Isolation of flavonol rhamnosides from Pometia pinnata leaves and investigation of α-glucosidase inhibitory activity of flavonol derivatives (original) (raw)
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Journal of Enzyme Inhibition and Medicinal Chemistry, 2017
a-Glucosidase inhibitors are described as the most effective in reducing post-prandial hyperglycaemia (PPHG) from all available anti-diabetic drugs used in the management of type 2 diabetes mellitus. As flavonoids are promising modulators of this enzyme's activity, a panel of 44 flavonoids, organised in five groups, was screened for their inhibitory activity of a-glucosidase, based on in vitro structure-activity relationship studies. Inhibitory kinetic analysis and molecular docking calculations were also applied for selected compounds. A flavonoid with two catechol groups in A-and Brings , together with a 3-OH group at C-ring, was the most active, presenting an IC 50 much lower than the one found for the most widely prescribed a-glucosidase inhibitor, acarbose. The present work suggests that several of the studied flavonoids have the potential to be used as alternatives for the regulation of PPHG.
Journal of Functional Foods, 2021
Intensive investigation of phytochemicals from edible Melicope glabra leaves provided a series of O-alkylated quercetins (1–13). The quercetin 1 bearing prenyl and methyl motif showed potent inhibition to human acetylcholinesterase (hAChE) with mixed type I mode, while quercetin was inactive. The position of methyl group was also a critical factor to hAChE inhibition: 1 (4′-O-methyl, IC50 = 12.7 μM) vs 2 (3′-O-methyl, IC50 = 119 μM). Inhibitory potency was doubly confirmed with the binding affinity (KSV) based on fluorescence quenching. O-Methyl groups on quercetin were observed to influence β-secretase (BACE1) inhibition. Thus, O-methylated quercetins (4–6) displayed potential inhibitions against BACE1 with IC50 values of 1.3, 4.1, and 14.1 μM, respectively. All compounds (3–6) have noncompetitive mode to BACE1. Additionally, all quercetin derivatives (1–13) had antioxidant potentials against different radical sources (ABTS, ORAC and FRAP). The UPLC-ESI-Q-TOF/MS indicated that the ...
Foods
Flavonoids are a class of natural substances present in plants, fruits, vegetables, wine, bulbs, bark, stems, roots, and tea. Several attempts are being made to isolate such natural products, which are popular for their health benefits. Flavonoids are now seen as an essential component in a number of cosmetic, pharmaceutical, and medicinal formulations. Quercetin is the major polyphenolic flavonoid found in food products, including berries, apples, cauliflower, tea, cabbage, nuts, and onions that have traditionally been treated as anticancer and antiviral, and used for the treatment of allergic, metabolic, and inflammatory disorders, eye and cardiovascular diseases, and arthritis. Pharmacologically, quercetin has been examined against various microorganisms and parasites, including pathogenic bacteria, viruses, and Plasmodium, Babesia, and Theileria parasites. Additionally, it has shown beneficial effects against Alzheimer’s disease (AD), and this activity is due to its inhibitory e...
Inhibition of α-glucosidase bynewprenylated flavonoidsfrom euphorbia hirta L. herb
Post prandial hyperglycemia a b s t r a c t Ethnopharmacological relevance: Euphorbia hirta L. (Euphorbiaceae) is a pantropical medicinal rhizomatous herb, traditionally used in the treatment of diabetes, respiratory and gastro-intestinal disorders. Aim of the study: To isolate and characterize the constituents of Euphorbia hirta and evaluate their invitro α-glucosidase inhibitory activity. The study is also aimed at describing structural activity relationship, type of α-glucosidase inhibition and in-vivo potential to regulate post prandial hyperglycemia in Wistar rats. Materials and methods: Methanolic extract of whole plant was suspended in water, and sequentially fractionated with n-hexane and ethyl acetate. Further ethyl acetate fraction was subjected to medium pressure liquid chromatography (MPLC) to isolate the active molecules under the following experimental conditions, pressure (up to 5 kg/cm 2 ) and flow rate (2 in./min). The structural elucidation of isolated compounds was done on the basis of detailed spectral analysis. The α-glucosidase inhibitory potential of isolated compounds was evaluated and compared with standard drug acarbose. In addition, type of inhibition was dwelled by Lineweaver-Burk plot analysis. Further, sucrose tolerance test was performed in Wistar rats pre-treated with the isolated compounds and acarbose (0.015 mM) followed by a sucrose load (2 g/kg, p.o.) and blood glucose level was measured up to 120 min by the glucose oxidase method. Results: The ethyl acetate fraction afforded quercetrin (1), dimethoxy quercetrin (2), along with two new prenylated flavonosides designated as hirtacoumaroflavonoside (3) and hirtaflavonoside-B (4) characterized as 7-O-(p-coumaroyl)-5,7,4′-trihydroxy-6-(3,3-dimethyl allyl)-flavonol-3-O-β-D-glucopyranosyl-(2″-1″′)-O-α-L-rhamnopyranoside and 5, 7, 3′, 4′-trihydroxy-6-(3, 3-dimethyl allyl)-8-(iso-butenyl)-flavonol-3-C-β-D-glucopyranoside, respectively. All the isolated compounds showed dose dependent inhibition of α-glucosidase which was found to be comparable to acarbose. Maximum α-glucosidase inhibition was achieved with compound 3 (IC 50 0.022 mM) followed by 4 (IC 50 0.071 mM) in comparison to acarbose (IC 50 0.092 mM). The results revealed that 5,7,4′-trihydroxyflavone structure is imperative for the inhibitory activity. The prenylation in the flavonoids increase the potency and p-coumaroyl substitution at C-7 further enriched the α-glucosidase inhibition. Compound 3 exhibited non-competitive inhibition while compounds 1, 2 and 4 showed mixed non-competitive inhibitory pattern. The results of sucrose tolerance test corresponded well with the in vitro studies.
Tetrahedron Letters, 2017
Flavonoids constitute a large family of plant-derived polyphenolic compounds that are found in fruits, vegetables, spices, wines and juices 1. Examples of flavonoids include quercetin, fisetin, luteolin, apeginin, myricetin and many others. Previous studies have shown that these compounds exhibit an array of biological effects that are beneficial to humans, including antiviral, antioxidative, anti-inflammatory and anticarcinogenic. The solubility of these polyphenolic compounds can be increased through the modification of the chemical structure, which may improve oral bioavailability 2. As a result, considerable efforts have been directed towards the development of novel, highly soluble conjugates having clinical profiles that are similar or even superior to those exhibited by the parent molecules in vitro. These include synthetic esters, acyl
Antioxidant Activity of Quercetin: A Mechanistic Review
Turkish Journal of Agriculture - Food Science and Technology
Flavones and flavonoids are known to have potent antioxidant activity due to intracellular free radical scavenging capacities. Flavonoids are found ubiquitously in plants as a member of polyphenolic compounds which share diverse chemical structure and properties. Quercetin is among the most efficient antioxidants of the flavonoids. The antioxidant property of quercetin has been highlighted in this review. These compounds have pivotal role in treatment of diabetes, cancers and some cardiovascular diseases.
Free Radical Biology and Medicine, 2011
During the scavenging of free radicals flavonoids are oxidized to electrophilic quinones. Glutathione (GSH) can trap these quinones, thereby forming GSH-flavonoid adducts. The aim of this study was to compare the stability of the GSH-flavonoid adduct of 7-mono-O-(β-hydroxyethyl)rutoside (monoHER) with that of quercetin. It was found that GSH-quercetin reacts with the thiol N-acetyl-L-cysteine (NAC) to form NACquercetin, whereas GSH-monoHER does not react with NAC. In addition, the adduct of the monoHER quinone with the dithiol dithiothreitol (DTT) is relatively stable, whereas the DTT-quercetin adduct is readily converted into quercetin and DTT disulfide. These differences in reactivity of the thiol-flavonoid adducts demonstrate that GSH-monoHER is much more stable than GSH-quercetin. This difference in reactivity was corroborated by molecular quantum chemical calculations. Thus, although both flavonoid quinones are rapidly scavenged by GSH, the advantage of monoHER is that it forms a stable conjugate with GSH, thereby preventing a possible spread of toxicity. These findings demonstrate that even structurally comparable flavonoids behave differently, which will be reflected in the biological effects of these flavonoids.
Structure–antioxidant activity relationships of flavonoids isolated from different plant species
Food Chemistry, 2005
In the course of our phytochemical studies of different plants from developing countries we isolated and structurally characterized several flavonoid derivatives (compounds 1–26), both aglycones and glycosides, typical of the species investigated. The aim of this study was to evaluate varieties of medicinal plants that were growing in developing countries, known in traditional medicine as anti-inflammatory remedies, with respect to
On the antioxidant properties of three synthetic flavonols
Die Pharmazie, 2007
The antioxidant properties of a series of synthetic and natural flavonoids towards the oxygenated species superoxide radical anion (O 2 .-) enzimatically generated, were evaluated. 7-Hydroxyflavonol, 7,3 0-dihydroxyflavonol and 3 0-hydroxyflavonol were synthesised, with a systematic variation of the OH substitution on positions C3, C7, C3 0 and C4 0 , and their respective antioxidative abilities compared to those of the already characterised natural flavonoids quercetin, kaempferol and rutin. The efficiency of O 2 .-deactivation by the flavonoids does not correlate with their respective determined oxidation potentials, suggesting that the pure one-electron-transfer-mechanism of O 2 .-quenching could not be the main scavenging process involved. Experimental evidence demonstrated that the possible inhibition of the O 2 .-generator enzymatic system by the flavonoids must be disregarded as a possible indirect cause for the inhibition of the oxidative species. One possible mechanism for the inhibition of O 2 .-, highly dependent on the substitution pattern of the flavonoid, may be the generation of hydroperoxides or dioxetanes as oxidation products, as already postulated for other biologically relevant compounds. The simultaneous OH-substitution on positions C3 and C7 of the flavonoid skeleton plays a definitive role in the enhancement of the O 2 .-inhibitory effect. The replacement of OH by a O-rutinosyl group on position C7 suppresses at all that effect, whereas the absence of an OH group in position 7 significantly reduces the antioxidative power. Finally, the presence of OH groups on positions 3 0 and 4 0 does not produce any determinant effect in the antioxidative behaviour of the flavonoids.