Diterpenoids from Croton laui and their cytotoxic and antimicrobial activities

Lauinoids A-X: Labdane-type diterpenoids with anti-inflammatory activity from Croton laui

Croton laui (Euphorbiaceae) is a traditional medicinal plant used by the Li ethnic group in China to treat headaches, stomachaches, and diphtheria. To understand the pharmacological basis of its medicinal use, an extensive investigation of the ethanolic extract of the bark of C. laui was performed. After repeated chromatography, twenty-four undescribed labdane-type diterpenoids, lauinoids A-X (1-24), and five known analogs (25-29) were isolated. Their structures and absolute configurations were established using a combination of spectroscopic analyses, electronic circular dichroism, nuclear magnetic resonance calculations, and single-crystal X-ray diffraction. Among them, compounds 1-3 exhibited an 11(12 → 13)-abeo-16-nor-labdane skeleton, which originated putatively from 9 through a plausible pathway that involves a semipinacol rearrangement process. Compounds 11 and 12 belong to the rare class of 14,15-dinor-labdane diterpenoids. Compounds 18 and 28 exhibited substantial inhibitory effects by suppressing lipopolysaccharide-induced NO production in RAW 264.7 macrophages, with IC50 values of 3.37 ± 0.23 and 5.82 ± 0.28 μM, respectively. This study has greatly expanded the chemical diversity of labdane diterpenoids from C. laui and will guide future research on this ethnomedicinal plant.

Discovery of potential components characteristic by conjugated enone from the branches and leaves of Croton lauioides with anti-neuroinflammatory activity via regulating the NF-κB pathway

In this study, the chemical composition and pharmacological activity of Croton lauioides were investigated for the first time. The bioactive and HPLC-UV guided isolation led to the discovery of twenty-three conjugated enone-type components (1-23), including nine previously unknown sesquiterpenoid derivatives (1-4, 9-10, 12-14). Notably, compounds 1 and 12 are epoxides containing an endoperoxide bridge (1) or a unique dioxaspiro core (12), respectively. Compounds 2-7 are non-benzenoid aromatics featuring a tropone function, while 9-11 possess a rare rearranged scaffold with tropone shift into benzene. Extensive characterization was performed using NMR spectra, HRESIMS data, and electronic circular dichroism (ECD) calculations. Furthermore, we evaluated the bioactivities of all isolated compounds against neuroinflammation in LPS-stimulated BV-2 microglial cells. Remarkably, most sesquiterpenoid derivatives exhibited significant NO inhibit activities, and compound 5 showed the most potent effect with an IC50 value of 0.14 ± 0.04 μM. Structure-activity relationship (SAR) analysis revealed that sesquiterpenoids modified with endocyclic enone conjugation may serve as a key pharmacophore for NO inhibition, particularly involving aromatic tropone moiety. The qPCR and Western blot results demonstrated that 5 exerted an inhibitory effect on the mRNA levels of iNOS, TNF-α and COX-2 in a time-dependent manner, as well as suppressed the protein expression of iNOS, TNF-α, COX-2. In mechanism, 5 could prevented activation of NF-κB pathway by suppressing phosphorylation of p65 and IκB-α. These findings revealed C. lauioides might be a promising resource for drug candidate development targeting neuroinflammation.

A new diterpenoid from the leaves and twigs of Croton lachnocarpus Benth

A new clerodane diterpenoid, crotolanin A (1), along with three known clerodane diterpenoids, crotoeurin B (2), teucvidin (3) and teucvin (4), was isolated from the ethanol extract of the leaves and twigs of Croton lachnocarpus Benth. Their structures were identified by extensive NMR spectroscopic and HRESIMS analyses. The dopaminergic neuroprotective activity of compounds 1-4 was tested by using transgenic Caenorhabditis elegans pathological model. Compound 2 alleviated dopaminergic neuron degeneration of worms induced by 6-hydroxydopamine (6-OHDA) that represented a potential therapy for Parkinson's disease (PD).

Lycocasine A, a Lycopodium Alkaloid from Lycopodiastrum casuarinoides and Its Acid-Sensing Ion Channel 1a Inhibitory Activity

A novel Lycopodium alkaloid, lycocasine A (1), and seven known Lycopodium alkaloids (2-8), were isolated from Lycopodiastrum casuarinoides. Their structures were determined through NMR, HRESIMS, and X-ray diffraction analysis. Compound 1 features an unprecedented 5/6/6 tricyclic skeleton, highlighted by a 5-aza-tricyclic[6,3,1,02,6]dodecane motif. In bioactivity assays, compound 1 demonstrated weak inhibitory activity against acid-sensing ion channel 1a.

Bioactive cholinesterase inhibitions of clerodanes from the flowers of Croton krabas and molecular docking studies

The first investigation of the phytochemical profile of the flowers of Croton krabas led to the isolation of two new clerodane diterpenes, 6S-crotocaudin (1) and crotocaudin B (2), together with two known clerodanes, 6S-crotoeurin C (3) and isoteucvin (4). The structures and absolute configurations of isolated clerodanes were elucidated by extensive analysis of NMR spectroscopic data, mass spectrometry and ECD calculations. Compounds 1-4 demonstrated significant inhibitory activity towards acetylcholinesterase (AChE). Notably, compound 2 exhibited the strongest AChE inhibition (IC50 1.01 µM). Compounds 3 and 4 showed potent butyrylcholinesterase (BChE) inhibitory activity with IC50 values of 1.09 and 1.12 µM, respectively. The molecular docking results revealed that 2 bound to the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE, while 3 occupied in the CAS of BChE.

Nature's Green Potential: Anticancer Properties of Plants of the Euphorbiaceae Family

The number of cancer cases will reach 24 million in 2040, according to the International Agency for Research on Cancer. Current treatments for cancer are not effective and selective for most patients; for this reason, new anticancer drugs need to be developed and researched enough. There are potentially useful drugs for cancer isolated from plants that are being used in the clinic. Available information about phytochemistry, traditional uses, in vitro and in vivo experiments with plants, and pure compounds isolated from the Euphorbiaceae family indicates that this family of plants has the potential to develop anticancer drugs. This review examines selected species from the Euphorbiaceae family and their bioactive compounds that could have potential against different types of cancer cells. It reviews the activity of crude extracts, isolated compounds, and nanoparticles and the potential underlying mechanisms of action.

A New Clerodane from the Leaves of Croton krabas and Its Cholinesterase Inhibitory Activities

Chromatographic separation of the leaves of Croton krabas resulted in the isolation of one new clerodane, crotoeurin D (1), along with two known compounds, 6S-crotoeurin C (2) and blumenol A (3). Their structures were determined based on extensive nuclear magnetic resonance spectroscopic data analysis and mass spectrometry. The absolute configuration of the new clerodane was assigned by nuclear overhauser effect spectroscopy correlations and electronic circular dichroism calculations. Compound 1 exhibited significant acetylcholinesterase and butyrylcholinesterase inhibitory activities. Moreover, the binding modes of 1 revealed that its structure formed strong hydrogen bonds and hydrophobic interactions with the active sites of both enzymes.

Synthesis and screening of clerodane diterpene analogues from 16 hydroxycleroda 3,13(14)-Z-diene 15,16-olide for potential anti-mycobacterial activity

In recent years, clerodane diterpenes, a class of bioactive compounds, have come into the spotlight due to their amazing bioactivities. Three novel clerodane diterpene analogues were obtained by synthesising 16-hydroxycleroda-3,13(14)-Z-diene-15,16-olide (Lactone) with primary amines. Anti-tubercular activity was determined using Microplate Alamar Blue Assay. Among all the synthesised compounds from methanolic extract of seeds, results clearly showed that compounds 3 and 5 have significant anti TB activity with an MIC of 1.56 µg/ml against the Mycobacterium tuberculosis MTB H37Rv bacilli strain than the gold standard drugs pyrazinamide (3.13 µg/ml), ciprofloxacin (3.13 µg/ml), streptomycin (6.25 µg/ml) and rifampicin (6.25 µg/ml). Compound 5 exhibited significant antibacterial activity with zone of inhibition of 10.8 mm with Gram + ve and 7.95 mm with Gram -ve bacteria at a conc of 50 µg/ml respectively. In the current investigation, three novel heterocycles (compounds 3-5) of the diterpenoid were prepared, in high yield, using one-pot, efficient approach.

New halimane and clerodane diterpenoids from Croton cnidophyllus

Three new halimane furanoditerpenoids (1-3) and three new clerodane furanoditerpenoids (4-6), along with seven known terpenoids including four pimarane diterpenoids (7-10) and three norisoprenoids (11-13) were isolated from the 95% EtOH extracts of the plants of Croton cnidophyllus. The 2D structures including absolute configuration of new furanoditerpenoids (1-6) were elucidated by analysis of their HRMS and NMR data as well as comparison of experimental and calculated ECD curves. Bioassay revealed that two compounds (8 and 9) possessed certain inhibitory effects against NO production stimulated by LPS, with IC₅₀ values of 19.00 ± 1.76 and 21.61 ± 1.11 μM, respectively.

Antibacterial and Antifungal Terpenes from the Medicinal Angiosperms of Asia and the Pacific: Haystacks and Gold Needles

This review identifies terpenes isolated from the medicinal Angiosperms of Asia and the Pacific with antibacterial and/or antifungal activities and analyses their distribution, molecular mass, solubility, and modes of action. All data in this review were compiled from Google Scholar, PubMed, Science Direct, Web of Science, ChemSpider, PubChem, and library searches from 1968 to 2022. About 300 antibacterial and/or antifungal terpenes were identified during this period. Terpenes with a MIC ≤ 2 µg/mL are mostly amphiphilic and active against Gram-positive bacteria, with a molecular mass ranging from about 150 to 550 g/mol, and a polar surface area around 20 Ų. Carvacrol, celastrol, cuminol, dysoxyhainic acid I, ent-1β,14β-diacetoxy-7α-hydroxykaur-16-en-15-one, ergosterol-5,8-endoperoxide, geranylgeraniol, gossypol, 16α-hydroxy-cleroda-3,13 (14)Z-diene-15,16-olide, 7-hydroxycadalene, 17-hydroxyjolkinolide B, (20R)-3β-hydroxy-24,25,26,27-tetranor-5α cycloartan-23,21-olide, mansonone F, (+)-6,6'-methoxygossypol, polygodial, pristimerin, terpinen-4-ol, and α-terpineol are chemical frameworks that could be candidates for the further development of lead antibacterial or antifungal drugs.

Highly Oxygenated Labdane Diterpenoids from Stevia rebaudiana and Their Anti-Atherosclerosis Activities

Five unknown labdane diterpenoids Stevelins A-E (1-5), three known labdane diterpenoids (6-8) and three labdane norditerpenoids (9-11) were isolated from the Stevia rebaudiana. The structures were determined primarily via NMR spectroscopic data and HR-ESI-MS experiments. X-ray crystallography using CuK_α radiation was used to determine the absolute configurations of 1, and the absolute configurations of 2-5 were deduced by electronic circular dichroism (ECD) calculations. The potential anti-atherosclerosis activities of all compounds were evaluated by measuring their inhibitory effects on the macrophage foam cell formation. As a result, most isolated compounds could significantly inhibit oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cell formation, which suggests that these compounds may be promising candidates in the treatment for atherosclerosis.

Antimicrobial diterpenoids from the leaves and twigs of Croton kongensis Gagnepain

Croton kongensis Gagnepain. belongs to the genus Croton, the Euphorbiaceae family, mainly distributed in Hainan and southern Yunnan, China. The aim of present study was to acquire secondary metabolites of the ethanol extract obtained from the leaves and twigs of C. kongensis. Three new abietane-type diterpenoids, crokongenolides A-C (1-3), together with seven known diterpenoids (4-10), were isolated from the leaves and twigs of C. kongensis. The structures of the new compounds were determined by extensive spectroscopic methods (1D and 2D NMR, IR, and HRESIMS), and their absolute configurations were confirmed by single-crystal X-ray diffraction analysis or electronic circular dichroism (ECD) calculations. The absolute configuration of 4 was determined for the first time by single-crystal X-ray diffraction analysis with Cu-Kα irradiation. Some compounds were evaluated for their antimicrobial properties by assessing their inhibitory effects on Staphylococcus aureus, Candida albicans, and Escherichia coli. Compound 10 showed significant antimicrobial activity against S. aureus with MIC value of 1.56 μg/ml.

Molecular Docking, Validation, Dynamics Simulations, and Pharmacokinetic Prediction of Phytochemicals Isolated From Croton dichogamus Against the HIV-1 Reverse Transcriptase

The human immunodeficiency virus (HIV) infection and the associated acquired immune deficiency syndrome (AIDS) remain global challenges even after decades of successful treatment, with eastern and southern Africa still bearing the highest burden of disease. Following a thorough computational study, we report top 10 phytochemicals isolated from Croton dichogamus as potent reverse transcriptase inhibitors. The pentacyclic triterpenoid, aleuritolic acid (L12) has displayed best docking pose with binding energy of -8.48 kcal/mol and Ki of 0.61 μM making it superior in binding efficiency when compared to all docked compounds including the FDA-approved drugs. Other phytochemicals such as crotoxide A, crothalimene A, crotodichogamoin B and crotonolide E have also displayed strong binding energies. These compounds could further be investigated as potential antiretroviral medication.

Antimicrobial abietane-type diterpenoids from Torreya grandis

Twelve undescribed abietane-type diterpenoids, along with ten known analogues were isolated from the twigs and leaves of Torreya grandis var. merrillii Hu. Their structures were characterized by spectroscopic data analyses, single-crystal X-ray diffraction, and ECD spectra. Torgranols A-C possess three different architectures shaped via a common 6,7-seco-procedure and subsequent ring formations. In particular, torgranol A represents the first example of a 6,7-seco-abietane diterpenoid featuring a unique oxygen bridge between C-3 and C-6. The biosynthetic pathways for torgranols A-C were proposed. Some compounds displayed antimicrobial activities against Mycobacterium tuberculosis and/or Staphylococcus aureus.

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

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

In Vitro Cytotoxicity and Anti-HIV Activity of Crude Extracts of Croton macrostachyus, Croton megalocarpus and Croton dichogamus

INTRODUCTION

Human immunodeficiency virus (HIV) affects the body's defense mechanisms and leads to a number of opportunistic infections which later cause fatality as a result of an acquired immunodeficiency syndrome (AIDS). More than half a million individuals have lost their life in 2020 due to this disease. Antiretroviral drugs have played a great role in improving the quality of life of HIV infected individuals. The side effects of these drugs coupled with resistance of the virus to the various regimens, necessitates the search for potentially new and effective antiretroviral medication. The objective of this study is to evaluate anti-HIV activity of crude extracts of three Croton plants.

METHODS

As part of our effort in screening anti-HIV medications, we evaluated the cytotoxicity and anti-HIV activity of three Croton species used as herbal medicine in Africa. Crude extracts of Croton macrostachyus, Croton megalocarpus and Croton dichogamus were tested for their replication inhibition activity against laboratory adapted strains HIV-1IIIB in Human T-lymphocytic MT-4 cell line.

RESULTS

Based on our findings, the crude aerial part extract of C. dichogamus displayed the highest anti-HIV activity by inhibiting 73.74% of viral induced cytopathic effect (CPE) at IC50 value of 0.001 + 0.00 μg/mL giving a selectivity index (SI) of 3116.0. In addition, the crude leaf extract of C. megalocarpus showed higher anti-HIV activity by inhibiting 74.65% of CPE at IC50 value of 0.05 + 0.03 μg/mL giving an SI of 571.3.

CONCLUSION

Out of five extracts from three Croton species screened for anti-HIV activity using human T-lymphocytic MT-4 cells, the leaf extract of Croton megalocarpus and aerial part extract of Croton dichogamus could be considered as promising extracts as they display high antiviral activity with low toxicity and high selectivity index values. To investigate the active constituents responsible for the anti-HIV activity, chemical identification of the active constituents is now in progress in our laboratory. Since there is no previously reported anti-HIV activity for these plants, there is a great need to isolate the compounds responsible for the noted activity.

Diterpenoids from the whole plants of Croton yunnanensis and their bioactivities

Four new 19-nor-clerodane diterpenoids (1-4), one new 15,16-dinor-ent-pimarane diterpenoid (5) together with four known diterpenoids (6-9) were isolated from whole plants of Croton yunnanensis. The structures of these compounds were determined by extensive spectroscopic methods including 1D, 2D NMR, HR-ESI-MS, and by comparing their NMR data with those of previously reported compounds. The experimental and calculated electronic circular dichroism data were used to define their absolute configurations. The ¹H and ¹³C NMR spectra of 6 were completely assigned for the first time. All isolated compounds (1-9) were evaluated for their cytotoxic activities against five human cancer cell lines (including SMMC-7721, HL-60, A-549, MCF-7, and SW-480), and anti-inflammatory activities in LPS-induced RAW264.7 macrophages. Crotonyunnan E (5) exhibited selective cytotoxicities against three tumor cell lines, SMMC-7721 (human hepatoma cells, IC₅₀ 4.47 ± 0.39 μM), HL-60 (human premyelocytic leukemia, IC₅₀ 14.38 ± 1.19 μM), and A-549 (human lung cancer cells, IC₅₀ 27.42 ± 0.48 μM), while none of the compounds showed obviously anti-inflammatory activities at 50 μM level.

Sublyratins A-O, Labdane-Type Diterpenoids from Croton sublyratus

Fifteen new labdane-type diterpenoids, sublyratins A-O (1-15), along with four known analogues (16-19) were isolated from the aerial parts of Croton sublyratus. Their structural assignments were challenging due to the stereoisomeric features evident and were achieved by analyzing comprehensively the spectroscopic data and electronic circular dichroism spectra and using X-ray crystallographic analysis. Compounds 9 and 16-18 displayed cytotoxic activity against the HL-60 cell line with IC₅₀ values of 1.5-2.8 μM.

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

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

ent-Clerodane diterpenoids from the stems of Croton krabas

The first phytochemical investigation from the stems of Croton krabas resulted in the isolation of three new ent-clerodane diterpenoids, crotonkrabases A-C (1-3), along with two known compounds, 12-oxohardwickiic acid (4) and crotonpyrone B (5). Their structures were elucidated using extensive spectroscopic methods. The structure of 3 was unambiguously proven by X-ray crystallography. Furthermore, the absolute configurations of compounds 1-3 were identified by NOESY and the comparison of their experimental ECD spectra with those of calculated ECD spectra reported in the literature. Compounds 1, 2, and 5 showed antibacterial activities against two Gram-positive bacteria (Bacillus cereus and Bacillus subtilis); whereas compound 4 exhibited weak antibacterial against B. cereus. In addition, compound 4 showed potent α-glucosidase inhibitory activity, which was lower than the reference standard acarbose.

Bioactive terpenoids from Croton laui

Two new highly-oxygenated neo-clerodane diterpenoids, 3S-acetoxyl-mollotucin D dilactone ester (1) and 6S-crotoeurin C (2), and a new lupane-type triterpene, 16β-hydroxyl-3β-O-trans-coumaroyl-betulin (6), as well as three known analogues (3-5) were obtained from the leaves of Croton laui. The structures of the new compounds were determined by extensive spectroscopic methods, and their absolute configurations were determined by combination of single-crystal X-ray diffraction analysis, electronic circular dichroism (ECD) spectra, and literature data. Compounds 2 and 3 exhibited inhibitory activities of lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages with IC₅₀ values of 1.2 and 1.6 μM, respectively. Additionally, compound 6 exhibited activity against Col205 and HepG2 cell lines with IC₅₀ values of 12.9 and 17.7 μM, respectively.

Laevifins A-G, clerodane diterpenoids from the Bark of Croton oblongus Burm.f

A phytochemical investigation of the stem barks of the Malaysian Croton oblongus Burm.f. (Syn. Croton laevifolius Blume) (Euphorbiaceae) yielded seven previously undescribed ent-neo-clerodane diterpenoids, laevifins A - G and the known crovatin (3). Structures were established by a combination of spectroscopic methods including HRESIMS, NMR spectroscopy and X-ray crystallography. The absolute configuration of crovatin and laevifins A-G was established by comparison of experimental ECD and theoretical TDDFT ECD calculated spectra. This is the first report on the occurrence of the sesquiterpenoid cryptomeridiol in a Croton species. In vitro cytotoxicity assays on laevifins A, B and G showed moderate activities against the MCF-7 cancer cell line (IC₅₀ 102, 115 and 106 μM, respectively) while β-amyrin and acetyl aleuritolic acid showed good anti-inflammatory activity on the LPS-induced NF-κB translocation inhibition in RAW 264.7 cells assay with IC₅₀ values of 23.5 and 35.4 μg/mL, respectively.

Chemical Constituents from Croton Species and Their Biological Activities

The genus Croton belongs to the Euphorbiaceae family, which comprises approximately 1300 species. Many Croton species have been used as folk medicines. This review focuses on the chemical constituents from Croton species and their relevant biological activities, covering the period from 2006 to 2018. A total of 399 new compounds, including 339 diterpenoids, were reported. Diterpenoids are characteristic components of the Croton species. These isolated compounds exhibited a broad spectrum of bioactivities, including cytotoxic, anti-inflammatory, antifungal, acetylcholinesterase inhibitory, and neurite outgrowth-promoting properties. The present review provides a significant clue for further research of the chemical constituents from the Croton species as potential medicines.

Ent-Clerodane Diterpenes from the Bark of Croton oligandrus Pierre ex Hutch. and Assessment of Their Cytotoxicity against Human Cancer Cell Lines

New clerodane diterpenes, 12-epi-megalocarpodolide D (2) and an epimeric mixture of crotonolins A (3) and B (4), were isolated from the bark of Croton oligandrus following a bioassay-guided isolation protocol. Known compounds, megalocarpodolide D (1), 12-epi-crotocorylifuran (5), cluytyl-ferulate (6), hexacosanoyl- ferulate (7), vanillin (8), acetyl-aleuritolic acid (9) and lupeol (10), were also isolated. The structures of the isolated compounds (1–10) were elucidated by spectroscopic means. The cytotoxicity of compounds 1–10 was assessed against A549, MCF7, PC3 and PNT2 cell lines using the MTT assay. Compounds 1 and 2 showed moderate levels of activity against both A549 and MCF7 cells with 1 being the most active with IC₅₀ values of 63.8 ± 13.8 and 136.2 ± 22.7 µM against A549 and MCF7 cells, respectively. The epimeric mixture of 3 and 4 was moderately active against A549 and PC3 cells (IC₅₀ = 128.6 ± 31.0 and 111.2 ± 2.9 µM, respectively).

Biological screening of extracts from leaf and stem bark of Croton floribundus Spreng. (Euphorbiaceae)

Abstract This work describes the preliminary evaluation of cytotoxic, antimicrobial, molluscicidal, antioxidant and anticholinesterase activities from leaf (LECF) and stem bark alcoholic extracts (BECF) of the species Croton floribundus Spreng. (Euphorbiaceae), popularly known as capixingui or tapixingui. BECF presented significant toxicity (LC50 = 89.6 μg/ml) in the Artemia salina Leach, 1819 (Crustacea: Branchiopoda) bioassay, whereas LECF did not show activity (LC50 > 1000 μg/ml). From DPPH method, the values of IC50 for the LECF and BECF were 61.2 μg/ml and 62.2 μg/ml, respectively, showing that C. floribundus has an expressive antioxidant activity. Antimicrobial susceptibility was evaluated by microdilution technique and only BECF was active against Staphylococcus aureus (MIC = 39.6 μg/ml). The extracts did not present molluscicidal activity against snail Biomphalaria glabrata Say, 1818 (Gastropoda: Planorbidae). Both extracts revealed the presence of several components with an inhibiting capacity of acetylcholinesterase enzyme on the bioautographic assay. C. floribundus showed to be a promising species considering that it exhibited good biological activity in the most assays performed.

Cascarinoids A-C, a Class of Diterpenoid Alkaloids with Unpredicted Conformations from Croton cascarilloides

Cascarinoids A-C (1-3), a new class of diterpenoid alkaloids with unpredicted conformations, were isolated and structurally characterized from Croton cascarilloides. It was demonstrated that the dispersion interaction might be one of the main contributors that stabilized the folded conformations for compounds 1-3. Compounds 2 and 3 showed moderate immunosuppressive activity against T and/or B lymphocyte cells.

Norcrassin A, a novel C16 tetranorditerpenoid, and bicrotonol A, an unusual dimeric labdane-type diterpenoid, from the roots of Croton crassifolius

Norcrassin A (1), a novel C₁₆ tetranorditerpenoid, featuring a new carbon skeleton, and bicrotonol A (2), an unusual dimeric labdane-type diterpenoid, were isolated from Croton crassifolius.

Bioactive diterpenoids from Croton laevigatus

Eight previously undescribed diterpenoids, crolaevinoids A-H, including two halimanes, four clerodanes, and two laevinanes, along with six known analogues were isolated from the twigs of Croton laevigatus. The structures of the previously undescribed were elucidated by spectroscopic analysis, and their absolute configurations were determined by combination of a single crystal X-ray diffraction and CD analysis (exciton chirality and Rh₂(OCOCF₃)₄-induced methods). Crolaevinoids A and B represent the first halimane diterpenoids with a unique lactone bridge between C-12 and C-17. All compounds were evaluated for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW264.7 macrophage cells. Furocrotinsulolide A and 3,4,15,16-diepoxy-cleroda-13(16),14-diene-12,17-olide exhibited pronounced inhibition of NO production with IC₅₀ values of 10.4 ± 0.8 and 6.0 ± 1.0 μM, respectively, being more potent than the positive control, quercetin (IC₅₀ = 13.1 ± 1.9 μM).

Diterpenoids from the roots of Croton dichogamus Pax

Four previously undescribed diterpenoids including two crotofolanes, crotodichogamoin A and B, and two halimanes, crothalimene A and B, a new sesquiterpenoid, and fifteen previously reported compounds, including the crotofolane, crotohaumanoxide, the casbane, depressin, a further seven furanohalimane diterpenoids, three patchoulane and two further cadinane sesquiterpenoids and aleuritolic acid were isolated from the root of Croton dichogamus. Crotodichogamoin B is an important biosynthetic intermediate of the crotofolane class and this is the first report of patchoulene sesquiterpenoids from the genus. Compounds were tested at one concentration, 1 × 10^-5 M, in the NCI59 cell one-dose screen but did not show significant activity snd were also evaluated for their cytotoxicity against Caco-2 cell lines using the neutral red assay. 10-epi-Maninsigin D reduced Caco-2 cell viability at 10, 30 and 100 μM, with values of decreased viability of 28%, 48% and 43% respectively. None of the other tested compounds showed significant activity.

Clerodane Diterpenoid Glucosides from the Stems of Tinospora sinensis

Ten new clerodane diterpenoid glucosides (1-10) and three known analogues (11-13) were isolated from an EtOAc extract of the stems of Tinospora sinensis. Spectroscopic analyses and chemical methods were used to elucidate the structures of these isolates. The absolute configurations of tinosinenosides A-C (1-3) were established by using experimental and calculated ECD data. Their cytotoxicity against the human epithelioid cervical carcinoma (HeLa) cell line and the nitric oxide production inhibitory activity of lipopolysaccharide-activated N9 microglial cells were tested. 1-Deacetyltinosposide A (12) exhibited mild cytotoxicity against HeLa cells, with an IC₅₀ value of 8.35 ± 0.60 μM.

Clerodane diterpenes: sources, structures, and biological activities

Covering: 1990 to 2015The clerodane diterpenoids are a widespread class of secondary metabolites and have been found in several hundreds of plant species from various families and in organisms from other taxonomic groups. These substances have attracted interest in recent years due to their notable biological activities, particularly insect antifeedant properties. In addition, the major active clerodanes of Salvia divinorum can be used as novel opioid receptor probes, allowing greater insight into opioid receptor-mediated phenomena, as well as opening additional areas for chemical investigation. This article provides extensive coverage of naturally occurring clerodane diterpenes discovered from 1990 until 2015, and follows up on the 1992 review by Merritt and Ley in this same journal. The distribution, chemotaxonomic significance, chemical structures, and biological activities of clerodane diterpenes are summarized. In the cases where sufficient information is available, structure activity relationship (SAR) correlations and mode of action of active clerodanes have been presented.

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, 2014 is reviewed.

Enantioselective synthesis of decalin structures with all-carbon quaternary centers via one-pot sequential Cope/Rauhut-Currier reaction

The first example of one-pot sequential Cope/Rauhut-Currier reactions are reported and used to make functionalized decalin structures with all-carbon quaternary stereocenters. The substrates for the new sequential reaction are generated through a six-step sequence including an enantioselective Birch reduction-allylation reaction which makes the overall process asymmetric.