A new tripodal kojic acid derivative for iron sequestration: Synthesis, protonation, complex formation studies with Fe3+, Al3+, Cu2+ and Zn2+, and in vivo bioassays.

This work presents the simple and low cost synthesis of a new tripodal ligand, in which three units of kojic acid are coupled to a tris(2-aminoethyl)amine (tren) backbone molecule. The protonation equilibria, together with the complex formation equilibria of this ligand with Fe3+, Al3+, Cu2+ and Zn2+ ions were studied. The complementary use of potentiometric, spectrophotometric and NMR techniques, and of Density Functional Theory (DFT) calculations, has allowed a thorough characterization of the different species involved in equilibrium. The stability of the formed complexes with Fe3+ and Al3+ are high enough to consider the new ligand for further studies for its clinical applications as a chelating agent. Biodistribution studies were carried out to assess the capacity the ligand for mobilization of gallium in 67Ga-citrate injected mice. These studies demonstrated that this ligand efficiently chelates the radiometal in our animal model, which suggests that it can be a promising candidate as sequestering agent of iron and other hard trivalent metal ions. Furthermore, the good zinc complexation capacity appears as a stimulating result taking into a potential use of this new ligand in analytical chemistry as well as in agricultural and environmental applications.

Goniothalamin-Related Styryl Lactones: Isolation, Synthesis, Biological Activity and Mode of Action.

This review covers the chemistry and biological aspects of goniothalamin-related styryl lactones isolated from natural sources. This family of secondary metabolites has been reported to display diverse uses in folk medicine, but only a limited number of these compounds have been throughly investigated regarding their biological profile. Herein, we cover the goniothalamin-related styryl lactones having a C6-C3-C4 framework which appeared in the literature for the first time in the period 2000-2017, and the reports on the synthesis, biological activity and mechanism of action which were published from 2007-2017.

A Concise Synthesis of Rhodanthpyrone A and B, Natural 4-(Hydroxyphenyl)-substituted a-Pyrones.

A concise synthesis of rhodanthpyrone A and B was accomplished via a Suzuki coupling reaction. To find the conditions appropriate to install hydroxyphenyl moieties to the a-pyrone skeleton, a model study was conducted using commercially available boronic acids. It was revealed that the hydroxy moiety of the .pheriylboronic acids should be concealed when reacted with labile 4-tosyl α-pyrone. Consequently, rhodanthpyrone A and B could be synthesized in high. yields by Suzuki reaction using TIPS-protected arylboronic acids. This procedure provided a concise and versatile route for the synthesis of rhodanthpyrones and their 4-aryl substituted a-pyrone analogs.

Regulation of Anticancer Styrylpyrone Biosynthesis in the Medicinal Mushroom Inonotus obliquus Requires Thioredoxin Mediated Transnitrosylation of S-nitrosoglutathione Reductase.

The medicinal macrofungus Inonotus obliquus widely utilized as folk medicine in Russia and Baltic countries is a source of phenylpropanoid-derived styrylpyrone polyphenols that can inhibit tumor proliferation. Insights into the regulatory machinery that controls I. obliquus styrylpyrone polyphenol biosynthesis will enable strategies to increase the production of these molecules. Here we show that Thioredoxin (Trx) mediated transnitrosylation of S-nitrosoglutathione reductase (GSNOR) underpins the regulation of styrylpyrone production, driven by nitric oxide (NO) synthesis triggered by P. morii coculture. NO accumulation results in the S-nitrosylation of PAL and 4CL required for the synthesis of precursor phenylpropanoids and styrylpyrone synthase (SPS), integral to the production of styrylpyrone, inhibiting their activities. These enzymes are targeted for denitrosylation by Trx proteins, which restore their activity. Further, this Trx S-nitrosothiol (SNO) reductase activity was potentiated following S-nitrosylation of Trx proteins at a non-catalytic cysteine (Cys) residue. Intriguingly, this process was counterbalanced by Trx denitrosylation, mediated by Trx-dependent transnitrosylation of GSNOR. Thus, unprecedented interplay between Trx and GSNOR oxidoreductases regulates the biosynthesis of styrylpyrone polyphenols in I. obliquus.

Synthesis and biological evaluation of matrine derivatives containing benzo-α-pyrone structure as potent anti-lung cancer agents.

Matrine, an active component of root extracts from Sophora flavescens Ait, is the main chemical ingredient of Fufang Kushen injection which was approved by Chinese FDA (CFDA) in 1995 as an anticancer drug to treat non-small cell lung cancer and liver cancer in combination with other anticancer drugs. Owning to its druggable potential, matrine is considered as an ideal lead compound for modification. We delineate herein the synthesis and anticancer effects of 17 matrine derivatives bearing benzo-α-pyrone structures. The results of cell viability assays indicated that most of the target compounds showed improved anticancer effects. Further studies showed that compound 5i could potently inhibit lung cancer cell proliferation in vitro and in vivo with no obvious side effects. Moreover, compound 5i could induce G1 cell cycle arrest and autophagy in lung cancer cells through up-regulating P27, down-regulating CDK4 and cyclinD1 and attenuating PI3K/Akt/mTOR pathway. Suppression of autophagy attenuated 5i induced proliferation inhibition. Collectively, our results infer that matrine derivative 5i bears therapeutic potentials for lung cancer.

Dihydro-5,6-dehydrokavain (DDK) from Alpinia zerumbet: Its Isolation, Synthesis, and Characterization.

Dihydro-5,6-dehydrokavain (DDK) is the major and most promising component of the tropical plant Alpinia zerumbet (shell ginger), a species of the ginger family Zingiberaceae. Alpinia zerumbet is known for its human use as a traditional herbal medicine, food, and dietary supplement. With its α-lactone ring, DDK belongs to the large chemical group of kavalactones, which are also found in kava (Piper methysticum), another herbal medicine; DDK is characterized by a double-bond linkage at positions 5,6 and the absence of a double-bond linkage at positions 7,8. This dissociates DDK from other kavalactones with their linkages at positions 7,8 and 5,6 that are both either completely saturated or unsaturated, or may have an unsaturated bond at the position 7,8 as well as a saturated bond at the position 5,6. DDK is easily identified and quantified by HPLC and GC. DDK contents in fresh leaves, stems and rhizomes range from 80 to 410 mg/g, requiring solvent extraction procedures to ensure high DDK yield. This is best achieved by hexane extraction from fresh rhizomes that were previously boiled in water, allowing DDK yields of up to 424 mg/g. Successful synthesis of DDK can be achieved by asymmetric pathways, whereas its simple chemical structure facilitates the synthesis of DDK derivatives by HCl hydrolysis. Thus, all synthesized products may be used for various commercial purposes, including the potential development of promising antiobesity pharmaceutical drugs, preparation of specific and safe dietary supplements, and use as effective natural herbicides or fungicides.

Synthesis, Cytotoxic and Contraceptive Activity of 6,8,9-Trihydroxy-2-methyl-2H-naphtho[2,3-b]pyran-5,10-dione, a Pigment of Echinothrix diadema, and its Analogs.

6,8,9-Trihydroxy-2-methyl-2H-naphtho[2,3-b]pyran-5,10-dion, a pigment of the sea urchin Echinothrix diadema, and six analogs were synthesized. The cytotoxic activity and contraceptive properties of the synthesized pyranonaphthazarins have been investigated using the sperm and eggs of the sea urchin Strongylocentrotus intermedius.

Phthalide Anions in Organic Synthesis. A Direct Total Synthesis of Furomollugin.

Furomollugin was synthesized in three steps from commercially available starting materials using phthalide annulation chemistry.

Two novel innovanoside dimers from Daphne aurantiaca and a concise total synthesis of diinnovanoside A.

Chemical examination of the methanolic extract from the stem bark of Daphne aurantiaca led to the isolation of two innovanoside dimers (1 and 2) with an unusual four-membered cyclobutane ring, together with the isoinnovanoside 3. Their chemical structures and configurations were elucidated by extensive spectral analysis and synthesis.

Design, synthesis, in vitro cytotoxicity evaluation and structure-activity relationship of goniothalamin analogs.

A series of six/five member (E/Z)-Goniothalamin analogs were synthesized from commercially available (3,4-dihydro-2H-pyran-2-yl)methanol/5-(hydroxymethyl)dihydrofuran-2(3H)-one in three steps with good to moderate overall yields and their cytotoxicity against lymphoblastic leukemic T cell line (Jurkat E6.1) have been evaluated. Among the synthesized analogs, (Z)-Goniothalamin appeared to be the most active in cytotoxicity (IC50 = 12 µM). Structure-activity relationship study indicates that introducing substituent in phenyl ring or replacing phenyl ring by pyridine/naphthalene, or decreasing the ring size of lactones (from six to five member) do not increase the cytotoxicity.

Structure-anti-leukemic activity relationship study of ortho-dihydroxycoumarins in U-937 cells: key role of the δ-lactone ring in determining differentiation-inducing potency and selective pro-apoptotic action.

Previous studies indicated the need of at least one phenolic hydroxyl group in the coumarin core for induction of cytotoxicity in different cell lines. Herein, we present an exhaustive structure-activity relationship study including ortho-dihydroxycoumarins (o-DHC) derivatives, cinnamic acid derivatives (as open-chain coumarin analogues) and 1,2-pyrones (representative of the δ-lactone ring of the coumarin core), carried out to further identify the structural features of o-DHC required to induce leukemic cell differentiation and apoptosis in U-937 cells. Our results show for the first time that the δ-lactone ring positively influences the aforementioned biological effects, by conferring greater potency to compounds with an intact coumarin nucleus. Most tellingly, we reveal herein the crucial role of this molecular portion in determining the selective toxicity that o-DHC show for leukemic cells over normal blood cells. From a pharmacological perspective, our findings point out that o-DHC may be useful prototypes for the development of novel chemotherapeutic agents.

Hydroxy(thio)pyrone and hydroxy(thio)pyridinone iron chelators: physico-chemical properties and anti-oxidant activity.

The O,S-donor analogues of maltol and deferiprone (DMHP), respectively, thiomaltol and DMHTP, have been investigated in solution for their iron-complexation ability, as well as their electrochemical behaviors, in the presence and absence of iron, aimed at the rationalization of their anti-oxidant activity, particularly, as hydroxyl radical scavengers and inhibitors of lipid peroxidation. The results were compared with those of the O,O-donor compounds and revealed that all the compounds are good iron chelators (pFe=14.1-20.2), but the O,S-donor ligands being somewhat weaker than the corresponding oxo-analogues. Also all the ligands appear to be able to prevent the redox cycling of iron, a relevant anti-oxidant activity, which seems to be primary due to their high capacity to form iron complexes which are not effective in promoting free radical reactions. This is a significant feature for the development of leading analogues as drug candidates with co-adjuvant roles in oxidative-stress dependent pathologies.

Botcinolide/botcinin: asymmetric synthesis of the key fragments.

The asymmetric synthesis of key fragments of the phytotoxic toxins botcinolide/botcinin is reported. The synthesis of 1 and 1a are based on a convergent route via esterification and alkene metathesis of fragments A, B or C, B, which were obtained by Evans aldol condensation and stereoselective crotylation, respectively.

Theoretical investigation of the rubicordifolin cascade.

The results of a theoretical investigation on the complex cascade reaction leading to the natural product rubicordifolin are reported. These computations analyze the discrete transformations that are required during the conversion of the vinyl naphthoquinone starting material into the natural product, including two pseudopericyclic cyclizations as well as a diastereoselective, hetero-Diels-Alder reaction.

A study of cytotoxicity of novel chlorokojic acid derivatives with their antimicrobial and antiviral activities.

A series of 6-chloromethyl-3-hydroxy-2-substituted 4H-pyran-4-one derivatives were synthesized and tested for their antimicrobial and antiviral activities. Mannich base derivatives were prepared through the reaction of substituted piperazine or piperidine derivatives on chlorokojic acid and formaline. The structures of the synthesized compounds were confirmed by IR, (1)H and (13)C NMR, ESI-MS, and elemental analysis. According to the activity studies, compounds 2-7 (MIC: 1-2 microg/mL) were found to be highly active against Bacillus subtilis and Staphylococcus aureus, while compounds 3, 5 and 6 showed significant activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii. Also, compounds 2-7 were more remarkably active against Candida albicans and Candida parapsilosis (MIC: 4-8 microg/mL). Additionally, compound 2 was the most active one against RNA virus PI-3.

Efficient asymmetric total syntheses of cryptocarya triacetate, cryptocaryolone, and cryptocaryolone diacetate.

Concise and efficient asymmetric total syntheses of three substituted alpha-pyrone-type natural products have been accomplished via 7-9 steps from 5b in high overall yields, which involve linchpin coupling, ring-closing metathesis, and a tandem sequence of deacetylation and intramolecular oxa-Michael addition as the key steps.

Structure revision and synthesis of a novel labdane diterpenoid from Zingiber ottensii.

The structure of ottensinin, a recently reported constituent of the medicinal plant Zingiber ottensii, was revised by re-evaluation of available NMR data from alpha-ylidenebutenolide 1 to gamma-pyrone 2, whose rearranged labdane skeleton is unprecedented. Structure 2 was proven by synthesis from (+)-sclareolide (nine steps, 27% overall yield) and was further validated by X-ray diffraction analysis of our synthetic sample. A plausible biosynthesis of 2 is proposed.

Synthetic studies of neoclerodane diterpenes from Salvia divinorum: exploration of the 1-position.

Modification of the C-1 ketone of salvinorin A (2a) produces analogues with opioid antagonist properties. Of particular significance is the finding that 1-deoxo-1,10-dehydrosalvinorin A (11a) is a moderately potent antagonist at all three opioid receptor subtypes, and that herkinorin (2b), a mu agonist, is converted to a weak antagonist by removal of the C-1 ketone (3b and 11b). These observations suggest that the ketone of 2b is a key structural feature responsible for mu agonist activity.

Novel pyrone side tetracyclic psoralen derivatives: synthesis and photobiological evaluation.

This study reports the synthesis of tetrahydrobenzo- (4-6) and benzopsoralen (7-9) derivatives obtained by condensing the fourth ring to the pyrone side of the tricyclic psoralen moiety. The new compounds are characterized by having a methoxy, a hydroxy, or a dimethylaminopropoxy side chain inserted at position 8 of the psoralen chromophore. The evaluation of the photoantiproliferative activity on human tumor cell lines along with skin phototoxicity on guinea pigs revealed an interesting photobiological pattern for the dimethylaminopropoxy derivatives 6 and 9: they are in fact able to exert an antiproliferative effect up to 1 order of magnitude higher than that of the well-known drug 8-MOP, but they are devoid of skin phototoxicity. The ability of both 6 and 9 to photoadd to DNA is demonstrated by the isolation and characterization of the 4',5'-monoadducts. AM1 calculations were also performed to gain further insight into the molecular basis of their photobiological behavior.