Novel cytotoxic brominated diterpenes from the red alga Laurencia obtusa

Five new brominated diterpenes, along with two known, have been isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Preveza in the Ionean Sea, Greece. The novel metabolites prevezols B-E possess two new carbon skeletons, to the best of our knowledge, unprecedented in the literature. The structures and the relative stereochemistry of the new natural products were established by means of spectral data analyses. The new metabolites were tested for their cytotoxic activity against five human cell lines. Two metabolites have exhibited significant cytotoxicity.     

New C15 Acetogenins from Two Species of Laurencia from the Aegean Sea

The chemical diversity of the approximately 1,200 natural products isolated from red algae of the genus Laurencia, in combination with the wide range of their biological activities, have placed species of Laurencia in the spotlight of marine chemists’ attention for over 60 years. The chemical investigation of the organic (CH₂Cl₂/MeOH) extracts of Laurencia microcladia and Laurencia obtusa, both collected off the coasts of Tinos island in the Aegean Sea, resulted in the isolation of 32 secondary metabolites, including 23 C₁₅ acetogenins (1–23), 7 sesquiterpenes (24–30) and 2 diterpenes (31 and 32). Among them, six new C₁₅ acetogenins, namely 10-acetyl-sagonenyne (2), cis-sagonenyne (3), trans-thuwalenyne C (4), tinosallene A (11), tinosallene B (12) and obtusallene XI (17), were identified and their structures were elucidated by extensive analysis of their spectroscopic data. Compounds 1–3, 5–11, 13 and 15–32 were evaluated for their antibacterial activity against Staphylococcus aureus and Escherichia coli.     

Rank estimation in reduced-rank regression

Reduced rank regression assumes that the coefficient matrix in a multivariate regression model is not of full rank. The unknown rank is traditionally estimated under the assumption of normal responses. We derive an asymptotic test for the rank that only requires the response vector have finite second moments. The test is extended to the nonconstant covariance case. Linear combinations of the components of the predictor vector that are estimated to be significant for modelling the responses are obtained.     

Novel peripherally functionalized seco-porphyrazines: synthesis, characterization and spectroscopic evaluation

Co-macrocyclizations of 2,3-dipropylmaleonitrile and 2,3-di-(4-(methoxycarbonyl)phenyl)maleonitrile, respectively, with N,N′-dibenzyl-N,N′-di-(11-tetrahydropyranyloxy-3,6,9-trioxo-undecyl))maleonitrile and N,N,N′,N′-tetramethylmaleonitrile were used to prepare derivatives of the 4,5-diamino-porphyrazine systems including the zinc(II) complexes. Subsequent oxidation of the macrocycles with potassium permanganate gave the corresponding seco-porphyrazines. These were shown to be efficient sensitizers for the production of singlet oxygen (Φ_Δ=0.15-0.57) by the determination of their photophysical properties.     

Evaluation of the activity of the sponge metabolites avarol and avarone and their synthetic derivatives against fouling micro- and macroorganisms

The sesquiterpene hydroquinone avarol (1) was isolated from the marine sponge Dysidea avara, whereas the corresponding quinone, avarone (2), was obtained by oxidation of avarol, and the significantly more lipophilic compounds [3'-(p-chloro-phenyl)avarone (3), 3',4'-ethylenedithioavarone (4), 4'-isopropylthioavarone (5), 4'-tert-butylthioavarone (6), 4'-propylthioavarone (7), 4'-octylthioavarone (8)] were obtained by nucleophilic addition of thiols or p-chloroaniline to avarone. All these compounds were tested, at concentrations ranging from 0.5 to 50 microg/mL, for their effect on the settlement of the cyprid stage of Balanus amphitrite, for toxicity to both nauplii and cyprids and for their growth inhibitory activity on marine bacteria (Cobetia marina, Marinobacterium stanieri, Vibrio fischeri and Pseudoalteromonas haloplanktis) and marine fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata and Monodictys pelagica).     

Synthesis of porphyrazine-octaamine, hexamine and diamine derivatives

The syntheses of a variety of substituted diaminomaleonitriles, with variable nitrogen substituents, were undertaken. Linstead macrocyclization of the resulting diaminomaleonitriles gave access to a wide range of functionalized porphyrazine-octaamines and hexamines and norphthalocyaninediamines. Conversion of these macrocycles into metallic derivatives and studies of their electronic absorption, solubility and electrochemistry are described. These flexible tetraazaporphyrins show potential in a range of applications including biomedical agents, novel charge-transfer complexes, chemical sensors, novel electronic materials and non-linear optics.     

Glandulaurencianols A–C,brominated diterpenes from the red alga, Laurencia glandulifera and the sea hare, Aplysia punctata

Glandulaurencianols A and B were isolated from the organic extract of the red alga, Laurencia glandulifera, collected from the island of Crete in South Greece. Investigation of the mollusk, Aplysia punctata, collected from the coast of Nea Makri, Central Greece, resulted in the isolation of glandulaurencianols A and C. The structures of the new metabolites, as well as their relative configurations, were established on the basis of thorough analyses of their spectroscopic data.     

Interrelations between Adsorption Energies and Local Isotherms, Local Monolayer Capacities, and Energy Distribution Functions, as Determined for Heterogeneous Surfaces by Inverse Gas Chromatography

Physicochemical parameters for adsorption of gases at the submonolayer regions of heterogeneous solid surfaces are measured experimentally as a function of time, and then interrelated as local isotherms θ against adsorption energy varepsilon, fractional changes of adsorption sites f(varepsilon)/c*(max) against varepsilon, θ against f(varepsilon)/c*(max), and distribution functions θ f(varepsilon)/c*(max) over adsorption energy values varepsilon, without using at all the well-known integral equation Theta(p, T)=integral(infinity)(0)θ(p, T, varepsilon)f(varepsilon)dvarepsilon and assumptions concerning the pair f(varepsilon) and θ(p, T, varepsilon). The method uses only chromatographic experimental data obtained by the inverse gas chromatography technique known as reversed-flow gas chromatography. It has been applied to the adsorption of cis-2-butene and trans-2-butene onto particles of Penteli marble at temperatures of 302, 314, 323, and 333 K. The results obtained are comparable with those calculated on the basis of the well-known integral equation. Copyright 2001 Academic Press.     

Novel Evidence-Based Combination of Plant Extracts with Multitarget Mechanisms of Action for the Elimination of Hot Flashes during Menopause

Hot flashes are considered the most bothersome complaint during menopause. Although hormone therapy is an effective option to relieve hot flashes, it has been associated with significant side effects. The aim of our study is to suggest a novel combination of different plant extracts with distinct mechanisms of action against hot flashes. We selected the rhizome of Glycyrrhiza glabra L. (Fabaceae), the rhizome of Actaea racemosa L. (Ranunculaceae), the aerial parts of Hypericum perforatum L. (Hypericaceae) to produce extracts rich in bioactive phytochemicals and the seed oil of Oenothera biennis L. (Onagraceae). We investigated their estrogenic and antioxidant potential and their inhibitory effect against prostaglandin D2 receptor 1 (DP1) as a novel mechanistic pathway for vasodilation in hot flashes, alone or in combination. The phytochemical footprint of the extracts was analyzed using HPLC-PDA and UPLC-HRMS. We observed that the tested extracts possess different mechanisms of action. A. racemosa exerts a beneficial activation of the estrogen receptor, H. perforatum possesses the highest antioxidant capacity and the seed oil of O. biennis inhibits the DP1 receptor. The triple combination in the optimal doses pertains to efficacy against all three mechanisms of action, serves as a multitarget plant-based therapy and could serve as a novel strategy for the alleviation of hot flashes in postmenopausal women.