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Polyphenolic enriched extracts from two species of Cyperus, Cyperus glomeratus and Cyperus thunbergii, possess mammalian arginase inhibitory capacities, with the percentage inhibition ranging from 80% to 95% at 100 µg/mL and 40% to 64% at 10 µg/mL. Phytochemical investigation of these species led to the isolation and identification of two new natural stilbene oligomers named thunbergin A-B (1–2), together with three other stilbenes, trans-resveratrol (3), trans-scirpusin A (4), trans-cyperusphenol A (6), and two flavonoids, aureusidin (5) and luteolin (7), which were isolated for the first time from C.thunbergii and C. glomeratus. Structures were established on the basis of the spectroscopic data from MS and NMR experiments. The arginase inhibitory activity of compounds 1–7 was evaluated through an in vitro arginase inhibitory assay using purified liver bovine arginase. As a result, five compounds (1, 4–7) showed significant inhibition of arginase, with IC50 values between 17.6 and 60.6 µM, in the range of those of the natural arginase inhibitor piceatannol (12.6 µM). In addition, methanolic extract from Cyperus thunbergii exhibited an endothelium and NO-dependent vasorelaxant effect on thoracic aortic rings from rats and improved endothelial dysfunction in an adjuvant-induced arthritis rat model.

International audience; The inhibition of arginase is of substantial interest for the treatment of various diseases of public health interest including cardiovascular diseases. Using an ex vivo experiment on rat aortic rings and an in vitro assay with liver bovine purified arginase, it was demonstrated that several polyphenolic extracts from Cyperus and Carex species possess vasorelaxant properties and mammalian arginase inhibitory capacities. Phytochemical studies performed on these species led to the identification of eight compounds, including monomers, dimers, trimers, and tetramers of resveratrol. The potential of these stilbenes as inhibitors of mammalian arginase was assessed. Five compounds, scirpusin B (5), ε-viniferin (4), cyperusphenol B (6), carexinol A (7), and the new compound virgatanol (1), showed significant inhibition of arginase, with percentage inhibition ranging from 70% to 95% at 100 μg/mL and IC50 values between 12.2 and 182.1 μM, confirming that these stilbenes may be useful for the development of new pharmaceutical products.

International audience; Dimeric stilbene glucosides 1-3 [two diastereomers of (-)-gnemonoside A (1a and 1b), (-)-gnemonoside C (2), and (-)-gnemonoside D (3)] as well as a mixture of the two enantiomers of gnetin C (4) were isolated from the rhizomes of Gnetum africanum. The two enantiomers of gnetin C, (+)-4 and (-)-4, were obtained from the aglycones of 1a and 1b, respectively. The configurations of these stilbenoids were investigated by NMR and vibrational circular dichroism (VCD) experiments. The absolute configurations of (-)-1a, (-)-2, (-)-3, and (-)-4 were established as 7aS,8aS by VCD spectroscopy in combination with density functional theory calculations. The antiamyloidogenic activity of the isolated stilbenes was also evaluated versus beta-amyloid fibrils. The four glucosides of gnetin C (1a, 1b, 2, and 3) were found to be the most active compounds, with inhibition percentages of 56, 56, 58, and 54 at 10 μM, respectively.

International audience; Neuroinflammatory processes are involved in the pathogenesis of many neurodegenerative disorders. Microglial cells, the main immune cells of the central nervous system, represent a target of interest to search for naturally occurring anti-inflammatory products. In this study, we evaluated the anti-inflammatory properties of polyphenols obtained from the stems of Morus alba. This edible species, known as white mulberry, is frequently studied because of its traditional use in Asian medicine and its richness in different types of polyphenols, some of which are known to be phytoalexins. One new coumarin glycoside, isoscopoletin 6-(6-O-β-apiofuranosyl-β-glucopyranoside) (1) was mainly isolated by CPC (centrifugal partition chromatography) from this plant, together with seven known polyphenols (2-8). Their structures were established on the basis of spectroscopic analyses including extensive 2D NMR studies. The eight isolated compounds were evaluated for their inhibitory activities on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 microglial cells. The absence of cell toxicity is checked by a MTT assay.

Stilbenes have received much attention during the last two decades following the discovery of resveratrol in wine. Since then, there have been a growing number of papers reporting various biological activities of naturally occurring stilbenes. The aim of this study was to determine new minor stilbenes from Vitis vinifera stalks. Purification of these compounds was achieved by means of centrifugal partition chromatography, a versatile separation technique that does not require a solid stationary phase. Viniphenol A (1), a new resveratrol hexamer, was isolated along with five oligostilbenoids identified in V. vinifera for the first time, ampelopsin C, davidiol A, leachianol F, leachianol G, and E-maackin, a dimer with an unusual dioxane moiety, and 14 known hydroxystilbenes. The structure and stereochemistry of viniphenol A were determined on the basis of spectroscopic data analysis and molecular modeling under NMR constraints. Viniphenol A showed protective effects against amyloid-β-induced toxicity in PC12 cell cultures.

Plants of the Carex genus (Family: Cyperaceae) have attracted recent attention as potential food additives due to their high levels of potential bioactive compounds. In this study, the stilbene contents of five unexplored Carex species were investigated: Carex capillacea, Carex hirta, Carex buchananii, Carex cuprina, Carex glauca. High-performance liquid chromatography coupled to mass spectrometry (HPLC–MS) and NMR spectroscopy (NMR) were used to identify the structures. A novel stilbene oligomer, carexinol A, was isolated together with five previously known stilbenes: resveratrol-diglucoside, miyabenol A and C, kobophenol A and α-viniferin. Furthermore, this is the first report of resveratrol diglucoside in Carex genus.