Phosphodiesterase 5 and Arginase Inhibitory Activities of the Extracts from Some Members of Nelumbonaceae and Nymphaeaceae Families.

The objectives of this study were (1) to investigate the effect of extracts from some plants in the families Nelumbonaceae and Nymphaeaceae on phosphodiesterase 5 (PDE5) and arginase, which have been used in erectile dysfunction treatment, and (2) to isolate and identify the compounds responsible for such activities. The characterization and quantitative analysis of flavonoid constituents in the active extracts were performed by HPLC. Thirty-seven ethanolic extracts from different parts of plants in the genus Nymphaea and Victoria of Nymphaeaceae and genus Nelumbo of Nelumbonaceae were screened for PDE5 and arginase inhibitory activities. The ethanolic extracts of the receptacles and pollens of Nelumbo nucifera Gaertn., petals of Nymphaea cyanea Roxb. ex G.Don, Nymphaea stellata Willd., and Victoria amazonica (Poepp.) Sowerby and the petals and receptacles of Nymphaea pubescens Willd. showed IC50 values on PDE5 of less than 25 µg/mL while none of the extracts showed effects on arginase. The most active extract, N. pubescens petal extract, was fractionated to isolate and identify the PDE5 inhibitors. The results showed that six flavonoid constituents including quercetin 3'-O-ß-xylopyranoside (1), quercetin 3-methyl ether 3'-O-ß-xylopyranoside (2), quercetin (3), 3-O-methylquercetin (4), kaempferol (5) and 3-O-methylkaempferol (6) inhibited PDE5 with IC50 values at the micromolar level.

Mammalian Arginase Inhibitory Activity of Methanolic Extracts and Isolated Compounds from Cyperus Species.

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.

Polyphenolic compounds of Euphorbia umbellata (Pax) Bruyns (Euphorbiaceae) improved endothelial dysfunction through arginase inhibition.

Euphorbia umbellata is used for its anti-inflammatory properties; however, there are limited data available regarding its effects on vascular function. Its bark is rich in polyphenolic compounds, which potentially improve endothelial dysfunction (ED). This study proposes to investigate the effects of E. umbellata bark extracts and its polyphenolic compounds on arginase (ARG) activity and nitric oxide (NO)-related targets. Chromatographic procedures were used for the chemical characterisation of the extracts. Furthermore, in silico (molecular docking), in vitro (ARG inhibition), in vivo (streptozotocin-induced hyperglycemia model), and ex vivo (l-arginine metabolism, vascular reactivity, western blot, and biochemical) techniques were carried out. Quercetin, gallic acid, and ellagic acid were identified in the extracts. In silico screening predicted that gallic acid and quercetin would have the most promising interactions with ARG -identified cavities. This was confirmed in vitro as both compounds had a direct inhibitory effect on ARG, as was the case regarding the extracts. Oral treatment preserved endothelium-dependent vasodilation through ARG inhibition together with an increase in l-arginine bioavailability and endothelial NO synthase expression. Biochemical parameters determined the lack of toxicity for sub-chronic treatment. E. umbellata bark extracts and its compounds can contribute to ED treatment, at least partly, through the inhibition of vascular ARG.

Arginase inhibitory properties of flavonoid compounds from the leaves of Mulberry (Morus alba, Moraceae).

OBJECTIVES: We aimed to isolate and identify bioactive molecules from Morus alba (Moraceae) leaves having arginase inhibitory activity towards the combat of clinical outcomes related to endothelial dysfunction. METHOD: Extraction and isolation were carried out by successive macerations, prepurification by using a Solid Phase Extraction (SPE) and separation using preparative PLC. The structures of the isolated components were established and confirmed by spectroscopic analyses, including the ESI-HRMS and NMR spectroscopic investigations. Biological evaluation was performed by using an in vitro assay with liver bovine purified arginase and by an ex vivo aortic ring study. KEY FINDINGS: We demonstrated that a phenolic extract from the leaves of M. alba possesses mammalian arginase inhibitory capacities. Investigation of the chemical constituents of its leaves results in the isolation and identification of ten compounds investigated in vitro for their arginase inhibitory capacities. Four compounds showed significant inhibition of arginase, with percentage inhibition ranging from 54% to 83% at 100 µm. In isolated rat aortic rings incubated with NO synthase inhibitor, Luteolin-7-diglucoside compound (2) was able to increase acetylcholine-induced relaxation. CONCLUSIONS: These results demonstrated the attractive ability of M. alba to be a potential source for the discovery of new active products on vascular system.

Thin-layer chromatography-bioautographic method for the detection of arginase inhibitors.

Arginase represents a promising therapeutic target for various pathologies including inflammatory, cardiovascular, and parasitic diseases or cancers. In the current work, we report, for the first time, about the development of a thin-layer chromatography-based bioautography which can be used to rapidly detect arginase inhibitors in complex matrices such as plant extracts. The assay is based on the detection of urea produced by arginase using the coloring reagent α-isonitrosopropiophenone, resulting in the formation of a pink background on thin-layer chromatography plates. The assay conditions were optimized in order to provide sufficient contrast between the pink colored thin-layer chromatography plate and the clearer zones generated by the presence of arginase inhibitors. Different parameters were tested, such as incubation time and temperature, atmospheric conditions, as well as substrate and enzyme concentrations. This technique makes it possible to detect 0.1 µg of a known arginase inhibitor, Nω -hydroxy-nor-Arginine, after it has been spotted, either pure or mixed with a Myrtus communis methanolic fruit extract, and the plate has been developed in an appropriate solvent. The newly developed method was used to reveal the presence of an inhibitor in hempseed cakes (Cannabis sativa L.).

Vasorelaxant effects of Crataegus pentagyna: Links with arginase inhibition and phenolic profile.

ETHNOPHARMACOLOGICAL RELEVANCE: Crataegus leaves, flowers and fruits have been traditionally used to improve blood circulation, numerous preclinical and clinical studies supporting the cardiovascular benefits of Crataegus preparations. In this respect, there is very limited data on Crataegus pentagyna; in addition, the chemical profile of this species is still incompletely elucidated. AIM OF THE STUDY: The objective of this study was to examine the cardiovascular benefits of Crataegus pentagyna Waldst. et Kit. ex Willd. (small-flowered black hawthorn, Rosaceae) extracts (leaf, flower and fruit ethyl acetate extracts) and the underlying mechanisms. We hypothesized that C. pentagyna extracts might exert vasodilatory effects and inhibit arginase activity due, in large part, to their polyphenolic constituents. MATERIALS AND METHODS: C. pentagyna extracts induced-relaxation and the mechanisms involved were studied ex vivo in isolated aortic rings from Sprague-Dawley rats. The inhibitory effects on bovine liver arginase I were assessed by an in vitro assay. Metabolite profiling of C. pentagyna extracts was performed and the most endothelium- and nitric oxide synthase-dependent; flower extract additionally reduced Ca2+ entry and, to a lesser extent, Ca2+ release from the sarcoplasmic reticulum. C. pentagyna proved to be an important source of arginase inhibitors with potential benefits in endothelial dysfunction that remains to be explored.

Metabolite profiling, arginase inhibition and vasorelaxant activity of Cornus mas, Sorbus aucuparia and Viburnum opulus fruit extracts.

The present study investigated the effects of Cornus mas, Sorbus aucuparia and Viburnum opulus fruit extracts on arginase activity and arterial vasodilation. V. opulus fruit extract exerted the highest vasorelaxant activity in phenylephrine precontracted rat aortic rings (EC50 = 6.31 ±â€¯1.61 µg/mL) and a significant inhibition of arginase (IC50 = 71.02 ±â€¯3.06 µg/mL). By contrast, S. aucuparia and C. mas fruit extracts showed no important anti-arginase activity and a significantly weaker activity in the rat aortic rings relaxation assay (EC50 = 100.9 ±â€¯11.63 and 78.52 ±â€¯8.59 µg/mL, respectively). For all extracts, the main mechanism of vasodilation was proven to be endothelium-dependent. HPLC-ESI-Q-TOF-MS/MS studies revealed a very complex metabolite profiling in all three extracts with chlorogenic acid accounting for 30.89, 0.72 and 2.03 mg/g in V. opulus, C. mas and S. aucuparia fruit extracts, respectively. All extracts were declared non-toxic in the brine shrimp acute toxicity test. Our study highlights potential benefits of V. opulus fruit extract in diseases associated with endothelial dysfunction and impaired vasodilation.