benzofurans and quinone

Reversible redox processes involving hydroquinones and quinones are ubiquitous in biological reaction networks, materials science, and catalysis. While extensively studied in intermolecular settings, less is known about intramolecular scenarios. Herein, we report hydroquinone-quinone hybrid molecules that form two-stereocenter dihydrobenzofurans via intramolecular cyclization under thermodynamic control. A π-methylhistidine peptide-catalyzed kinetic resolution allowed us to study the stereodynamic behavior of enantio- and diastereo-enriched dihydrofurans. In the course of this study, it was revealed that a reversible intramolecular redox-interconversion network connects all four possible stereoisomers via inversion of a quaternary carbon stereocenter without achiral intermediates. As a result, these findings on hydroquinone-quinone hybrid molecules provide insights into potential natural origin and synthetic access of the common dihydrobenzofuran motif.

Topics: Benzofurans; Benzoquinones; Carbon; Catalysis; Hydroquinones; Models, Molecular; Oxidation-Reduction; Stereoisomerism

Foods of plant origin contain flavonoids. In the adzuki bean, (+)-catechin, quercetin 3-O-rutinoside (rutin), and quercetin 7-O-β-D-glucopyranoside (Q7G) are the major flavonoids. During mastication of foods prepared from the adzuki bean, the flavonoids are mixed with saliva and swallowed into the stomach. Here we investigated the interactions between Q7G and (+)-catechin at pH 2, which may proceed in the stomach after the ingestion of foods prepared from the adzuki bean. Q7G reacted with nitrous acid producing nitric oxide (˙NO) and a glucoside of 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone. (+)-Catechin reacted with nitrous acid producing ˙NO and 6,8-dinitrosocatechin. The production of the dinitrosocatechin was partly suppressed by Q7G, and the suppression resulted in the enhancement of Q7G oxidation. 6,8-Dinitrosocatechin reacted further with nitrous acid generating the o-quinone, and the quinone formation was effectively suppressed by Q7G. In the flavonoids investigated, the suppressive effect decreased in the order Q7G≈quercetin>kaempferol>quercetin 4'-O-glucoside>rutin. Essentially the same results were obtained when (-)-epicatechin was used instead of (+)-catechin. The results indicate that nitrous acid-induced formation of 6,8-dinitrosocatechins and the o-quinones can be suppressed by flavonols in the stomach, and that both a hydroxyl group at C3 and ortho-hydroxyl groups in the B-ring are required for efficient suppression.

Topics: Animals; Anticarcinogenic Agents; Benzofurans; Benzoquinones; Carcinogens; Catechin; Dietary Supplements; Digestion; Fabaceae; Functional Food; Gastric Juice; Glucosides; Humans; Models, Biological; Nitric Oxide; Nitroso Compounds; Nitrous Acid; Quercetin; Quinones; Saliva; Seeds; Stereoisomerism

The fruiting bodies or mycelia of mushrooms have been used as food and food-flavoring material for centuries due to their nutritional and medicinal value and the diversity of their bioactive components. The present research is the first to investigate the bioactive secondary metabolites from the solid culture of the edible mushroom Neolentinus lepideus. Two new secondary metabolites, 5-methoxyisobenzofuran-4,7(1H,3H)-dione (1) and 1,3-dihydroisobenzofuran-4,6-diol (2), as well as seven known compounds including one benzoquinone derivative (3) and six cinnamic acid derivatives (4-9) were obtained. Their structures were established by means of spectroscopic methods, including 1D and 2D NMR. The bioactivity on the nitric oxide production in lipopolysaccharide-induced macrophages was evaluated for all metabolites (1-9) isolated. Compound 1 showed strong NO inhibitory activity with the IC50 value of 6.2 μM. Compound 2 displayed moderate NO inhibitory activity with the IC50 value of 88.8 μM. In the DPPH scavenging assay, compound 2 displayed antioxidant activity with IC50 of 68.6 μM. The discovery of new NO production inhibitors from N. lepideus expands its usage as a functional food.

Topics: Agaricales; Benzofurans; Benzoquinones; Cell Line; Cell Proliferation; Humans; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Structure; Nitric Oxide; Plant Extracts; Vegetables