Steryl epoxide, secobutanolide and butanolides from the stem wood of Machilus zuihoensis

γ-Lactones from Persea americana and Persea fulva - in Vitro and in Silico Evaluation of Trypanosoma cruzi Activity

In the present study, five known γ-lactones (majoranolide B - 1, majorenolide - 2, majorynolide - 3, lincomolide D - 4, and isolinderanolide E - 5), as well as a new one (perseanolide - 6), were isolated from Persea fulva and P. americana. All isolated compounds exhibited potential activity against trypomastigote forms of Trypanosoma cruzi, whereas compounds 2 (EC₅₀ of 4.8 μM) and 6 (EC₅₀ of 3.6 μM) displayed superior activity than the positive control benznidazole (EC₅₀ of 16.4 μM), with selectivity index (SI) values of 17.8 and >55.6, respectively (benznidazole, SI>12.2). Molecular docking studies were performed for 1-6 against six T. cruzi molecular targets. Using this approach, we observed that, even though perseanolide (6) showed favorable docking to several studied targets, the results were especially promising for hypoxanthine phosphoribosyl transferase (PDB 1TC1). As PDB 1TC1 is associated to the transference of a monophosphorylated ribose from phosphoribosylpyrophosphate (PRPP) in the ribonucleotide synthesis pathway, this interaction may affect the survival of T. cruzi in mammalian cells. The data herein also indicate that possible intermolecular interactions between 6 and PDB 1TC1 derive from (i) hydrogen bonds in the α,β-unsaturated-γ-lactone unity and (ii) hydrophobic interactions in the long-chain alkyl group. Based on our results, perseanolide (6), reported for the first time in this work, can auspiciously contribute to future works regarding new trypanocidal agents.

Phytochemical Investigation and Anti-Inflammatory Activity of the Leaves of Machilus japonica var. kusanoi

In a series of anti-inflammatory screenings of lauraceous plants, the methanolic extract of the leaves of Machilus japonica var. kusanoi (Hayata) J.C. Liao showed potent inhibition on both superoxide anion generation and elastase release in human neutrophils. Bioassay-guided fractionation of the leaves of M. japonica var. kusanoi led to the isolation of twenty compounds, including six new butanolides, machinolides A–F (1–6), and fourteen known compounds (7–20). Their structures were characterized by 1D and 2D NMR, UV, IR, CD, and MS data. The absolute configuration of the new compounds were unambiguously confirmed by single-crystal X-ray diffraction analyses (1, 2, and 3) and Mosher’s method (4, 5, and 6). In addition, lignans, (+)-eudesmin (11), (+)-methylpiperitol (12), (+)-pinoresinol (13), and (+)-galbelgin (16) exhibited inhibitory effects on N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-induced superoxide anion generation in human neutrophils with IC₅₀ values of 8.71 ± 0.74 μM, 2.23 ± 0.92 μM, 6.81 ± 1.07 μM, and 7.15 ± 2.26 μM, respectively. The results revealed the anti-inflammatory potentials of Formosan Machilus japonica var. kusanoi.

Advances in catalytic and protecting-group-free total synthesis of natural products: a recent update

Catalytic processes in protecting-group-free syntheses of natural products are fast emerging towards achieving the goal of efficiency and economy in total synthesis. Present day sustainable development in synthesis of natural products does not permit the luxury of using stoichiometric reagents and protecting groups. Catalysis and step-economy can contribute significantly toward economy and efficiency of synthesis. This feature article details the ingenious efforts by many researchers in the last couple of years toward concise total syntheses, based on catalytic steps and protecting-group-free-strategies. These would again serve as guidelines in future development of reagents and catalysts aimed at achieving higher efficiency and chemoselectivity to the point that catalysis and protecting-group-free synthesis will be an accepted common practice.

Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene

Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with lithiated epoxysilanes. Aliphatic and electron-rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron-deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the C-Si and C-B bond breaking transition states. This vinylidene homologation was used in a short six-step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.

Identification of α-Glucosidase Inhibitors in Machilus litseifolia by Combined Use of High-Resolution α-Glucosidase Inhibition Profiling and HPLC-PDA-HRMS-SPE-NMR

Type 2 diabetes is a chronic multifactorial disease affecting more than 425 million people worldwide, and new selective α-glucosidase inhibitors with fewer side effects are urgently needed. In this study, a crude ethyl acetate extract of Machilus litseifolia was fractionated by solid-phase extraction using C₁₈ cartridges to give a fraction enriched in α-glucosidase inhibitors. Subsequent microfractionation and bioassaying of the eluate by high-performance liquid chromatography (HPLC) using a complementary pentafluorophenyl column allowed construction of a high-resolution α-glucosidase inhibition profile (biochromatogram). This was used to target high-performance liquid chromatography-photodiode array detection-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-PDA-HRMS-SPE-NMR) analysis toward α-glucosidase inhibitors. This led to the identification of 13 dicoumaroylated flavonol rhamnosides, of which seven (8, 10, 12a, 12b, 16, 17, and 18) are reported for the first time, and two lignans, of which one (5) is reported for the first time. IC₅₀ values of isolated compounds toward α-glucosidase range from 5.9 to 35.3 μM, which is 8 to 91 times lower than the IC₅₀ value of 266 μM measured for the reference compound acarbose.

Biosynthetic investigation of γ-lactones in Sextonia rubra wood using in situ TOF-SIMS MS/MS imaging to localize and characterize biosynthetic intermediates

Molecular analysis by parallel tandem mass spectrometry (MS/MS) imaging contributes to the in situ characterization of biosynthetic intermediates which is crucial for deciphering the metabolic pathways in living organisms. We report the first use of TOF-SIMS MS/MS imaging for the cellular localization and characterization of biosynthetic intermediates of bioactive γ-lactones rubrynolide and rubrenolide in the Amazonian tree Sextonia rubra (Lauraceae). Five γ-lactones, including previously reported rubrynolide and rubrenolide, were isolated using a conventional approach and their structural characterization and localization at a lateral resolution of ~400 nm was later achieved using TOF-SIMS MS/MS imaging analysis. 2D/3D MS imaging at subcellular level reveals that putative biosynthetic γ-lactones intermediates are localized in the same cell types (ray parenchyma cells and oil cells) as rubrynolide and rubrenolide. Consequently, a revised metabolic pathway of rubrynolide was proposed, which involves the reaction between 2-hydroxysuccinic acid and 3-oxotetradecanoic acid, contrary to previous studies suggesting a single polyketide precursor. Our results provide insights into plant metabolite production in wood tissues and, overall, demonstrate that combining high spatial resolution TOF-SIMS imaging and MS/MS structural characterization offers new opportunities for studying molecular and cellular biochemistry in plants.

Inhibition of Collagen-Induced Platelet Aggregation by the Secobutanolide Secolincomolide A from Lindera obtusiloba Blume

Atherothrombosis is one of the main underlying cause of cardiovascular diseases. In addition to treating atherothrombosis with antithrombotic agents, there is growing interest in the role of natural food products and biologically active ingredients for the prevention and treatment of cardiovascular diseases. This study aimed to investigate the effect of secolincomolide A (3) isolated from Lindera obtusiloba Blume on platelet activity and identify possible signaling pathways. In our study, the antiplatelet activities of 3 were measured by collagen-induced platelet aggregation and serotonin secretion in freshly isolated rabbit platelets. Interestingly, 3 effectively inhibited the collagen-induced platelet aggregation and serotonin secretion via decreased production of diacylglycerol, arachidonic acid, and cyclooxygenase-mediated metabolites such as thromboxane B₂ (TXB₂), and prostaglandin D₂ (PGD₂). In accordance with the antiplatelet activities, 3 prolonged bleeding time and attenuated FeCl₃-induced thrombus formation in arterial thrombosis model. Notably, 3 abolished the phosphorylation of phospholipase Cγ2 (PLCγ2), spleen tyrosine kinase (Syk), p47, extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase B (Akt) by inhibiting the activation of the collagen receptor, glycoprotein VI (GPVI). Taken together, our results indicate the therapeutic potential of 3 in antiplatelet action through inhibition of the GPVI-mediated signaling pathway and the COX-1-mediated AA metabolic pathways.

Chemical constituents and bioactivity of Formosan lauraceous plants

Taiwan is rich in lauraceous plants. A review of 197 references based on the chemical analysis and bioactivity of indigenous lauraceous plants carried out by native scientists from 1963 to 2014 has been compiled. About 303 new compounds and thousands of known compounds comprising alkaloids and non-alkaloids with diverse structures have been isolated or identified from indigenous plants belonging to the 11 lauraceous genera. The volatile components, however, have been excluded from this review. This review provides an overview of the past efforts of Taiwan scientists working on secondary metabolites and their bioactivity in native lauraceous plants. The potential of lauraceous plants worthy of further study is also noted. The contents will be helpful for the chemotaxonomy of Lauraceae and be of value for the development of native Formosan lauraceous plants.

Antiproliferative Compounds from Ocotea macrocarpa from the Madagascar Dry Forest1

Bioassay-directed fractionation of an antiproliferative ethanol extract of the roots of Ocotea macrocarpa (Lauraceae) afforded the new butanolide macrocarpolide A (1), and the two new secobutanolides macrocarpolides B (2) and C (3), together with the known butanolides linderanolide B (4) and isolinderanolide (5). The structure elucidation of all compounds was carried out based on NMR and mass spectroscopic data analyses. The absolute configurations of all compounds isolated were determined by comparison of their optical rotation values with those found in literature. Compounds 1-5 showed good antiproliferative activities against the A2780 ovarian cell line, with IC₅₀ values of 2.57 ± 0.12 (1), 1.98 ± 0.23 (2), 1.67 ± 0.05 (3), 2.43 ± 0.41 (4), and 1.65 ± 0.44 µM (5), respectively.

Glycosides from the bark of Machilus robusta

Six new glycosidic constituents (1-6), together with 10 known analogs, have been isolated from the bark of Machilus robusta. Structures of the new compounds, including the absolute configurations, were determined by spectroscopic and chemical methods as ( - )-nectandrin B-β-d-glucopyranoside (1), ( - )-(7R,7'R,8S,8'R)-4,4'-dihydroxy-3,3'-dimethoxy-7,7'-epoxylignan-4-O-β-d-glucopyranoside (2), ( - )-(7R,7'R,8S,8'R)-4,4'-dihydroxy-3,3'-dimethoxy-7,7'-epoxylignan-4'-O-β-d-glucopyranoside (3), ( - )-(8S,8'R)-4,4'-dihydroxy-3,3',5'-trimethoxylignan-4'-O-β-d-glucopyranoside (4), ( - )-(7R,8R)-syringylglycerol-8-O-β-d-glucopyranoside (5), and ( - )-3-hydroxy-2-methyl-4-pyrone-3-O-β-d-xylopyranosyl-(1 → 6)-O-β-d-glucopyranoside (6), respectively.

Dammarane glycosides from the root of Machilus yaoshansis

Nine new dammarane triterpene glycosides (1-3 and 8-13) and 12 known analogues have been isolated from an ethanol extract of the roots of Machilus yaoshansis. Compounds 1-7 have an uncommon 20,23-dihydroxydammar-24-en-21-oic acid-21,23-lactone moiety that was previously reported in compounds isolated from Gynostemma pentaphyllum. The configurations of the lactone moieties in 1-3 were determined by comparison of the experimental ECD spectra of 1-3 and the hydrolysates, 1a and 1b, with the corresponding calculated ECD spectra. On the basis of NMR and ECD data analysis of 1-7, the previously reported C-20 and C-23 configurations of 4-7 and related derivatives from Gynostemma pentaphyllum were revised. In addition, the application of NMR data and Cotton effects to the determination of the relative and absolute configurations of the γ-lactone moiety in 3β,20,23-trihydroxydammar-24-en-21-oic acid-21,23-lactone derivatives is discussed.

Butanolide derivatives from the bark of Machilus yaoshansis

Six new butanolide derivatives with long aliphatic side chains (1-6), together with 23 known lipophilic constituents, were isolated from the bark of Machilus yaoshansis. Their structures were elucidated by spectroscopic and chemical methods. All the isolates were evaluated for cytotoxic and anti-inflammatory activities.

Cucurbitane glucosides from the root of Machilus yaoshansis

Seven new cucurbitane triterpene glucosides (1-5, 8, and 9) and five known analogues (6, 7, 10, cucurbitacin I 2-O-β-d-glucopyranoside, and khekadaengoside K) have been isolated from an ethanol extract of roots of Machilus yaoshansis. Compounds 1 and 2 have an unusual 16,23:22,25-diepoxy unit, 4 is an uncommon cucurbitane 25-carbamate with the carbamoyl amino group attached at C-24 to form an oxazolidinone ring in the side chain, and 8 is the first example of a trinorcucurbitane derivative. The configurations in several pairs of C-24 epimeric cucurbitacins with 24,25-dihydroxy-22-one side chains were assigned, and the validity of J(23a,24) and J(23b,24) values to differentiate the configuration at C-24 in these cucurbitane derivatives is discussed. Compounds 2-4 showed in vitro activity against protein tyrosine phosphatase 1B with IC50 values of 8.63, 2.81, and 4.26 μM, respectively. Cucurbitacin E 2-O-β-d-glucopyranoside (10) showed selective cytotoxicity against BGC-823 and A549 cancer cells with IC50 values of 4.98 and 3.20 μM, respectively.

Anti-inflammatory and free radial scavenging activities of the constituents isolated from Machilus zuihoensis

A new biflavonol glycoside, quercetin-3-O-β-D-glucopyranoside-(3'→O-3''')-quercetin-3-O-β-D-galactopyranoside (9), together with eight known compounds was isolated for the first time from the leaves of Machilus zuihoensis Hayata (Lauraceae). The structure of compound 9 was elucidated by various types of spectroscopic data analysis. Analysis of the biological activity assay found that compound 9 showed significant superoxide anion scavenging activity (IC₅₀ is 30.4 μM) and markedly suppressed LPS-induced high mobility group box 1 (HMGB-1) protein secretion in RAW264.7 cells. In addition, the HMGB-1 protein secretion was also inhibited by quercitrin (3), ethyl caffeate (6), and ethyl 3-O-caffeoylquinate (7) treatment. In the LPS-stimulated inducible nitric oxide synthase (iNOS) activation analysis, two known compounds, quercetin (1) and ethyl caffeate (6), were found to markedly suppress nitric oxide (NO) production (IC₅₀ value, 27.6 and 42.9 μM, respectively) in RAW264.7 cells. Additionally, it was determined that ethyl caffeate (6) down-regulated mRNA expressions of iNOS, IL-1β, and IL-10 in the LPS-treatment of RAW264.7 cells via a suppressed NF-kB pathway. These results suggested for the first time that the new compound 9 and other constituents isolated from M. zuihoensis have potential anti-inflammatory and superoxide anion scavenging effects. These constituents may be useful for treating various inflammatory diseases.

A new butanolide and a new secobutanolide from Litsea lii var. nunkao-tahangensis

The chloroform-soluble portion of the leaf extract of Litsea lii var. nunkao-tahangensis was further studied and these studies led to the isolation of a new butanolide, litsealiicolide C (1), and a new secobutanolide, secoisolitsealiicolide B (2), along with seven known compounds, linderanolide B (3), isolinderanolide C (4), secolincomolide A (5), secokotomolide A (6), (+)-beta-eudesmol (7), trans-phytol (8), and (-)-matairesinol (9). Their structures were established on the basis of spectral analysis and comparison with the literature data. In addition, the cytotoxicities against MCF-7, NCI-H460, and SF-268 cancer cell lines were measured in vitro and the results demonstrated that these metabolites have no cytotoxicity against the selected tumour cells.

Cytotoxic compounds from the stems of Cinnamomum tenuifolium

Three new butanolides, tenuifolide A (1), isotenuifolide A (2), and tenuifolide B (3), a new secobutanolide, secotenuifolide A (4), and one new sesquiterpenoid, tenuifolin (5), along with 16 known compounds were isolated from the stems of Cinnamomum tenuifolium. Their structures were determined by spectroscopic analyses. Compound 4 was found to induce apoptotic-related DNA damage, increase sub-G1 cells, and inhibit the growth of human prostate cancer cells, DU145. In addition, treatment with 4 significantly increased intracellular H2O2 and/or peroxide. The results show that 4 induced (a) noticeable reduction of mitochondrial transmembrane potential (DeltaPsim); (b) significant increase in the ratio of cytochrome c concentration (cytosol/mitochondria); and (c) subsequent activation of caspase-9/caspase-3. Antiproliferation caused by 4 was found to markedly decrease when pretreated with caspase-9/caspase-3 inhibitor. In ROS scavenging, antioxidant, NADPH oxidase, and NO inhibitor studies, pretreatment of DU145 cells with either DPI, dexamethasone, L-NAME, or mannitol decreased 4-induced intracellular DCF fluorescence of ROS. These results suggest that an increase of H2O2 and/or peroxide by 4 is the initial apoptotic event and 4 has anticancer effects on DU145 cells.

Cytotoxic constituents of the stems of Cinnamomum subavenium

The aim of this study was to evaluate the cytotoxic effects of three new butanolides, subamolides A - C (1-3), and a new secobutanolide, secosubamolide (4), on the human colorectal cancer cell line SW480. Compounds 1-4 are new and were isolated from the stems of Cinnamomum subavenium, along with 17 known compounds. The structures of 1-4 were determined by spectroscopic analysis. Propidium iodide staining and flow cytometry were used to evaluate DNA damage of the treated SW480 cells, and it was found that 1-4 caused DNA damage in a dose-dependent manner after 24 h of treatment.

Chemical and cytotoxic constituents from the leaves of Cinnamomum kotoense

Three new butanolides, kotomolide A (1), isokotomolide A (2), and kotomolide B (3), and a new secobutanolide, secokotomolide A (4), along with 21 known compounds were isolated from the leaves of Cinnamomum kotoense. Their structures were determined by spectroscopic analyses. Compound 4 was found to induce significant cell death in the human HeLa cell line. Apoptotic-related DNA damage can be positively related to the dose of compound 4. The DNA damage was measured by the percentage of subG1 (24 h after the treatment of compound 4) as determined by cell cycle analysis and TUNEL assay. Treatment with 4 significantly increased intracellular H2O2 and/or peroxide, nitric oxide (NO) at 1, 3, and 24 h. Our results also showed that compound 4 induced (a) noticeable reduction of mitochondrial transmembrane potential (DeltaPsi(m)), (b) activation of caspase 3/7, and (c) up-regulation of the p53 expression. Compound 4-induced DNA damage was found to markedly decrease when the cells were pretreated with an intracellular glutathione supplement (glutathione ethyl ester). These results suggest that an increase of H2O2 and/or peroxide by compound 4 is the initial apoptotic event. The intracellular GSH depletion is a critical event in compound 4-induced apoptosis in HeLa cells.