Kinetic study of the reaction of thiophene-tocopherols with peroxyl radicals enlightenings the role of O˙⋯S noncovalent interactions in H-atom transfer.

Three new α-tocopherol thiophene derivatives were efficiently synthesized, characterized and used for the first time as chain-breaking antioxidants for the inhibition of the autoxidation of reference oxidizable substrates. The rate constant of the reaction with alkylperoxyl (ROO˙) radicals and the stoichiometry of radical trapping (n) for the thiophene-tocopherol compounds were determined by measuring the oxygen consumption during the autoxidation of styrene or isopropylbenzene, using a differential pressure transducer. The measurement of the reaction with ROO˙ radicals in an apolar solvent at 30 °C showed inhibition rate constants (kinh) in the order of 104 M-1 s-1. To rationalise the kinetic results, the effect of the thiophene ring on the H-atom donation by O-H groups of the functionalized tocopherols was investigated by theoretical calculations. The importance of noncovalent interactions (including an unusual O˙⋯S bond) for the stability of the conformers has been shown, and the O-H bond dissociation enthalpy (BDE(OH)) of these derivatives was determined. Finally, the photophysical properties of these new compounds were investigated to understand if the addition of thiophene groups changes the absorption or emission spectra of the tocopherol skeleton for their possible application as luminescent molecular probes.

Myrcene: A Natural Compound Showing Anticancer Activity in HeLa Cells.

γ-terpinene, α-terpinene, p-cymene, and myrcene are monoterpenes found in many essential oils extracted from a variety of plants and spices. Myrcene also occurs naturally in plants such as hops, cannabis, lemongrass, and verbena and is used as a flavoring agent in food and beverage manufacturing. In this research, the biological efficacy of γ-terpinene, α-terpinene, p-cymene, and myrcene was studied in human cell lines (HeLa, SH-SY5Y, and HDFa). Cytotoxicity, cell proliferation, cell migration, and morphology assays were performed to obtain detailed information on the anticancer properties. Our results show that myrcene has potential biological activity, especially in HeLa cells. In this cell line, it leads to an arrest of proliferation, a decrease in motility and morphological changes with loss of sphericity and thickness, and DNA damage. In addition, the interaction of γ-terpinene, α-terpinene, p-terpinene, and myrcene with calf thymus DNA (ct-DNA) was studied by UV-visible spectrophotometry. DNA binding experiments show that only myrcene can interact with DNA with an apparent dissociation constant (Kd) of 29 × 10-6 M.

Rhodium-catalyzed iminoiodane-mediated oxyamidation studies of 5-vinyluracil derivatives using aryl and alkyl sulfamates.

The dirhodium tetraacetate-catalyzed iminoiodane-mediated reaction of 1,3-dimethyl-5-vinyluracil with phenyl sulfamate provided a high yield of 5-(1-acetyl-2-phenylsulfamoyl)ethyluracil via regioselective nucleophilic ring opening by acetate anion of the transiently formed 5-(1,2)-N-phenylsulfonylaziridine intermediate. This 1,2-oxyamidation reaction was found to be general for a variety of aryl- and alkylsulfamates as well as for various 1,3-dialkyl-5-vinyluracil derivatives. Addition of an alcohol to the reaction mixture allowed formation of the corresponding 1-alkoxy products. A selection of the substituted uracil derivatives prepared by this procedure was evaluated for cytotoxic activities in HCT-116 and HepG2 cancer cell lines and showed either no or modest activities. Further evaluation for α-glucosidase inhibition revealed that compounds 15ca and 15da were more active than acarbose, the reference inhibitor. This methodology thus allows efficient preparation of highly functionalized uracil derivatives thereby providing a synthetic route to novel compounds with potentially useful biological activities.

Hydroperoxyl radical (HOO•) as a reducing agent: unexpected synergy with antioxidants. A review.

This review highlights the progress made in recent years in harnessing the peculiar chemistry of the hydroperoxyl, or perhydroxyl, radical (HOO•) during lipid peroxidation, particularly with regard to its interaction with antioxidants. The HOO• radical, the protonated form of superoxide, plays an important role in the propagation and termination of lipid peroxidation in nonaqueous systems. However, differently from alkylperoxyl (ROO•) radicals that have only oxidizing ability, HOO• has a two-faced oxidizing and reducing activity. The HOO• radical can reduce the radical of the antioxidant (phenols and aromatic amines) by H-atom transfer (A• + HOO• ⟶ AH + O2) thus increasing the length of the inhibition period and the effectiveness of the antioxidant. The simultaneous presence of HOO• and ROO• radicals triggers the catalytic antioxidant activity of quinones and nitroxides and explains the antioxidant activity of melanin-like polymers. The HOO• radical can be formed by fragmentation of ROO• radicals deriving from amines, alcohols, substituted alkenes and may be present at low concentrations in many oxidizing systems. Pro-aromatic compounds, like the natural essential oil component γ-terpinene, are the most effective sources of HOO• and behave as co-antioxidants in the presence of nitroxides or quinones. The future developments and applications of HOO• chemistry in the context of the inhibition of autoxidation are also discussed.

New insights into the biological activities of Chrysanthemum morifolium: Natural flavonoids alleviate diabetes by targeting α-glucosidase and the PTP-1B signaling pathway.

As dual regulators, the PTP-1B signaling pathway and α-glucosidase slow glucose release and increase the degree of insulin sensitivity, representing a promising therapeutic target for type 2 diabetes. In this study, we systematically examined the in vivo and in vitro anti-diabetic activities of natural flavonoids 1-6 from Chrysanthemum morifolium. Flavonoids 1-6 increased glucose consumption-promoting activity and the phosphorylation of GSK-3ß and Akt, and decreased PTP-1B protein level along with slightly inhibitory activity of the PTP-1B enzyme. Moreover, flavonoids 1-2 treatment induced insulin secretion in INS-1 cells. Besides, in vivo study revealed that flavonoids 2 and 5 demonstrated potent anti-hyperglycemic and anti-hyperlipidemic activity, and improved maltose and glucose tolerance. Although flavonoid 2 exhibited lower inhibitory activity against α-glucosidase in vitro, it could deglycosylated in vivo to diosmetin to function as an α-glucosidase inhibitor. Taken together, these results led to the identification of the natural flavonoids 1-6 from C. morifolium as dual regulators of α-glucosidase and the PTP-1B signaling pathway, suggesting their potential application as new oral anti-diabetic drugs or functional food ingredients.

Synthesis & α-glucosidase inhibitory & glucose consumption-promoting activities of flavonoid-coumarin hybrids.

AIM: The research of novel and potent antidiabetic agents is urgently needed for the control of the exploding diabetic population. We previously reported the synthesis and antidiabetic activity of natural 8-(6"-umbelliferyl)-apigenin (1), but its antidiabetic targets are not known. Therefore, four series of derivatives were synthesized and evaluated for their antidiabetic activities. Results & methodology: Compounds (5a) and (14a) were identified as new α-glucosidase and α-amylase dual inhibitors. The kinetic analysis of the most potent α-glucosidase inhibitor of each series of compounds revealed that they inhibited α-glucosidase in irreversible modes. In addition, compounds (5a) and (14a) showed potent glucose consumption-promoting activity. CONCLUSION: Compounds (5a) and (14a) could be regarded as promising starting points for the development of antidiabetic candidates.