iridoids and plumericin

The vibrational circular dichroism (VCD) spectra of the two enantiomers of a chiral molecule are of equal magnitude and opposite sign: i.e. mirror-image enantiomers give mirror-image VCD spectra. In principle, the absolute configuration (AC) of a chiral molecule can therefore be determined from its VCD spectrum. In practice, the determination of the AC of a chiral molecule from its experimental VCD spectrum requires a methodology which reliably predicts the VCD spectra of its enantiomers. The only reliable methodology developed to date uses the Stephens quantum-mechanical theory of the rotational strengths of fundamental vibrational transitions, developed in the early 1980s, implemented using ab initio density functional theory in the GAUSSIAN program in the mid 1990s. This methodology has by now been widely used in determining ACs from experimental VCD spectra. In this article we discuss the protocol for determining the ACs of chiral molecules with optimum reliability and its implementation for a variety of molecules, including the D3 symmetry perhydrotriphenylene, a thiazino-oxadiazolone recently shown to be a highly active calcium entry channel blocker, the alkaloid natural products schizozygine, iso-schizogaline, and iso-schizogamine, and the iridoid natural products plumericin, iso-plumericin, and prismatomerin. The power of VCD spectroscopy in determining ACs, even for large organic molecules and for substantially conformationally-flexible organic molecules is clearly documented.

Topics: Alkaloids; Calcium Channel Blockers; Chrysenes; Circular Dichroism; Indenes; Indole Alkaloids; Indoles; Iridoids; Models, Chemical; Molecular Conformation; Optical Rotation; Quantum Theory; Spectrophotometry, Infrared; Stereoisomerism

Inflammatory bowel diseases (IBDs) are characterized by an inflammatory and oxidative stress condition in the intestinal tissue. In this study, we evaluated the effect of plumericin, one of the main bioactive components of Himatanthus sucuuba (Woodson) bark, on intestinal inflammation and oxidative stress, both in vitro and in vivo. The effect of plumericin (0.5-2 µM) in vitro was evaluated in rat intestinal epithelial cells (IEC-6) treated with lipopolysaccharides from E. coli (10 μg/mL) plus interferon-γ (10 U/mL). Moreover, a 2,4,6-dinitrobenzene sulfonic acid (DNBS)-induced colitis model was used to evaluate the anti-inflammatory and antioxidant activity of plumericin (3 mg/kg) in vivo. The results showed that plumericin significantly reduces intestinal inflammatory factors such as tumor necrosis factor-α, cyclooxygenase-2 and inducible nitric oxide synthase expression, and nitrotyrosine formation. Plumericin also inhibited nuclear factor-κB translocation, reactive oxygen species (ROS) release, and inflammasome activation. Moreover, plumericin activated the nuclear factor erythroid-derived 2 pathway in IEC-6. Using the DNBS-induced colitis model, a significant reduction in the weight loss and in the development of the macroscopic and histologic signs of colon injury, together with a reduced inflammatory and oxidative stress state, were observed in plumericin-treated mice. These results indicate that plumericin exerts a strong anti-inflammatory and antioxidant activity. Thus, it might be a candidate for the development of a new pharmacologic approach for IBDs treatment.

Topics: Animals; Anti-Inflammatory Agents; Cell Line; Colitis; Colon; Cyclooxygenase 2; Indenes; Inflammation; Inflammatory Bowel Diseases; Intestinal Mucosa; Iridoids; Male; Mice; NF-kappa B; Nitric Oxide Synthase Type II; Oxidative Stress; Rats; Reactive Oxygen Species; Tumor Necrosis Factor-alpha

The etiology of atherosclerosis and restenosis involves aberrant inflammation and proliferation, rendering compounds with both anti-inflammatory and anti-mitogenic properties as promising candidates for combatting vascular diseases. A recent study identified the iridoid plumericin as a new scaffold inhibitor of the pro-inflammatory NF-κB pathway in endothelial cells. We here examined the impact of plumericin on the proliferation of primary vascular smooth muscle cells (VSMC). Plumericin inhibited serum-stimulated proliferation of rat VSMC. It arrested VSMC in the G1/G0-phase of the cell cycle accompanied by abrogated cyclin D1 expression and hindered Ser 807/811-phosphorylation of retinoblastoma protein. Transient depletion of glutathione by the electrophilic plumericin led to S-glutathionylation as well as hampered Tyr705-phosphorylation and activation of the transcription factor signal transducer and activator of transcription 3 (Stat3). Exogenous addition of glutathione markedly prevented this inhibitory effect of plumericin on Stat3. It also overcame downregulation of cyclin D1 expression and the reduction of biomass increase upon serum exposure. This study revealed an anti-proliferative property of plumericin towards VSMC which depends on plumericin's thiol reactivity and S-glutathionylation of Stat3. Hence, plumericin, by targeting at least two culprits of vascular dysfunction -inflammation and smooth muscle cell proliferation -might become a promising electrophilic lead compound for vascular disease therapy.

Topics: Animals; Apocynaceae; Cells, Cultured; Cyclin D1; G1 Phase; Glutathione; Indenes; Iridoids; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Protein Processing, Post-Translational; Rats; Resting Phase, Cell Cycle; Signal Transduction; STAT3 Transcription Factor

The transcription factor NF-κB orchestrates many pro-inflammatory signals and its inhibition is considered a promising strategy to combat inflammation. Here we report the characterization of the natural product plumericin as a highly potent inhibitor of the NF-κB pathway with a novel chemical scaffold, which was isolated via a bioactivity-guided approach, from extracts of Himatanthus sucuuba, an Amazonian plant traditionally used to treat inflammation-related disorders.. A NF-κB luciferase reporter gene assay was used to identify NF-κB pathway inhibitors from H. sucuuba extracts. Monitoring of TNF-α-induced expression of the adhesion molecules VCAM-1, ICAM-1 and E-selectin by flow cytometry was used to confirm NF-κB inhibition in endothelial cells, and thioglycollate-induced peritonitis in mice to confirm effects in vivo. Western blotting and transfection experiments were used to investigate the mechanism of action of plumericin.. Plumericin inhibited NF-κB-mediated transactivation of a luciferase reporter gene (IC50 1 μM), abolished TNF-α-induced expression of the adhesion molecules VCAM-1, ICAM-1 and E-selectin in endothelial cells and suppressed thioglycollate-induced peritonitis in mice. Plumericin exerted its NF-κB pathway inhibitory effect by blocking IκB phosphorylation and degradation. Plumericin also inhibited NF-κB activation induced by transfection with the constitutively active catalytic subunit of the IκB kinase (IKK-β), suggesting IKK involvement in the inhibitory action of this natural product.. Plumericin is a potent inhibitor of NF-κB pathways with a new chemical scaffold. It could be further explored as a novel anti-inflammatory lead compound.

Topics: Animals; Anti-Inflammatory Agents; Apocynaceae; Cell Adhesion Molecules; Disease Models, Animal; Dose-Response Relationship, Drug; HEK293 Cells; Human Umbilical Vein Endothelial Cells; Humans; I-kappa B Kinase; I-kappa B Proteins; Indenes; Inflammation; Inflammation Mediators; Iridoids; Male; Mice; Mice, Inbred C57BL; NF-kappa B; Phosphorylation; Plant Extracts; Signal Transduction; Thioglycolates; Transfection

Because of the developing resistance of Mycobacterium species against currently available anti-mycobacterial drugs, there is an urgent need for new drug development. In this study, we have evaluated the in vitro anti-mycobacterial activity of Plumeria bicolor extract and its phytoconstituents - plumericin and isoplumericin against multi-drug resistance Mycobacterium tuberculosis.. The in vitro anti-mycobacterial activity of chloroform extract of P. bicolor, plumericin and isoplumericin were tested against M. tuberculosis (H37Rv) and four multi-drug resistant (MDR) clinical isolates by measuring the minimum inhibitory concentration (MIC) using MTT (Tetrazolium bromide [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide]) assay. The extract and both compounds were further evaluated by standard assay procedures to determine their minimum bactericidal concentration (MBC). Cytotoxicity of these compounds was performed against J774G8 murine macrophage cell lines. The activity was represented in the mean (±SD) of duplicate samples from three independent assays.. Plumericin showed better activity against pan sensitive as well as four MDR strains of M. tuberculosis with MIC values of 2.1 ± 0.12, 1.3 ± 0.15, 2.0 ± 0.07, 1.5 ± 0.13 & 2.0 ± 0.14 μg/mL and MBC values of 3.6 ± 0.22, 2.5 ± 0.18, 3.8 ± 0.27, 2.9 ± 0.20 & 3.7 ± 0.32 μg/mL than isoplumericin, respectively. Interestingly, both isolated active compounds showed an advantage over rifampicin (80 times) and isoniazid (8 times) by being highly active against the MDR strains. The extract and both compounds were found to be non-toxic against J774G8 macrophages up to the used concentrations.. Plumericin showed more potent activity than isoplumericin. The excellent activity of these compounds against MDR strains opens a possibility of obtaining new anti-mycobacterial drug candidate in near future.

Topics: Animals; Antitubercular Agents; Apocynaceae; Cell Line; Dose-Response Relationship, Drug; Humans; Indenes; Iridoids; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Plant Extracts; Tuberculosis, Multidrug-Resistant

The severe toxicity, exorbitant cost and emerging resistance of Leishmania species against most of the currently used drugs underscores the urgent need for the alternative drugs. The present study evaluates in vitro anti-leishmanial activity of Plumeria bicolor and its isolated compounds.. The in vitro anti-parasitic activity of chloroform extract of Plumeria bicolor, plumericin and isoplumericin were tested alongwith appropriate controls against promastigote and amastigote forms of Leishmania donovani using 96 well microtiter plate. The concentration used for assessing the anti-leishmanial activity of extract of Plumeria bicolor and both isolated compounds were 100 μg/ml and 15 μM, respectively. The viability of the cells was assessed by MTT assay. The cytotoxicity of these compounds was performed against J774G8 murine macrophage cells lines at the concentration of 30 μM.. The Plumeria bicolor extract showed activity with the IC 50 of 21±2.2 and 14±1.6 μg/ml against promastigote and amastigote forms of L. donovani, respectively. Plumericin consistently showed high activity with the IC 50 of 3.17±0.12 and 1.41±0.03 μM whereas isoplumericin showed the IC50 of 7.2±0.08 μM and 4.1±0.02 μM against promastigote and amastigote forms, respectively. Cytotoxic effect of the chloroform extract of P. bicolor, plumericin and isoplumericin was evaluated in murine macrophage (J774G8) model with CC50 value of 75±5.3 μg/ml, 20.6±0.5 and 24±0.7 μM, respectively.. Our results indicated that plumericin showed more potent activity than isoplumericin and might be a promising anti-leishmanial agent against L. donovani.

Topics: Animals; Antiparasitic Agents; Apocynaceae; Cell Line; Humans; Indenes; Inhibitory Concentration 50; Iridoids; Leishmania; Leishmania donovani; Macrophages; Mice; Plant Extracts

This study evaluated the in vitro antifungal activity of the chloroform extract of Plumeria bicolor and its phytoconstituents plumericin and isoplumericin against Candida species and Cryptococcus neoformans by measuring the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC). Plumericin's consistently high activity against Candida albicans, C. krusei, C. glabrata, C. tropicalis and Cryptococcus neoformans was more potent than isoplumericin and the standard antifungal drug nystatin suggesting its potential as a drug candidate for candidiasis and cryptococcosis.

Topics: Antifungal Agents; Apocynaceae; Candida; Cryptococcus neoformans; Indenes; Iridoids; Microbial Sensitivity Tests; Plant Extracts

The absolute configurations (ACs) of the iridoid natural products, plumericin (1) and isoplumericin (2), have been re-investigated using vibrational circular dichroism (VCD) spectroscopy, electronic circular dichroism (ECD) spectroscopy, and optical rotatory dispersion (ORD). Comparison of DFT calculations of the VCD spectra of 1 and 2 to the experimental VCD spectra of the natural products, (+)-1 and (+)-2, leads unambiguously to the AC (1R,5S,8S,9S,10S)-(+) for both 1 and 2. In contrast, comparison of time-dependent DFT (TDDFT) calculations of the ECD spectra of 1 and 2 to the experimental spectra of (+)-1 and (+)-2 does not permit definitive assignment of their ACs. On the other hand, TDDFT calculations of the ORD of (1R,5S,8S,9S,10S)-1 and -2 over the range of 365-589 nm are in excellent agreement with the experimental data of (+)-1 and (+)-2, confirming the ACs derived from the VCD spectra. Thus, the ACs initially proposed by Albers-Schönberg and Schmid are shown to be correct, and the opposite ACs recently derived from the ECD spectra of 1 and 2 by Elsässer et al. are shown to be incorrect. As a result, the ACs of other iridoid natural products obtained by chemical correlation with 1 and 2 are not in need of revision.

Topics: Circular Dichroism; Indenes; Iridoids; Models, Chemical; Models, Molecular; Molecular Conformation; Molecular Structure; Optical Rotation; Optical Rotatory Dispersion; Spectrophotometry, Infrared; Vibration

Extracts of seven medicinal plants used specifically against cutaneous leishmaniasis in the Madre de Dios region of Peru were evaluated in vitro against promastigote and axenic amastigote forms of Leishmania amazonensis. One of them showed interesting leishmanicidal activities (IC(50)=5 microg/ml in amastigotes). Bio-guided isolation of the stem bark's ethanol extract of Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson (Apocynaceae) afforded the spirolactone iridoids isoplumericin and plumericin. The latter showed a reduction of macrophage infection similar to that of the reference drug Amphotericin B (IC(50)=0.9 and 1 microM, respectively). These findings validate the traditional use of Himatanthus sucuuba in the treatment of cutaneous leishmaniasis (Uta) in Peru.

Topics: Animals; Antiprotozoal Agents; Apocynaceae; BALB 3T3 Cells; Biological Assay; Chlorocebus aethiops; Crystallography, X-Ray; Ethnobotany; Humans; In Vitro Techniques; Indenes; Indians, South American; Iridoids; Leishmania mexicana; Macrophages; Magnetic Resonance Spectroscopy; Male; Medicine, Traditional; Mice; Mice, Inbred BALB C; Peru; Plant Extracts; Spironolactone; Vero Cells

The absolute configurations of plumericin (1) and isoplumericin (2), isolated from Plumeria rubra, were re-assigned based on a combination of X-ray crystal-structure determination and quantum-mechanical calculations of their circular dichroism (CD) spectra. The experimental CD spectra showed an excellent match with those calculated for the (1S,5R,8R,9R,10R) absolute configuration (corresponding to ent-1 and ent-2, resp.), opposite to that generally accepted and published in the literature. Since the (false) plumericin configuration has been often used to derive the absolute configuration of related iridoids by chemical correlation, their absolute configurations also have to be reconsidered.

Topics: Apocynaceae; Indenes; Iridoids; Models, Molecular; Molecular Structure

Himatanthus sucuuba is an Amazonian tree with abundant, yet conflicting ethnobotanical information. Investigation of the polar and non-polar constituents led to the isolation of plumericin, a bioactive spirolactone iridoid, and four known pentacylic triterpenes: lupeol acetate, lupeol cinnamate, lupeol beta-phenyl propionate, and alpha-amyrin cinnamate.

Topics: 3T3 Cells; Animals; Antifungal Agents; Antineoplastic Agents, Phytogenic; Apocynaceae; HT29 Cells; Humans; Indenes; Iridoids; Mice; Mice, Inbred BALB C; Plant Bark; Plant Extracts; Spironolactone; Triterpenes; Tumor Cells, Cultured

The compounds 1-6 were isolated from the heartwood of Plumeria rubra, following bioactivity-directed fractionation. Plumericin 1 and isoplumericin 2 displayed molluscicidal, cytotoxic and antibacterial activity, 4-hydroxyacetophenone 3 was weakly cytotoxic, whereas the remaining glycosidic isolates (plumieride, 4; 13-O-coumaroylplumieride, 5; protoplumericine A, 6) were inactive in all test systems.

Topics: Animals; Antineoplastic Agents, Phytogenic; Cell Line; Indenes; Iridoids; Leukemia P388; Medicine, Traditional; Microbial Sensitivity Tests; Structure-Activity Relationship; Thailand

Topics: Anti-Bacterial Agents; Anti-Infective Agents; Antibiotics, Antitubercular; Apocynaceae; Humans; Indenes; Iridoids