en-15-one-1beta,7-olide), enanderinanin G (1beta,6beta,7beta-trihydroxy-19-acetoxy-16beta-methoxymethyl-7alpha,20-epoxy-ent-kaur-15-one) and enanderinanin H (6beta,7beta,14beta-trihydroxy-1alpha,11beta-acetonide-7alpha,20-epoxy-ent-kaur-16-en-15-one), respectively, on the basis of spectral data, especially by 2D NMR techniques. 6-Epiangustifolin showed significant cytotoxic activity against K562 cell.

Cytotoxic 7,20-epoxy ent-kauranoids from Isodon xerophilus

Four 7,20-epoxy ent-kaurane diterpenoids, xerophilusins G (1) and I-K (2-4), were isolated from the leaves of Isodon xerophilus, along with four known ones, enanderianin C (5), rosthorin A (6), longikaurin B (7), and rabdoternin D (8). Their structures were determined primarily using NMR spectroscopic techniques. The structure and stereochemistry of 3 were confirmed by X-ray crystallography. Compounds 4 and 7 exhibited broad cytotoxicity against four kinds of human tumor cells (K562, HL-60, HCT, and MKN-28 cells) in the range of 2.23-15.35 and 0.30-8.61 microg/ml, respectively.

Inhibition of the nuclear factor kappa B (NF-kappa B) pathway by tetracyclic kaurene diterpenes in macrophages. Specific effects on NF-kappa B-inducing kinase activity and on the coordinate activation of ERK and p38 MAPK

The anti-inflammatory action of most terpenes has been explained in terms of the inhibition of nuclear factor kappaB (NF-kappaB) activity. Ent-kaurene diterpenes are intermediates of the synthesis of gibberellins and inhibit the expression of NO synthase-2 and the release of tumor necrosis factor-alpha in J774 macrophages challenged with lipopolysaccharide. These diterpenes inhibit NF-kappaB and IkappaB kinase (IKK) activation in vivo but failed to affect in vitro the function of NF-kappaB, the phosphorylation and targeting of IkappaBalpha, and the activity of IKK-2. Transient expression of NF-kappaB-inducing kinase (NIK) activated the IKK complex and NF-kappaB, a process that was inhibited by kaurenes, indicating that the inhibition of NIK was one of the targets of these diterpenes. These results show that kaurenes impair the inflammatory signaling by inhibiting NIK, a member of the MAPK kinase superfamily that interacts with tumor necrosis factor receptor-associated factors, and mediate the activation of NF-kappaB by these receptors. Moreover, kaurenes delayed the phosphorylation of p38, ERK1, and ERK2 MAPKs, but not that of JNK, in response to lipopolysaccharide treatment of J774 cells. The absence of a coordinate activation of MAPK and IKK might contribute to a deficient activation of NF-kappaB that is involved in the anti-inflammatory activity of these molecules.