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In this study, three series of chitosan derivatives bearing imidazole rings, including the Schiff‐bases of chitosan, N‐substituted chitosan, and quaternized chitosan are designed and synthesized. The structures of these chitosan derivatives are verified by FT‐IR and 1H NMR, and their antioxidant, antibacterial, and antifungal activities are tested. The Schiff‐bases of chitosan and N‐substituted chitosan have similar biological properties compared with chitosan. Derivatives 2IMTMC, 4IMTMC, MIMTMC, and BIMTMC exhibit significant antioxidant ability and antifungal activity, especially derivative BIMTMC. All the quaternized chitosan remarkably inhibits Escherichia coli, Staphylococcus aureus, and Vibrio harvey, especially derivative BIMTMC, whose minimum inhibitory concentration values are 0.03125, 0.0625, and 0.03125 mg mL−1, respectively. The results indicated that quaternized chitosan are synergistic with imidazole groups and have the better antioxidant, antifungal, and antibacterial properties than chitosan, which can be used as drug materials for antioxididant and antimicrobial purposes. [ABSTRACT FROM AUTHOR]

A series of pyrido[2,3- b ]pyrazin-3(4 H )-one based derivatives were designed as inhibitors of aldose reductase (ALR2), the enzyme which plays a key role in the development of diabetes complications as well as in the oxidative stress processes associated with diabetes and other pathologies. Most of the derivatives, having a substituted C2 aromatic group and a N4 acetic acid group on the core structure, were found to be potent and selective aldose reductase inhibitors with submicromolar IC 50 values, and 9c was the most active with IC 50 value 0.009 μM. Particularly, a number of the designed compounds bearing phenolic hydroxyl substituted C2-styryl side chain showed excellent not only in ALR2 inhibition but also in antioxidant, and among these 11i was proved to be the top one with an antioxidant ability even comparable to that of the well-known antioxidant Trolox. Structure-activity relationship and molecular docking studies highlighted the importance of phenolic hydroxyl substituents and vinyl spacer in C2 side chain of the scaffold for the construction of efficient and multifunctional ALR2 inhibitors. [ABSTRACT FROM AUTHOR]

Winter jujube ( Zizyphus jujuba Mill.) is a kind of high quality, fresh jujube fruit originated from China. Selenium (Se) affects the chemical composition and antioxidative properties in plants. At appropriate concentrations, Se acts as an antioxidant or activates mechanisms that can alleviate oxidative stress in the chloroplast, and enhances plant growth. Although the addition of Se is known to increase Se uptake in crops, it is unclear whether exogenous Se affects nutritional and functional components in winter jujube. Winter jujube trees were sprayed with selenium (as sodium selenite) at five concentrations (0, 25, 50, 100, or 200 mg/L of Se) three times at the fruitlet stage between July and August. The Se content, ratio of organic Se to total Se in leaves and fruits, fruit quality, and yield were measured. At Se concentrations of 50 mg/L or higher, total Se content increased rapidly whereas the ratio increased initially and decreased later. Different Se concentrations affected the quality of fruits differently: at 50 mg/L, compared to their values in the unsprayed control trees, vitamin C content was greater by 20.94%; soluble sugars, 29.48%; total flavonoids, 43.48%; and the sugar: acid ratio, 41.81%. Along with the increase of Se addition, average fruit weight and yield of winter jujube presented a trend of increasing up to 50 mg L −1 and decreasing thereafter. Thus, the foliar spray of sodium selenite at Se concentration of 50 mg/L is recommended during the fruitlet stage of Zhanhua winter jujube. [ABSTRACT FROM AUTHOR]

To enhance aldose reductase (ALR2) inhibition and add antioxidant ability, phenolic hydroxyl was introduced both to the quinoxalinone core and C3 side chain, resulting in a series of derivatives as ALR2 inhibitors. Biological activity tests suggested that most of the derivatives were potent and selective inhibitors with IC 50 values ranging from 0.059 to 6.825 μM, and 2-(3-(4-hydroxystyryl)-7-methoxy-2-oxoquinoxalin-1(2 H )-yl)acetic acid ( 6b ) was the most active. Particularly, it was encouraging to find that some derivatives endowed with obvious antioxidant activity, and among them the phenolic 3,4-dihydroxyl compound 6f with 7-hydroxyl in the quinoxalinone core showed the most potent activity, even comparable with the well-known antioxidant Trolox. Structure-activity relationship and docking studies highlighted the importance of phenolic hydroxyl both in C3 side chain and the core structure for constructing potent ALR2 inhibitors with antioxidant activity. [ABSTRACT FROM AUTHOR]

A series of aldose reductase (ALR2) inhibitors based on pyridothiadiazine were prepared and evaluated for their activities in ALR2 inhibition, DPPH scavenging, and MDA inhibition. Comparison studies were carried out between analogs having either hydroxyl or methoxy groups substituted on the N2-benzyl side chains of the compounds. Most of the hydroxy-substituted compounds were found to be more potent compared to their methoxy-substituted analogs with respect to DPPH inhibition (>93%) and MDA inhibition (>73%). However, ALR2 inhibitory activity was found to be affected by the electron-withdrawing substituent at the C7 position in addition to the effect of the N2-substituted benzyl group. These results provide an array of multifunctional ALR2 inhibitors possessing capacities both for ALR2 inhibition and as antioxidants. [ABSTRACT FROM AUTHOR]

A group of novel quinoxalinone derivatives ( 4a – h ) were prepared and investigated for their inhibitory activity against ALR2 and antioxidant activity. Most of them were found to be potent aldose reductase inhibitors with IC 50 values ranging from 0.019 to 0.982 μM. The most active compound 2-(3-(4-hydroxyphenoxy)-6-fluoro-2-oxoquinoxalin-1(2 H )-yl)acetic acid ( 4c ) also had an excellent selectivity. In addition, a number of compounds showed strong antioxidant activity and the phenolic 3,5-dihydroxyl compound 4f with 7-chloro in the quinoxalinone core was most active in scavenging the DPPH radical and suppressing lipid peroxidation. [ABSTRACT FROM AUTHOR]

Diabetic nephropathy (DN) is resulted from activations of polyol pathway and oxidative stress by abnormal metabolism of glucose, and no specific medication is available. We designed a novel class of benzoxazolone derivatives, and a number of individuals were found to have significant antioxidant activity and inhibition of aldose reductase of the key enzyme in the polyol pathway. The outstanding compound (E)-2-(7-(4-hydroxy-3-methoxystyryl)-2-oxobenzo[d]oxazol-3(2H)-yl)acetic acid was identified to reduce urinary proteins in diabetic mice suggesting an alleviation in the diabetic nephropathy, and this was confirmed by kidney hematoxylin-eosin staining. Further investigations showed blood glucose normalization, declined in the polyol pathway and lipid peroxides, and raised glutathione and superoxide dismutase activity. Thus, we suggest a therapeutic function of the compound for DN which could be attributed to the combination of hypoglycemic, aldose reductase inhibition and antioxidant. [Display omitted] • A novel class of benzoxazolone derivatives had significant activities in antioxidant and inhibition of aldose reductase. • Most potent one of them showed the activities in diabetic mice and also in blood glucose normalization. • An alleviation in diabetic nephropathy was confirmed by urinary proteins reduction and kidney hematoxylin-eosin staining. [ABSTRACT FROM AUTHOR]

Dihydrobenzoxazinone derivatives revealed potent activities of aldose reductase inhibition and antioxidant against diabetic complications. Dihydrobenzoxazinone based design and synthesis produced two series of compounds as aldose reductase (ALR2) inhibitor candidates. In particular, phenolic residues were embodied into the compounds for the combination of strengthening the inhibitory acitvity and antioxidant ability to retard the progression of diabetic complications. Most of the derivatives with styryl side chains exhibited excellent activities on selective ALR2 inhibition with IC 50 values ranging from 0.082 to 0.308 μM, and {8-[2-(4-hydroxy-phenyl)-vinyl]-2-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl}-acetic acid (3a) was the most potent. More significantly, most of dihydrobenzoxazinone compounds revealed not only good inhibitory effect on ALR2, but also showed powerful antioxidant activity. Notably, phenolic compound 3a was even comparable to the well-known antioxidant Trolox, confirming that the C8 p-hydroxystyryl substitution was key structure of lowering oxidative stress. Therefore, these results provided an achievement of multifunctional ALR2 inhibitors possessing capacities for both ALR2 inhibition and as antioxidants. [ABSTRACT FROM AUTHOR]