Biologically active alkylated coumarins from Kayea assamica

Antimalarial compounds from the climbing stems of salacia debilis

Salacia debilis Walp., (Celastraceae) is used traditionally in West Africa for the treatment of malaria. However, no scientific reports validating these effects and its active constituents are on record. Therefore, this study is aimed at evaluating the antimalarial effects, of its ethanolic extract and isolated compounds against Plasmodium falciparum 3D7 and P. berghei ANKA strains. Using chromatographic, spectrometric and spectroscopic techniques three compounds were isolated and characterised. The extract of S. debilis was active against P. falciparum 3D7, in an in vitro assay with IC50 of 12.0 ± 0.32 µg/ml. The three isolated compounds, namely 1,10-dihydroxy-6H-benzo[c]chromen-6-one (1), 8- hydroxy-3,4-dimethoxydibenzo[b,d]furan-1-carboxylic acid (2) and benzyl-2-methoxybenzoate (3), also showed antimalarial activity against Plasmodium berghei ANKA strain in curative and suppressive in vivo assays. The ethanolic extract and isolated compounds of S. debilis possess antimalarial effects. The isolated compounds may be responsible, at least in part, for the observed activities of the extract.

Crystal structure of 3-(3-bromophenyl)-1′,3′-dimethyl-2′H,3H,4H-spiro[furo[3, 2-c]chromene-2,5′-pyrimidine]-2′,4,4′,6′(1′H,3′H) tetraone, C22H15BrN2O6

C22H15BrN2O6, monoclinic, P21/c (No. 14), a = 5.1760 (5) Å, b = 17.5652(19) Å, c = 21.734(2) Å, β = 94.690(3) °, Z = 4, V = 1969.3(3) Å3, R gt (F) = 0.0569, wR ref (F 2) = 0.1206, T = 170 K.

Bioactive Compounds from Medicinal Plants in Myanmar

Myanmar is a country with rich natural resources and of these, medicinal plants play a vital role in the primary health care of its population. The people of Myanmar have used their own system of traditional medicine inclusive of the use of medicinal plants for 2000 years. However, systematic and scientific studies have only recently begun to be reported. Researchers from Japan, Germany, and Korea have collaborated with researchers in Myanmar on medicinal plants since 2000. During the past two decades, over 50 publications have been published in peer-reviewed journals. Altogether, 433 phytoconstituents, including 147 new and 286 known compounds from 26 plant species consisting of 29 samples native to Myanmar, have been collated. In this contribution, phytochemical and biological investigations of these plants, including information on traditional knowledge are compiled and discussed.

Non-nitrogenous Plant-derived Constituents with Antiplasmodial Activity

The paper is a compilation of the studies reported in the literature concerning non-nitrogenous natural constituents that have shown antiplasmodial activity and aims to provide a basis for further in vivo studies as well as for clinical trials to develop new antimalarial agents. Due to the increasingly unsatisfactory outcomes for N-heterocyclic drugs, coupled with the rising incidence of the deadly falciparum malaria, the advent of non-nitrogenous lead compounds is timely, signaling a new era of antimalarial chemotherapy. Currently a few non-nitrogenous molecules are used in therapy, but many promising molecules of plant origin are under study, such as peroxide sesquiterpenes, quinoid triterpenes, quassinoids, gallic acid derivatives, lignans, flavonoids and biflavonoids, xanthones, naphthoquinones and phenylanthraquinones. Many of these constituents are isolated from plants used traditionally to treat malaria and fever. Ethnopharmacology can still be considered as a rich source of lead molecules.

Design, Synthesis and Biological Evaluation of 1H-1,2,3-Triazole-Linked-1H-Dibenzo[b,h]xanthenes as Inductors of ROS-Mediated Apoptosis in the Breast Cancer Cell Line MCF-7

BACKGROUND

Low molecular weight 1,2,3-triazoles and naphthoquinones are endowed with various types of biological activity, such as against cancer, HIV and bacteria. However, in some cases, the conjugation of these two nuclei considerably increases their biological activities.

OBJECTIVE

In this work, we decided to study the synthesis and screening of bis-naphthoquinones and xanthenes tethered to 1,2,3-triazoles against cancer cell lines, specifically the human breast cancer cell line MCF-7.

RESULTS

Starting from lawsone and aryl-1H-1,2,3-triazole-4-carbaldehydes (10a-h) several new 7- (1-aryl-1H-1,2,3-triazol-4-yl)-6H-dibenzo[b,h]xanthene-5,6,8,13(7H)-tetraones (12a-h) and 3,3'- ((1-aryl-1H-1,2,3-triazol-4-yl)methylene)bis(2-hydroxynaphthalene-1,4-diones) 11a-h were synthesized and evaluated for their cytotoxic activities using the human breast cancer cell line MCF-7 and the non-tumor cell line MCF10A as control. We performed test of cell viability, cell proliferation, intracellular ATP content and cell cytometry to determine reactive oxygen species (ROS) formation.

CONCLUSIONS

Based on these results, we found that compound 12a promotes ROS production, interfering with energy metabolism, cell viability and proliferation, and thus promoting whole cell damage.

Potential cytotoxic and selective effect of new benzo[b]xanthenes against oral squamous cell carcinoma

Aim: The current work shows a new synthetic methodology to obtain 21 naphthoquinones that have been evaluated against oral cavity cancer. The compounds were obtained by a three-component reaction involving lawsone, dimedone and aromatic aldehydes catalyzed by lithium chloride under microwave irradiation to produce families of 1,4- and 1,2-naphthoquinones. Results: A clonogenic assay was performed on SCC9 cell line cultures with all compounds, revealing five very active compounds. In the 3,4,5-dimethylthiazol-2,5-diphenyltetrazolium bromide cell viability assay using three different cell lines (SCC9, SCC4 and SCC25), 8c had an average IC50 of approximately 1.45 μM capable of reducing tumor cell viability, approximately 90-times higher than carboplatin.Conclusion: Therefore, the xanthene-naphthoquinone derivatives show promising bioactivity for oral cavity cancer treatment.

Screening of some lesser known tree-borne oilseed plants from North-East India for their oil content and major fatty acid components

Forest of North-East India is rich in a variety of tree borne oilseeds and there were no serious efforts to exploit the less known oilseeds of the forest origin. Considering the vast plant wealth and with an objective to explore these untapped potentialities of oilseed resources of NE India, a research program was undertaken. The present communication is based on the investigation of seeds of 14 lesser known plant species for fats and oils. The screened plant species exhibited oil yield ranging from 4.71% to 48.43% on dry weight basis. Alseodaphne andersonii showed significant amount of tocols while Garcinia xanthochymus showed significant amount of phytosterol. Gas liquid chromatography analysis of methyl ester extracted fatty acid indicated dominant fraction of Oleic acid in 6 numbers of species, followed by Linoleic acid in 3 species, Lauric acid in 3 species, and Palmitic acid in 2 species. The majority of the species (9 species) showed higher amount of unsaturated fatty acid content in the oils which suggested that the species may serve as valuable raw materials for vegetable oil which can be explored as substitute for industrial feasibility while restshowed higher amount of saturated fatty acids which suggested that these species may serve as important industrial by-products.

The value of pyrans as anticancer scaffolds in medicinal chemistry

Pyran-based heterocycles are promising for anticancer drug discovery.

Extraction, characterization and biological studies of phytochemicals from Mammea suriga

The present work involves extraction of phytochemicals from the root bark of a well-known Indian traditional medicinal plant, viz. Mammea suriga, with various solvents and evaluation of their in vitro antimicrobial and antioxidant activities using standard methods. The phytochemical analysis indicates the presence of some interesting secondary metabolites like flavonoids, cardiac glycosides, alkaloids, saponins and tannins in the extracts. Also, the solvent extracts displayed promising antimicrobial activity against Staphylococcus aureus, Bacillus subtilis and Cryptococcus neoformans with inhibition zone in a range of 20-33 mm. Further, results of their antioxidant screening revealed that aqueous extract (with IC₅₀ values of 111.51±1.03 and 31.05±0.92 μg/mL in total reducing power assay and DPHH radical scavenging assay, respectively) and ethanolic extract (with IC₅₀ values of 128.00±1.01 and 33.25±0.89 μg/mL in total reducing power assay and DPHH radical scavenging assay, respectively) were better antioxidants than standard ascorbic acid. Interestingly, FT-IR analysis of each extract established the presence of various biologically active functional groups in it.

Lawsone in organic synthesis

Lawsone has been used as the starting material for the synthesis of a variety of biologically active compounds and materials.

Antiproliferative and apoptotic effects of compounds from the flower of Mammea siamensis (Miq.) T. Anders. on human cancer cell lines

On the search for anti-cancer compounds from Thai traditional herb medicines, a bioassay-guided fractionation and chemical investigation of the methanol extract of Mammea siamensis flower resulted in the isolation and identification of eight compounds (1-8) including a novel geranylated coumarin, namely mammeanoyl (2), and seven known compounds (1 and 3-8). The structure of new compound 2 was elucidated based on the extensive spectroscopic and chemical methods. Among the isolated compounds, three structurally related coumarins 3, 4, and 5 showed significant antiproliferative activities against human leukemia and stomach cancer cell lines. However, these compounds did not affect the cell viabilities of colon cancer, hepatoma, and normal skin fibroblast cell lines. Further analysis demonstrated that the morphological features of apoptosis including DNA fragmentation and chromatin condensation were observed in human leukemia HL-60 cells treated with compounds 3, 4, and 5. In addition, compound 3 led to caspase-3 activation and cleavage of poly (ADP-ribose) polymerase (PARP), and compound 3-induced DNA fragmentation was inhibited by caspase-specific inhibitors. These results suggest that compound 3, 4, and 5 exert antiproliferative actions through apoptotic cell death in leukemia cells and these compounds may have the potential to be developed into new anti-cancer drug candidates.

Disesquiterpene and sesquiterpene coumarins from Ferula pseudalliacea, and determination of their absolute configurations

The first disesquiterpene coumarin, sanandajin, five sesquiterpene coumarins, kamolonol acetate, fekrynol acetate, ethyl galbanate, methyl galbanate, farnesiferol B, and a sesquiterpene, aristolone, were isolated from a n-hexane extract of Ferula pseudalliacea roots. The structures were elucidated by 1D and 2D NMR, HR-ESIMS data, and kamolonol acetate was confirmed by single-crystal X-ray analysis. The absolute configuration of compounds was established by comparison of experimental and simulated ECD spectra using time dependence density function theory (TDDFT). In vitro antiplasmodial activity against Plasmodium falciparum K1 strain was determined. sanandajin, kamolonol acetate and methyl galbanate showed moderate antiplasmodial activity, with IC(50) values of 2.6, 16.1 and 7.1 μM, respectively.

Cytotoxic Coumarins from the Bark of Mammea siamensis

A new geranylated coumarin, (E)-4-(1-hydroxypropyl)-5,7-dihydroxy-6-(3,7-dimethyl-2,6-octadienyl)-8-(3-methyl-1-oxobutyl)coumarin (named surangin D), was isolated from the bark of Mammea siamensis collected in Vietnam, along with four known coumarins, surangins B and C, and theraphins B and C, and seven xanthones, 1,7-dihydroxyxanthone, 7-hydroxy-1-methoxyxanthone, 1,7-dimethoxyxanthone, 1,7-dimethoxy-6-hydroxyxanthone, 1,6,7-trihydroxyxanthone, 1,3,7-trihydroxyxanthone, and 1,7-dihydroxy-3-methoxyxanthone. Their structures were determined by spectroscopic methods (mainly 1D- and 2D-NMR) and preparation of methylated derivatives. The four coumarins, surangins C and D and theraphins B and C, were tested for inhibition of cell proliferation in DLD-1 (colon cancer), MCF-7 (breast adenocarcinoma), HeLa (human cervical cancer) and NCI-H460 (human lung cancer) cell lines using the sulforhodamine B (SRB) assay. In all four cell lines, theraphin C showed the strongest activity (IC₅₀ in the range of 1.6-5.7 µM). Testing the anti-proliferative effect of the methylated derivatives showed reduced cellular effects of all derivatives, indicating that the number and position of free hydroxyl groups were very important for the anti-proliferative effect.

Natural and semisynthetic mammea-type isoprenylated dihydroxycoumarins uncouple cellular respiration

In an effort to identify natural product-based molecular-targeted antitumor agents, mammea-type coumarins from the tropical/subtropical plant Mammea americana were found to inhibit the activation of HIF-1 (hypoxia-inducible factor-1) in human breast and prostate tumor cells. In addition to the recently reported mammea E/BB (15), bioassay-guided fractionation of the active extract yielded 14 mammea-type coumarins including three new compounds, mammea F/BB (1), mammea F/BA (2), and mammea C/AA (3). The absolute configuration of C-1' in 1 was determined by the modified Mosher's method on a methylated derivative. These coumarins were evaluated for their effects on mitochondrial respiration, HIF-1 signaling, and tumor cell proliferation/viability. Acetylation of 1 afforded a triacetoxylated product (A-2) that inhibited HIF-1 activation with increased potency in both T47D (IC(50) 0.83 μM for hypoxia-induced) and PC-3 cells (IC(50) 0.94 μM for hypoxia-induced). Coumarins possessing a 6-prenyl-8-(3-methyloxobutyl) substituent pattern exhibited enhanced HIF-1 inhibitory effects. The O-methylated derivatives were less active at inhibiting HIF-1 and suppressing cell proliferation/viability. Mechanistic studies indicate that these compounds act as anionic protonophores that potently uncouple mitochondrial electron transport and disrupt hypoxic signaling.

Mammea E/BB, an isoprenylated dihydroxycoumarin protonophore that potently uncouples mitochondrial electron transport, disrupts hypoxic signaling in tumor cells

The mammea-type coumarin mammea E/BB (1) was found to inhibit both hypoxia-induced and iron chelator-induced hypoxia-inducible factor-1 (HIF-1) activation in human breast tumor T47D cells with IC(50) values of 0.96 and 0.89 μM, respectively. Compound 1 suppressed the hypoxic induction of secreted VEGF protein (T47D cells) and inhibited cell viability/proliferation in four human tumor cell lines. Compound 1 (at 5 and 20 μM) inhibited human breast tumor MDA-MB-231 cell migration. While the mechanisms that underlie their biological activities have remained unknown, prenylated mammea coumarins have been shown to be cytotoxic to human tumor cells, suppress tumor growth in animal models, and display a wide variety of antimicrobial effects. Mechanistic studies revealed that 1 appears to exert an assemblage of cellular effects by functioning as an anionic protonophore that potently uncouples mitochondrial electron transport and disrupts mitochondrial signaling in human tumor cell lines.

Pyranocoumarins from the twigs of Mammea siamensis

Four unusual pyranocoumarins (1-4) have been isolated from the dried twigs of M. siamensis. The structures were determined by spectroscopic data, especially 1D and 2D NMR experiments.

Siamenols A-D, Four New Coumarins from Mammea siamensis

Further investigation of the dichloromethane extract of the twigs of Mammea siamensis led to the isolation of four novel coumarins, named siamenols A-D (1-4) together with three known xanthones. The structures of the new coumarins were elucidated by spectroscopic analysis, including 2D NMR spectroscopic data. In addition, the absolute stereochemistry of hydroxyl group of siamenol C (3) was determined to be S configuration by using modified Mosher's method.

Phloroglucinol derivatives from Mallotus pallidus

From the leaves of Mallotus pallidus were isolated five phloroglucinol derivatives, namely pallidusol, dehydropallidusol, pallidol, mallopallidol and homomallopallidol. Their structures were determined by means of spectroscopic methods of analysis.