Labdane-type Diterpenes Research Articles

Pesticide and antimicrobial evaluation of three labdane-type diterpenes, and one flavonoid glycoside, isolated from rhizomes of Hedychium coronarium J. Koenig

Three labdane-type diterpenes, namely coronalactoside I, hedychilactone A, and (E)-labda-8(17),12-dien-15(16)-olide, along with the flavonoid glycoside Isolinariin A, were isolated from Heydichium coronarium. Structural elucidation employed spectroscopic techniques (IR, MS, NMR, and DEPT) and comparison with literature data. Pesticidal and antimicrobial activities were assessed. Isolinariin A exhibited potent nematicidal activity (71.33% mortality) against Meloidogyne incognita, while Coronalactoside I demonstrated strong inhibition of nematode egg hatchability (26.00% at 1 µg/mL). In insecticidal activity against Spodoptera litura, (E)-labda-8(17),12-dien-15(16)-olide displayed significant mortality (93.66% at 100 µg/mL). Molecular docking studies indicated favourable interactions with target proteins, suggesting potential in pest management. These findings propose the application of these compounds to mitigate the ecological impact of synthetic pesticides.

Cytotoxic Labdane Diterpenes, Norlabdane Diterpenes and Bis-Labdanic Diterpenes from the Zingiberaceae: A Systematic Review.

Over the years, labdane diterpenes, norlabdane diterpenes, and bis-labdanic diterpenes with cytotoxic activities have been identified across various families in the plant kingdom including the Zingiberaceae. The present review discusses the distribution of these labdane-type diterpenes within the Zingiberaceae; their extraction, isolation, and characterization from the respective Zingiberaceae species; the structural similarities and differences within each group and between the different groups of the labdane-type diterpenes; and their cytotoxic activities against breast, cervical, liver, colorectal, pancreatic, lung and prostate cancer cell lines. The review will also provide insight into how the cytotoxic activities of the labdane-type diterpenes are influenced by their structural features.

Labdane-type Diterpenes from Pinus eldarica Needles and Their Anti-Helicobacter pylori Activity.

Pinus eldarica is a medicinal tree used in traditional herbal medicine for the treatment of bronchial asthma and various skin diseases. As part of our ongoing search for bioactive phytochemicals with novel structures in natural products, we performed a phytochemical analysis of the methanol (MeOH) extract from P. eldarica needles collected in Iran. Phytochemical investigation of the MeOH extract, aided by liquid chromatography–mass spectrometry-based analysis, resulted in the isolation and identification of three labdane-type diterpenes (1–3), including a new and relatively unique norlabdane-type diterpene with a peroxide moiety, eldaricoxide A (1). The chemical structures of the isolated labdane-type diterpenes were elucidated by analyzing the spectroscopic data from 1D and 2D NMR and high-resolution electrospray ionization-mass spectrometry. The absolute configuration of eldaricoxide A (1) was established by employing a computational method, including electronic circular dichroism calculation and specific optical rotation. An anti-Helicobacter pylori test was conducted, where compound 3 exhibited the most potent antibacterial activity against H. pylori strain 51, inducing 72.7% inhibition (MIC50 value of 92 μM), whereas eldaricoxide A (1) exhibited moderate antibacterial activity against H. pylori strain 51, inducing 54.5% inhibition (MIC50 value of 95 μM). These findings demonstrated that the identified bioactive labdane-type diterpenes 1 and 3 can be applied in the development of novel antibiotics against H. pylori for the treatment of gastric and duodenal ulcers.

Bioactivity-guided identification and isolation of a major antimicrobial compound in Cistus creticus subsp. creticus leaves and resin “ladano”

Cistus creticus subsp. creticus is a shrubby Mediterranean plant used since ancient times in folk medicine for the treatment of different diseases. C. creticus extracts and resin contain different types of secondary metabolites, such as terpenoids (predominantly labdane type diterpenoids), and phenylpropanoids. Growth conditions seem to influence the content of labdane-type diterpenes and flavan-3-ols in leaves of C. creticus subsp. creticus. Histochemical staining of leaves’ trichomes and comprehensive phytochemical characterization of resin, leaves and their exudates, indicated that long-stalked capitate trichomes of C. creticus subsp. creticus, grown both in vitro (IV) and in greenhouse (GH), are capable of producing bioactive oleoresin-related terpenoids and phenylpropanoids compounds. Bioactivity-guided approach was implemented in search for the major antibacterial compound in C. creticus resin against two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive bacteria (Bacillus cereus and Micrococcus flavus). Bioautographic assay on TLC plates with separated components of Cistus resin extract, revealed a pronounced zone of microbial growth inhibition, corresponded to a highly active compound with Rf values of 0.45, structurally characterized and identified as ent-3β-acetoxy-13-epi-manoyl oxide. This finding opens the route for focusing on isolation and functional characterization of genes involved in the biosynthesis of ent-3β-acetoxy-13-epi-manoyl oxide and its precursor ent-3β-hydroxy-13-epi-manoyl oxide, with the aim to establish sustainable in vitro biotechnological protocols for its large-scale production in homologous and heterologous plant and microbial hosts.

Alpha-amination of labdane-type diterpenes by organocatalysis

The first electrophilic α-amination reaction of labdane-type diterpene (−)-(5S,9S,10S,13S)-labd-7-en-15-oic acid and (+)-(5S,8R,9R,10S,13R)-8-hydroxylabdan-15-oic acid, isolated from aerial parts of Ageratina jocotepecana is presented. In the presence of dibenzylazodicarboxylate and proline followed by an in situ reduction, the corresponding hydrazino alcohols were obtained. It is demonstrated that the first diterpene moiety had no influence in the diastereoselectivity that is then controlled by the catalyst used, at the opposite to the second diterpene that mainly control the diastereochemistry of the product.

Plant Disease Control Efficacy of Platycladus orientalis and Its Antifungal Compounds.

Plants contain a number of bioactive compounds that exhibit antimicrobial activity, which can be recognized as an important source of agrochemicals for plant disease control. In searching for natural alternatives to synthetic fungicides, we found that a methanol extract of the plant species Platycladus orientalis suppressed the disease development of rice blast caused by Magnaporthe oryzae. Through a series of chromatography procedures in combination with activity-guided fractionation, we isolated and identified a total of eleven compounds including four labdane-type diterpenes (1–4), six isopimarane-type diterpenes (5–10), and one sesquiterpene (11). Of the identified compounds, the MIC values of compounds 1, 2, 5 & 6 mixture, 9, and 11 ranged from 100 to 200 μg/mL against M. oryzae, whereas the other compounds were over 200 μg/mL. When rice plants were treated with the antifungal compounds, compounds 1, 2, and 9 effectively suppressed the development of rice blast at all concentrations tested by over 75% compared to the non-treatment control. In addition, a mixture of compounds 5 & 6 that constituted 66% of the P. orientalis ethyl acetate fraction also exhibited a moderate disease control efficacy. Together, our data suggest that the methanol extract of P. orientalis including terpenoid compounds has potential as a crop protection agent.

The Cyr61 Is a Potential Target for Rotundifuran, a Natural Labdane-Type Diterpene from Vitex trifolia L., to Trigger Apoptosis of Cervical Cancer Cells.

Cervical cancer is a common female malignant tumor that seriously threatens human health. This study explored the anticervical cancer effects and potential mechanisms of Rotundifuran (RTF), a natural product isolated from Vitex trifolia L. In this study, we found that RTF can suppress the proliferation of cervical cancer cell lines, including HeLa and SiHa cells (with the IC50 less than 10 μM), via induction of apoptosis in vitro, and the antitumor effect of RTF is further confirmed on the HeLa cell-inoculated xenograft model. In addition, our results proved that the antitumor effects of RTF might be related with the reactive oxygen species- (ROS-) induced mitochondrial-dependent apoptosis through MAPK and PI3K/Akt signal pathways. Using proteomics analysis and the drug affinity responsive target stability- (DARTS-) combined mass spectrometry (DARTS-MS), Cyr61 was indicated as a potential target for RTF in cervical cancer cells. Our present study would be beneficial for the development of RTF as a candidate for treatment of cervical cancer in the future.

Labdane-Type Diterpenes from the Aerial Parts of Rydingia persica: Their Absolute Configurations and Protective Effects on LPS-Induced Inflammation in Keratinocytes.

Phytochemical investigations of an extract of the aerial parts of Rydingia persica led to the isolation of 14 labdane-type diterpenoids, of which compounds 1–5, 8, and 12–14 turned out to be new natural products, while the remaining compounds were isolated for the first time from the genus Rydingia. Their structures were elucidated using 1D- and 2D-NMR and mass spectrometry, and their absolute configurations were determined by quantum chemical calculation methods. Furthermore, DP4+ NMR chemical shift probability calculations were performed for compounds 12–14, in order to elucidate the orientation of the ambiguous chiral center at C-15, prior to absolute configuration determination. The methanol extract of the aerial parts of R. persica along with subfractions obtained and selected isolated compounds were evaluated for their effects on inflammation-related factors such as nitrotyrosine formation, IL-6 release, and TNF-α release, along with tight-junction proteins claudin-1 and occludin expression in LPS-stimulated HaCaT cells. Occludin and claudin-1 are tight-junction proteins, which play a pivotal role in wound repair mechanisms. Overall, the subfractions and compounds isolated showed moderate to high activity, indicating that labdane-type diterpenoids contribute to the anti-inflammatory and wound-healing activity of R. persica.

The old pharmaceutical oleoresin labdanum of Cistus creticus L. exerts pronounced in vitro anti-dengue virus activity

Ethnopharmacological relevanceThe haemorrhagic dengue fever affects up to 500 million patients, annually causing 20.000 deaths, with no chemotherapeutic agent available. The oleoresin labdanum of Cistus creticus L. has been established as an anti-infective agent since antiquity in Mediterranean ethnopharmacology. Materials and methodsWe tested several extracts and fractions of labdanum - standardised on labdane-type diterpenes via GC-MS - on their activity against the dengue virus (DENV-2 strain 00st-22A) in in vitro Vero cell cultures (96-well-plates, 5 days). Preliminary experiments with a labdanum diethyl ether raw-extract did not yield measureable results due to cytotoxic effects against Vero cells. In all following experiments, cell viability was constantly checked using the MTT-test. Fractionation of this raw-extract by liquid-liquid-extraction and column-chromatography on silica-gel (gradient elution with hexane, EtOAc, CHCl3, MeOH) succeeded in separating the anti-viral activity of labdanum from its cytotoxic effect. ResultsIn the most active fraction GS5 at 30 μg/ml, dengue virus proliferation was 100% suppressed and cell viability was over 90%. Structural elucidation of major constituents of GS5 is currently ongoing, but thin-layer chromatography showed that this fraction is mainly dominated by manoyloxides, a class of labdane-type diterpenes with known antimicrobial activity. Claims concerning the antiviral activity of above ground parts of C. creticus have been made previously, but these generally ascribe this activity to hot water soluble polyphenols and propose an unspecific tanning effect of the viral surface proteins as the mechanism of action. However, the water soluble fraction enhanced viral proliferation. ConclusionWe therefore describe a direct, pharmacological, antiviral activity of a diethyl ether extract of labdanum against a virulent haemorrhagic fever like dengue for the first time.

Volatile Chemical Composition, Antibacterial and Antifungal Activities of Extracts from Different Parts of Globba schomburgkii Hook.f.

Globba schomburgkii Hook.f. is an ornamental plant that has recently found increasing demand as cut flowers, hence generating a significant number of by-products from different parts of the plant. To investigate the further applications of these by-products, twelve crude extracts from rhizomes, stalks, leaves, and flowers were prepared by serial exhaustive extraction. The volatile composition of these extracts was analyzed by GC/MS; a total of 89 compounds were identified, most of which were sesquiterpenes as well as some labdane-type diterpenes. The antimicrobial activities of these extracts were evaluated, revealing a correlation between the terpenoid content and antibacterial activities. Notably, the dichloromethane extracts of rhizomes and flowers, which contained the highest amount of terpenoids (e. g., α-gurjunene, guaia-9,11-diene, γ-bicyclohomofarnesal, β-caryophyllene, and caryophyllene oxide), displayed the most prominent antibacterial activities. This work demonstrates the potential use of the crude extracts from G. schomburgkii as natural antibacterial ingredients for pharmaceutical and other applications.

Sclareol-loaded hyaluronan-coated PLGA nanoparticles: Physico-chemical properties and in vitro anticancer features.

Sclareol (labd‑14‑ene‑8,13‑diol), a phytochemical compound belonging to labdane-type diterpenes, has recently attracted noteworthy attention because of its peculiar pharmacological properties. The foremost obstacle to an efficacious application and use of this molecule is its unfavorable bioavailability due to its poor aqueous solubility. In this investigation sclareol was encapsulated within PLGA nanoparticles with the aim of favoring its administration in physiological media, increasing its anticancer activity and obtaining a stable colloidal formulation. These nanoparticles containing sclareol were characterized by a mean diameter of 100-150 nm, a narrow size distribution and a negative surface charge. The active compound was efficiently retained by the polymeric structure and did not induce any physical destabilization. The coating of the PLGA nanoparticles with hyaluronic acid (1.5 MDa) increased the antitumor efficacy of the encapsulated drug against human breast cancer cells expressing the hyaluronan receptors (MCF-7 and MDA-MB468) while a similar pharmacological effect was obtained on human colon carcinoma cells (CaCo-2). CLSM analysis demonstrated the intracellular localization of fluorescent nanosystems after 3 h incubation.

Identification of antimicrobial volatile compounds produced by the marine bacterium Bacillus amyloliquefaciens strain S13 newly isolated from brown alga Zonaria tournefortii

ABSTRACTThe present work focuses on the production and identification of microbial volatile organic compounds (VOCs) associated with antimicrobial properties from Bacillus amyloliquefaciens strain S13 newly isolated from the brown alga Zonaria tournefortii. For this purpose, strain isolated was grown on Luria–Bertani culture medium with 15‰ (w/v) NaCl, with an initial pH 7.2 at 30°C for 48 h under continuous agitation at 180 rpm. The VOCs were sequentially extracted from the supernatant containing extracellular compounds by hydrodistillation using a Clevenger apparatus and analyzed by gas chromatography-mass spectrometry. The main volatile compounds identified are 13-epi-manoyl oxide (29.39%), manool (17.39%), 15,16-dinorlabd-8(20)-en-13-one (13.17%), labda-8(17),13Z-dien-15-ol (9.51%) and 3α-hydroxy-13-epi-manoyl oxide (5.26%) belonging to the labdane-type diterpenes class. Other compounds representing different chemical classes were also identified in the chemical composition. The produced volatile fraction was tested in vitro on antimicrobial activity and their minimum inhibitory concentration (MIC) values against pathogenic microorganisms were estimated. The results indicated that among the tested microorganisms, Saccharomyces cerevisiae (24 ± 0.3 mm; MIC = 64 μg/mL) was the most susceptible to volatile fraction followed by Agrobacterium tumefaciens (20 ± 0.5 mm; MIC = 128 μg/mL) and Bacillus subtilis (18 ± 0.8 mm; MIC = 128 μg/mL).

Electrospray ionization tandem mass spectrometry of labdane-type acid diterpenes.

Copaifera (Leguminoseae) species produce a commercially interesting oleoresin that displays several biological activities, including antimicrobial and anti-inflammatory properties. Labdane-type diterpenes are the main chemical constituents of these oleoresins, and copalic acid is the only compound that has been detected in all Copaifera oleoresins. In this study, we investigate some aspects of the gas-phase fragmentation reactions involved in the formation of the product ions from the deprotonated compounds (-)-ent-copalic acid (1), (-)-ent-3β-hydroxy-copalic acid (2), (-)-ent-3β-acetoxy-copalic acid (3), and (-)-ent-agathic acid (4) by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and multiple stage mass spectrometry (MSn ). Our results reveal that the product ion with m/z 99 is common to all the analyzed compounds, whereas the product ion with m/z 217 is diagnostic for compounds 2 and 3. Moreover, only compound 4 undergoes CO2 (44 u) and acetic acid (60 u) elimination from the precursor ion. Thermochemical data obtained by computational chemistry at the B3LYP/6-31G(d) level of theory support the proposed ion structures. These data helped us to identify these compounds in a crude commercial Copaifera langsdorffii oleoresin by selective multiple reaction monitoring (MRM). Finally, a precursor ion scan (PIS) strategy aided screening of labdane-type acid diterpenes other than 1 to 4 in the same Copaifera oleoresin sample and led us to propose the structures of 8,17-dihydro-ent-agathic acid (5) and 3-keto-ent-copalic acid (6), which have not been previously reported in Copaifera oleoresins.

Anti-inflammatory diterpenes from the fruits of Vitex trifolia L. var. simplicifolia Cham

Two new labdane-type diterpenes, named viterotulin C (1) and vitexilactone D (2), together with five known diterpenes (3–7), were isolated from the fruits of Vitex trifolia L. var. simplicifolia Cham. Their structures were elucidated by detailed analysis of spectroscopic data. All the compounds were evaluated for their inhibitory effects on nuclear factor-kappa B (NF-κB) pathway in HEK 293 cell line. These compounds presented inhibition on TNF-α-induced NF-κB activation, with inhibition rates ranging from 42.52 ± 10.69% to 68.86 ± 10.76% at the concentration of 50 μM.

Labdane-Type Diterpenes, Galangalditerpenes A-C, with Melanogenesis Inhibitory Activity from the Fruit of Alpinia galanga.

In our continuing study of biologically active natural products from the fruit of Alpinia galanga (Zingiberaceae), we newly isolated three new labdane-type diterpenes, termed galangalditerpenes A–C (1–3), along with four known sesquiterpenes (4–7) and two diterpenes (8 and 9). The stereostructures of 1–3 were elucidated on the basis of their spectroscopic properties. The melanogenesis inhibitory activities in theophylline-stimulated murine B16 melanoma 4A5 cells of these isolates, including the new diterpenes (1–3, IC50 = 4.4, 8.6, and 4.6 μM, respectively), were found to be more than 6–87-fold higher than that of arbutin (174 μM), a commercially available positive control.

Diterpenoids from the aerial parts of Leonurus macranthus

Four new diterpenoids including one cis clerodane-type (1) and three highly oxygenated labdane-type diterpenes (2–4) were isolated from the aerial parts of Leonurus macranthus. Their structures were elucidated on the basis of spectroscopic data (NMR, UV, IR, and MS). Compound 1 represents the first example of cis clerodane-type diterpene in the plants of Leonurus genus. Compounds 1 and 4 exhibited weak inhibition of nitric oxide production in lipopolysaccharide-stimulated BV-2 microglial cells with IC50 values of 35.8±3.6μmol/L and 48.6±4.8μmol/L, respectively

Two new labdane diterpenoids from the foliar exudates of Blakiella bartsiifolia

Two new labdane-type diterpenes, blakielloside (1) and bartsiifolicoside (2), have been isolated from the dichloromethane extract of the foliar exudates of Blakiella bartsiifolia (S.F. Blake), an endemic and rare high altitude plant of the northern Andes, Venezuela. The structures of the new compounds were elucidated through extensive spectroscopic methods (IR, HR-FIA-MS, 1D and 2D NMR). Both natural products showed phytotoxic activity against Allium cepa, Cucumis sativus and Solanum lycopersicum.

Isolation, Characterization and Antiproliferative Activity of New Metabolites from the South African Endemic Red Algal Species Laurencia alfredensis.

The marine red algae of the genus Laurencia have been widely studied for their structurally diverse and biologically active secondary metabolites. We report here the natural product investigation of the organic extract of a newly identified South African endemic species, Laurencia alfredensis. A sequence of column chromatography, preparative TLC and normal phase HPLC resulted in the isolation of eleven compounds comprising three labdane-type diterpenes (1–3), four polyether triterpenes (4–7), three cholestane-type ecdysteroids (8–10) and a glycolipid (11). Compounds 1–3, 5–8 and 10 have not previously been reported, while compound 9 is reported here for the first time from a natural source and the known compound 11 isolated for the first time from the genus Laurencia. The structural elucidation and the relative configuration assignments of the compounds were accomplished by extensive use of 1D- and 2D-NMR, HR-ESI-MS, UV and IR spectroscopic techniques, while the absolute configuration of compound 1 was determined by single-crystal X-ray diffraction analysis. All compounds were evaluated against the MDA-MB-231 breast and HeLa cervical cancer cell lines. Compound 2 exhibited low micromolar antiproliferative activity (IC50 = 9.3 µM) against the triple negative breast carcinoma and compound 7 was similarly active (IC50 = 8.8 µM) against the cervical cancer cell line.

Comparison of essential oils from Cistus species growing in Sardinia

Cistus genus is present in Sardinia with large populations of C. monspeliensis, C. salvifolius, C. creticus subsp. eriocephalus and few stations of C. albidus, C. creticus subsp. creticus and C. creticus subsp. corsicus. No chemical studies are currently being carried on Cistus species of Sardinia. The essential oils have shown six different profiles. C. creticus subsp. eriocephalus showed a high amount of manoyl oxide and its isomer (70%). C. salvifolius has pointed out the group of labdans, (20%); another consistent percentage is made of perfumed molecules as ionone and its derivate. Several linear hydrocarbons were produced by C. monspeliensis, and the heneicosane was the most represented element. In C. albidus no labdane-type diterpenes were identified. Analysis of C. creticus subsp creticus revealed several oxygenated sesquiterpenes and labdane-type diterpenes, especially manoyl oxide. C. creticus subsp. corsicus was qualitatively very similar to C. creticus subsp. creticus, notably concerning the labdane-type compounds.

Trichome patterning control involves TTG1 interaction with SPL transcription factors.

Epidermal cell differentiation is a paramount and conserved process among plants. In Arabidopsis, a ternary complex formed by MYB, bHLH transcription factors and TTG1 modulates unicellular trichome morphogenesis. The formation of multicellular glandular trichomes of the xerophytic shrub Cistus creticus that accumulate labdane-type diterpenes, has attained much attention renowned for its medicinal properties. Here, we show that C. creticus TTG1 (CcTTG1) interacts with the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPLA/B) proteins, putative homologs of AtSPL4/5 that in turn interact with AtTTG1. These interactions occur between proteins from evolutionarily distant species supporting the conserved function of TTG1-SPL complex. Overexpression of AtSPL4 and AtSPL5 decreased the expression of GLABRA2 (AtGL2), the major regulator of trichome morphogenesis, resulting in trichome reduction on the adaxial surface of cauline leaves, thereby illuminating the significance of TTG1-SPLs interactions in trichome formation control. AtGL2 and AtSPL4 have opposite expression patterns during early stages of leaf development. We postulate an antagonistic effect between SPLs and the heterogeneous MYB-bHLH factors binding to TTG1. Hence, the SPLs potentially rearrange the complex, attenuating its transcriptional activity to control trichome distribution.