Quinoxalin-2(1H)-one based design and synthesis produced several series of aldose reductase (ALR2) inhibitor candidates. In particular, phenolic structure was installed in the compounds for the combination of antioxidant activity and strengthening the ability to fight against diabetic complications. Most of the series 6 showed potent and selective effects on ALR2 inhibition with IC50 values in the range of 0.032-0.468 μM, and 2-(3-(2,4-dihydroxyphenyl)-7-fluoro-2-oxoquinoxalin-1(2H)-yl)acetic acid (6e) was the most active. More significantly, most of the series 8 revealed not only good activity in the ALR2 inhibition but also potent antioxidant activity, and 2-(3-(3-methoxy-4-hydroxystyryl)-2-oxoquinoxalin-1(2H)-yl)acetic acid (8d) was even as strong as the well-known antioxidant Trolox at a concentration of 100 μM, verifying the C3 p-hydroxystyryl side chain as the key structure for alleviating oxidative stress. These results therefore suggest an achievement of multifunctional ALR2 inhibitors having both potency for ALR2 inhibition and as antioxidants.

Sulfonyl group-containing compounds constitute an important class of therapeutical agents in medicinal chemistry presumably because of the tense chemical structure and functionality of the sulfonyl, which could not only form hydrogen bonding interactions with active site residues of biological targets but also, as incorporated into core ring structure, constrain the side chains and allowed their specific conformations that fit the active sites. This review focuses on sulfonamides and sulfones, which cover more than 40 series and are associated with at least 10 potential pharmaceutical targets in pathways of glucose metabolism and insulin signaling. A large number of such compounds have been reported as pharmaceuticals every year in the last decade. In particular, increasing studies suggest that sulfonamides and sulfones play a key role in the design of pharmaceutical agents with potential application for the treatment of diabetes and its complications. First, they are inhibitors of a variety of enzymes including 11β-hydroxysteroid dehydrogenase type 1, α- glucosidase, carnitine palmitoyltransferase and cytosolic phosphoenolpyruvate carboxykinase, and in turn involved in the regulation of the metabolism of glucose. In addition, they are active as activators of glucokinase and as antagonists of ghrelin receptors. These enzyme and receptors are tightly associated with the regulation of glucose metabolism and the improvement of insulin resistance. Secondly, sulfonamides and sulfones act in the insulin secretion. As agonists, they activate insulin receptor tyrosine kinase and thus increase insulin sensitivity. Moreover, they as inhibitors suppress protein tyrosine phosphatase 1B and dipeptidyl peptidase IV, and thus normalize the insulin signaling pathway. Finally, a number of sulfonamides and sulfones are inhibitors of aldose reductase, which have been linked to diabetic complications.

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Infection by Macrophonina phaseolina was substantially reduced following treatment of sunflower and mungbean seeds with Trichoderma harzianum, Gliocladium virens, Paecilomyces lilacinus or Streptomyces sp. which gave promising control of charcoal rot disease. Treatment of mungbean seeds with Rhizobium meliloti also gave good disease control.

A novel and facile synthesis of quinoxalinone derivatives was developed in which a wide range of 3-chloroquinoxalin-2(1H)-ones as key intermediates can be generated chemo- and regioselectively in good yields from corresponding quinoxaline-2,3(1H,4H)-diones. This new protocol is arguably superior, as it allows the design and preparation of a variety of bioactive quinoxaline-based compounds, which are particularly effective in the treatment of diabetes and its complications. Through this procedure, a new class of quinoxalinone-based aldose reductase inhibitors were synthesized successfully. Most of the inhibitors, with an N1-acetic acid head group and a substituted C3-phenoxy side chain, proved to be potent and selective. Their IC(50) values ranged from 11.4 to 74.8 nM. Among them, 2-(3-(4-bromophenoxy)-7-fluoro-2-oxoquinoxalin-1(2H)-yl)acetic acid and 2-(6-bromo-3-(4-bromophenoxy)-2-oxoquinoxalin-1(2H)-yl)acetic acid were the most active. Structure-activity relationship and molecular docking studies highlighted the importance of the ether spacer in the C3-phenoxy side chains, and provided clear guidance on the contribution of substitutions both at the core structure and the side chain to activity.

The transformation of the antibacterial diterpene sclareol (1) by two different fungal strains was investigated (Scheme). In the presence of Rhizopus stolonifer, (3beta)-3-hydroxysclareol (2), 18-hydroxysclareol (3), (6alpha)-6,18-dihydroxysclareol (4), and (11S)-11,18-dihydroxysclareol (5) were formed. Fermentation of 1 with Fusarium lini afforded (1beta)-1-hydroxysclareol (6) and (12S)-12-hydroxysclareol (7). Compounds 4-7 were identified as new compounds, and some of them were active against Bacillus subtilis (Table 3).

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