Bioassay guided purification of cytotoxic natural products from a red alga Dichotomaria obtusata

Different solvent extracts of Dichotomaria obtusata (J. Ellis & Solander) Lamark, Galaxauraceae, a red algae collected from the coast of Bushehr in the Persain Gulf, was investigated for its cytotoxic properties and chemical constituents. The fresh alga, after extraction with methanol and dichloromethane were combined and partitioned between water, dichloromethane and ethyl acetate. The above fractions were then tested against MOLT-4 (human lymphoblastic leukemia) cancer cell line. The IC50 values of the dichloromethane and ethyl acetate layers of the crude extract were 29.8 ± 3.1 and 30.6 ± 7.9 μg/ml against MOLT-4 cells, respectively, while the water layer showed a week activity with IC50 > 50 μg/ml. After fractionation of the active extracts using open column chromatography over silica gel and preparative thin layer chromatography purification, two terpenoid derived compounds, trans-phytol palmitate and γ-tocopherol were isolated from the dichloromethane and ethyl acetate extracts. The structures of the compounds were elucidated using different spectral data including 1H NMR, 13C NMR, HSQC, HMBC and EI-MS. The IC50 values of compounds trans-phytol palmitate, γ-tocopherol and an undetermined mixture of compounds (F-13-14) were determined as 43.4 ± 1.6, – and 20.3 ± 6.2 μg/ml against LS180 (human colon adenocarcinoma); 53.2 ± 9.3, >100 and 27.6 ± 6.9 μg/ml against MCF-7 (human breast adenocarcinoma) and 40.0 ± 4.1, 48.8 ± 1.8 and 15.9 ± 0.3 μg/ml against MOLT-4 cell lines, respectively, which were comparable to the IC50 values of standard anticancer agent, cisplatin against the same cell lines. The red algae collected from the Persian Gulf contained substances that could inhibit the growth of human cancer cell lines and may represent a natural source for the discovery of novel anticancer agents. Keywords: Dichotomaria obtusata, Red algae, Trans-phytol palmitate, Tocopherol, Cytotoxic activit

Identification, quantification, spatiotemporal distribution and genetic variation of major latex secondary metabolites in the common dandelion (Taraxacum officinale agg.)

The secondary metabolites in the roots, leaves and flowers of the common dandelion (Taraxacum officinale agg.) have been studied in detail. However, little is known about the specific constituents of the plant’s highly specialized laticifer cells. Using a combination of liquid and gas chromatography, mass spectrometry and nuclear magnetic resonance spectrometry, we identified and quantified the major secondary metabolites in the latex of different organs across different growth stages in three genotypes, and tested the activity of the metabolites against the generalist root herbivore Diabrotica balteata. We found that common dandelion latex is dominated by three classes of secondary metabolites: phenolic inositol esters (PIEs), triterpene acetates (TritAc) and the sesquiterpene lactone taraxinic acid β-d-glucopyranosyl ester (TA-G). Purification and absolute quantification revealed concentrations in the upper mg g−1 range for all compound classes with up to 6% PIEs, 5% TritAc and 7% TA-G per gram latex fresh weight. Contrary to typical secondary metabolite patterns, concentrations of all three classes increased with plant age. The highest concentrations were measured in the main root. PIE profiles differed both quantitatively and qualitatively between plant genotypes, whereas TritAc and TA-G differed only quantitatively. Metabolite concentrations were positively correlated within and between the different compound classes, indicating tight biosynthetic co-regulation. Latex metabolite extracts strongly repelled D. balteata larvae, suggesting that the latex constituents are biologically active

The roots of <i>Salvia rhytidea:</i> a rich source of biologically active diterpenoids

<p>Sahandinone (<b>1</b>), 12-deoxysalvipisone (<b>2</b>), miltirone (<b>3</b>), 7α-acetoxyroyleanone (<b>4</b>), and labda-7,14-dien-13-ol (<b>5</b>) were isolated from the roots of <i>Salvia rhytidea</i> Benth. (Lamiaceae). Their structures were elucidated by a combination of spectroscopic analyses including EIMS and NMR. The ¹³C NMR spectroscopic data were revised for the quaternary carbons of both <b>1</b> and <b>3</b> with the help of HMBC spectra in respect to the spectral data previously reported in the literature. Compounds <b>1</b> and <b>3</b>, two very potent anticancer agents, were isolated in high yields from the roots of the plant. The biological activities of the plants’ constituents were reported in the literature as antimicrobial, cytotoxic and antimalarial are discussed in this article.</p> <p>The major anticancer agents from <i>Salvia rhytidea</i>.</p

Biosynthesis of 8-O-methylated benzoxazinoid defense compounds in maize

Benzoxazinoids are important defense compounds in grasses. Here, we investigated the biosynthesis and biological roles of the 8-O-methylated benzoxazinoids, DIM2BOA-Glc and HDM2BOA-Glc. Using quantitative trait locus mapping and heterologous expression, we identified a 2-oxoglutarate-dependent dioxygenase (BX13) that catalyzes the conversion of DIMBOA-Glc into a new benzoxazinoid intermediate (TRIMBOA-Glc) by an uncommon reaction involving a hydroxylation and a likely ortho-rearrangement of a methoxy group. TRIMBOA-Glc is then converted to DIM2BOA-Glc by a previously described O-methyltransferase BX7. Furthermore, we identified an O-methyltransferase (BX14) that converts DIM2BOA-Glc to HDM2BOA-Glc. The role of these enzymes in vivo was demonstrated by characterizing recombinant inbred lines, including Oh43, which has a point mutation in the start codon of Bx13 and lacks both DIM2BOA-Glc and HDM2BOA-Glc, and Il14H, which has an inactive Bx14 allele and lacks HDM2BOA-Glc in leaves. Experiments with near-isogenic maize lines derived from crosses between B73 and Oh43 revealed that the absence of DIM2BOA-Glc and HDM2BOA-Glc does not alter the constitutive accumulation or deglucosylation of other benzoxazinoids. The growth of various chewing herbivores was not significantly affected by the absence of BX13-dependent metabolites, while aphid performance increased, suggesting that DIM2BOA-Glc and/or HDM2BOA-Glc provide specific protection against phloem feeding insects