Diterpenoids from the twigs and leaves of Croton caudatus var. tomentosus

Labdane and ent-halimane diterpenoids with STAT3-inhibitory activity from Leonurus sibiricus

Nine undescribed labdane diterpenoids (1-9) and one undescribed ent-halimane diterpenoid (10) were isolated from the aerial parts of Leonurus sibiricus, together with four known analogues (11-14) during our searching for naturally occurring antitumor agents. Their structures were established by detailed spectroscopic analyses and electronic circular dichroism analysis. Compound 4 possessed a rare 10-epi labdane scaffold. All compounds except 5 were evaluated for their inhibitory activities against interleukin (IL)-6-stimulated signal transducer and activator of transcription (STAT3) expression using a luciferase reporter assay. Compound 1 showed the most inhibitory effect with the IC50 value 20.31 μM. Compound 1 inhibited the activation of JAK2/STAT3 signal pathway through binding to Gln326 of STAT3 in CNE cells. The antiproliferative evaluation of compound 1 against CNE, CAL-27, A549 and PANC-1 cells demonstrated that CNE cells were the most sensitive to 1. Furthermore, compound 1 showed moderate efficacy in inhibiting cell migration, invasion, and epithelial-mesenchymal transition in CNE cells. In addition, compound 1 also promoted ferroptosis in CNE cells in a dose-dependent manner. These results suggest that compound 1 might be a potential candidate lead for treating nasopharyngeal carcinoma.

Crotofolane Diterpenoids and Other Constituents Isolated from Croton kilwae

Six new crotofolane diterpenoids (1-6) and 13 known compounds (7-19) were isolated from the MeOH-CH2Cl2 (1:1, v/v) extracts of the leaves and stem bark of Croton kilwae. The structures of the new compounds were elucidated by extensive analysis of spectroscopic and mass spectrometric data. The structure of crotokilwaepoxide A (1) was confirmed by single-crystal X-ray diffraction, allowing for the determination of its absolute configuration. The crude extracts and the isolated compounds were investigated for antiviral activity against respiratory syncytial virus (RSV) and human rhinovirus type-2 (HRV-2) in HEp-2 and HeLa cells, respectively, for antibacterial activity against the Gram-positive Bacillus subtilis and the Gram-negative Escherichia coli, and for antimalarial activity against the Plasmodium falciparum Dd2 strain. ent-3β,19-Dihydroxykaur-16-ene (7) and ayanin (16) displayed anti-RSV activities with IC50 values of 10.2 and 6.1 μM, respectively, while exhibiting only modest cytotoxic effects on HEp-2 cells that resulted in selectivity indices of 4.9 and 16.4. Compounds 2 and 5 exhibited modest anti-HRV-2 activity (IC50 of 44.6 μM for both compounds), while compound 16 inhibited HRV-2 with an IC50 value of 1.8 μM. Compounds 1-3 showed promising antiplasmodial activities (80-100% inhibition) at a 50 μM concentration.

Two highly oxygenated nor-clerodane diterpenoids from Croton caudatus

Two highly oxygenated nor-clerodane diterpenoids, crocleropenes A and B (1 and 2), together with four known compounds (3-6) were isolated from the leaves and twigs of Croton caudatus. Their structures were elucidated by combination of extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. 1 and 2 represent the first examples of nor-clerodane-3,5(10)-diene diterpenoids. Compounds 1 and 2 exhibited weak cytotoxicity in vitro against MCF-7 cancer cells with IC₅₀ values of 35.8 and 40.2 μM, respectively. [Formula: see text].

Oxygenated Geosmins and Plant-like Eudesmanes from a Bacterial Mangrove Endophyte

Geosmin (1) is a microbial terpene metabolite that is responsible for the typical smell of soil and causes an off-odor of food and water. Eudesmane sesquiterpenes are commonly found in plant essential oils. Here we describe the discovery of four geosmin-type metabolites, 7R-hydroxygeosmin (2), 3-oxogeosmin (3), 2R-hydroxy-7-oxogeosmin (4), 5-deoxy-7β,9β-dihydroxygeosmin (5), the plant-like eudesmanes 4β,10α-eudesmane-5β,11-diol (6) and (1S,5S,6S,7S,10S)-10α-eudesm-4(15)-ene-1α,6α-diol (7), and the known 1(10)E,5E-germacradiene-2,11-diol (8) from a bacterial endophyte (Streptomyces sp. JMRC:ST027706) of the mangrove plant Bruguiera gymnorrhiza. By means of NMR, MS, and ECD spectroscopy, all chemical structures as well as the absolute configurations for the new compounds were elucidated. Compounds 2-5 represent the first geosmin-related metabolites directly as bacterial natural products. The plant-derived eudesmane-5β,11-diol (6) and (1S,5S,6S,7S,10S)-10α-eudesm-4(15)-ene-1α,6α-diol (7) are also now reported as bacterial products. The broad antimicrobial activities of 6 against a suite of fungal and bacterial pathogens including methicillin-resistant Staphylococcus aureus suggest that this terpene could be an important active principle of the medicinal plant Cymbopogon distans. The discovery of geosmin metabolites from one actinomycete indicated that these bacteria could possess enzymes for modifying geosmin and offer a possibility for bioremediation.

Anti-Migratory and Pro-Apoptotic Properties of Parvifloron D on Triple-Negative Breast Cancer Cells

Medicinal plants are important sources of new bioactive compounds with potential anticancer activity. Parvifloron D (ParvD) is an abietane diterpenoid, isolated in high amounts from Plectranthus ecklonii Benth. Previous reports have suggested potential therapeutic properties for ParvD. ParvD has shown pro-apoptotic and cytotoxic effects in leukemia and melanoma cell lines. However, to the best of our knowledge, there are no studies in triple-negative breast cancer (TNBC) models. TNBC is a breast cancer subtype characterized by an aggressive behavior with poor clinical outcomes and weak overall therapeutic responses to the current treatment options. This work aimed at evaluating the anticancer effect of ParvD in MDA-MB-231 cells, a model of human TNBC. To obtain sufficient amounts of purified ParvD the efficiency of several extraction methods was compared. ParvD (0.1–10 µM) decreased cell viability in a concentration-dependent manner. Treatment with ParvD (5 µM) significantly increased the percentage of apoptotic nuclei and exposure to 3 µM ParvD increased the sub-G1 population. Since altered cell adherence, migration, and invasion are determinant processes for the formation of metastases, the effect of ParvD on these cellular processes was tested. Although treatment with ParvD (1 µM) had no effect on cell-substrate attachment, ParvD (1 µM) significantly reduced cell chemotaxis and invasion. This is the first report describing the proapoptotic effect of ParvD in TNBC cells. Moreover, for the first time we have shown that ParvD reduces cell motility, unraveling potential anti-metastatic properties.

Naturally occurring of α,β-diepoxy-containing compounds: origin, structures, and biological activities

Diepoxy-containing compounds are widely distributed in nature. These metabolites are found in plants and marine organisms and are also produced by many microorganisms, fungi, or fungal endophytes. Many of these metabolites are antibiotics and exhibit a wide variety of biological activities. More than 80 α,β-diepoxy-containing compounds are presented in this article, which belong to different classes of chemical compounds including lipids, terpenoids, alkaloids, quinones, hydroquinones, and pyrones. The main activities that characterize α,β-diepoxy-containing compounds are antineoplastic with confidence up to 99%, antifungal with confidence up to 94%, antiinflammatory with confidence up to 92%, or antibacterial with confidence up to 78%. In addition, these metabolites can be used as a lipid metabolism regulator with a certainty of up to 81%, antiviral (Arbovirus) activity with a certainty of up to 71%, or antiallergic activity with confidence up to 69%. These data on the biological activity of diepoxy-containing compounds are of considerable interest to pharmacologists, chemists, and medical professionals who are involved in phytomedicine and related areas of science and industry.

A Pair of Enantiomeric Bis- seco-abietane Diterpenoids from Cryptomeria fortunei

(±)-Cryptomeriolide, a pair of racemic bis- seco-abietane diterpenoids, were isolated from the bark of Cryptomeria fortunei. The separation of enantiomers was achieved by using chiral stationary phase HPLC. Their structures including the absolute configuration and conformations in solution and solid state were determined by extensive analysis of spectroscopic data, single-crystal X-ray diffraction, and comparison of calculated and experimental electronic circular dichroism data. A bioinspired one-pot enantiomeric synthesis of 1a and 1b was accomplished via a readily made intermediate orthoquinone from sugiol. All compounds including the synthetic intermediates were assayed for their cytotoxic activities on human cancer cell lines HL-60, A549, and SGC7901.

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.

Phytochemical Study of Salvia leriifolia Roots: Rearranged Abietane Diterpenoids with Antiprotozoal Activity

Phytochemical investigation of the lipophilic extract of the roots of Salvia leriifolia resulted in the isolation of the new rearranged abietane diterpenoids leriifoliol (1) and leriifolione (2), together with 10 known diterpenoids. Structure elucidations were performed via extensive NMR and HRESIMS data, and the absolute configurations of compounds 1 and 3-5 were established by evaluation of experimental and calculated ECD spectra. The antiplasmodial activity of the new isolates was assayed against Trypanosoma brucei rhodesiense, T. cruzi, Plasmodium falciparum, and Leishmania donovani and also toxicity against rat myoblast (L6) cells. Compound 1 displayed antimalarial and low cytotoxic activity with IC₅₀ values of 0.4 and 33.6 μM, respectively, and a selectivity index of 84. Compound 2 displayed activity against T. brucei, T. cruzi, and L. donovani, with IC₅₀ values of 1.0, 4.6, and 1.0 μM, respectively. Putative biosynthetic pathways toward the formation of 1, 2, and 3 are proposed. Leriifoliol (1) is the first 20- nor-9,10- seco-abietane, while 2 exhibits an uncommon 6-6-5 fused-ring system.

Halimane diterpenoids: sources, structures, nomenclature and biological activities

Diterpenes with a halimane skeleton constitute a small group of natural products that can be biogenetically considered as being between labdane and clerodane diterpenoids.

Roscotanes and roscoranes: Oxygenated abietane and pimarane diterpenoids from Kaempferia roscoeana

Eight previously undescribed ditepenoids, including four oxygenated abietanes (roscotanes A-D) and four oxygenated pimaranes (roscoranes A-D), along with twelve known diterpenoids were isolated from the whole plants of Kaempferia roscoeana. Their structures were elucidated by extensive spectroscopic analysis, and the structure of roscotane A was further confirmed by single crystal X-ray diffraction analysis. Most isolated compounds were evaluated for their antimicrobial and antimalarial activities.