Synthesis and Antiradical Activity of Isoquercitrin Esters with Aromatic Acids and Their Homologues

Abstract

Isoquercitrin, (IQ, quercetin-3-O-β-d-glucopyranoside) is known for strong chemoprotectant activities. Acylation of flavonoid glucosides with carboxylic acids containing an aromatic ring brings entirely new properties to these compounds. Here, we describe the chemical and enzymatic synthesis of a series of IQ derivatives at the C-6″. IQ benzoate, phenylacetate, phenylpropanoate and cinnamate were prepared from respective vinyl esters using Novozym 435 (Lipase B from Candida antarctica immobilized on acrylic resin). The enzymatic procedure gave no products with “hydroxyaromatic” acids, their vinyl esters nor with their benzyl-protected forms. A chemical protection/deprotection method using Steglich reaction yielded IQ 4-hydroxybenzoate, vanillate and gallate. In case of p-coumaric, caffeic, and ferulic acid, the deprotection lead to the saturation of the double bonds at the phenylpropanoic moiety and yielded 4-hydroxy-, 3,4-dihydroxy- and 3-methoxy-4-hydroxy-phenylpropanoates. Reducing capacity of the cinnamate, gallate and 4-hydroxyphenylpropanoate towards Folin-Ciocalteau reagent was significantly lower than that of IQ, while other derivatives displayed slightly better or comparable capacity. Compared to isoquercitrin, most derivatives were less active in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, but they showed significantly better 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid, ABTS) scavenging activity and were substantially more active in the inhibition of tert-butylhydroperoxide induced lipid peroxidation of rat liver microsomes. The most active compounds were the hydroxyphenylpropanoates.

Sulfated Metabolites of Flavonolignans and 2,3-Dehydroflavonolignans: Preparation and Properties

“…Antiradical activity by 2,2-diphenyl-1-picrylhydrazyl [36] radical scavenging assay, reducing capacity using Folin–Ciocalteau reagent (FCR) [37], and anti-lipoperoxidant activity using inhibition of lipid peroxidation of rat liver microsomes induced by tert -butyl hydroperoxide [38] were determined as described previously with modifications described in detail in our previous research [5,23,39,40,41]. …”

“…N , N -dimethyl- p -phenylenediamine (DMPD) [ 33 ] and 2,2′-azino- bis (3-ethylbenzothiazolin-6-sulfonic acid (ABTS) [ 34 ] cation radical scavenging and ferric reducing antioxidant power (FRAP) [ 35 ] were measured using kits from Bioquochem (Llanera-Asturias, Spain). Antiradical activity by 2,2-diphenyl-1-picrylhydrazyl [ 36 ] radical scavenging assay, reducing capacity using Folin–Ciocalteau reagent (FCR) [ 37 ], and anti-lipoperoxidant activity using inhibition of lipid peroxidation of rat liver microsomes induced by tert -butyl hydroperoxide [ 38 ] were determined as described previously with modifications described in detail in our previous research [ 5 , 23 , 39 , 40 , 41 ].…”

Glucose Tolerance-Improving Activity of Helichrysoside in Mice and Its Structural Requirements for Promoting Glucose and Lipid Metabolism

“…In a similar procedure to that of 1 [31,32], compounds 3, 4, 5, 6, 7 [33], 8 [34], 10 [33], 12 [33,35,36 13) were also isomerized from 8, 10, and 12, respectively. Among these synthetic products, known compounds (1, 7, 8, 10, and 12) were identified by a comparison of their physicochemical data with those of authentic samples or with reported values.…”

“…The structures of 1 and 16 are similar: the former has a p-coumaroyl ester at the 6-position in the β-D-glucopyranosyl moiety of quercetin 3-O-β-d-glucopyranoside (isoquercitrin, 17), while the latter has the common acyl group at the same position of kaempferol 3-O-β-d-glucopyranoside (18). (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) and related compounds (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31).…”

Novel 1,3,4-Oxadiazole Derivatives Containing a Cinnamic Acid Moiety as Potential Bactericide for Rice Bacterial Diseases

“…As one of the natural aromatic fatty acids, cinnamic acid is the deaminated product of phenylalanine in plant tissues [ 9 ]. Substituted cinnamic acids show diverse biological activities, such as antitumor [ 9 ], antioxidation [ 10 , 11 ], insecticidal [ 12 ], antiviral [ 13 , 14 ], fungicidal [ 15 , 16 ], bactericidal [ 17 ], and herbicidal activities [ 18 ], and have attracted the attention of many researchers. In particular, many cinnamic acid analogs are crucial and promising compounds as potential antifungal and antibacterial agents [ 19 ].…”