Research has shown that chitosan induces plant stress tolerance and protection, but few studies have explored chemical modifications of chitosan and their effects on plants under water stress. Chitosan and its derivatives were applied (isolated or in mixture) to maize hybrids sensitive to water deficit under greenhouse conditions through foliar spraying at the pre-flowering stage. After the application, water deficit was induced for 15 days. Analyses of leaves and biochemical gas exchange in the ear leaf were performed on the first and fifteenth days of the stress period. Production attributes were also analysed at the end of the experiment. In general, the application of the two chitosan derivatives or their mixture potentiated the activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase at the beginning of the stress period, in addition to reducing lipid peroxidation (malonaldehyde content) and increasing gas exchange and proline contents at the end of the stress period. The derivatives also increased the content of phenolic compounds and the activity of enzymes involved in their production (phenylalanine ammonia lyase and tyrosine ammonia lyase). Dehydroascorbate reductase and compounds such as total soluble sugars, total amino acids, starch, grain yield and harvest index increased for both the derivatives and chitosan. However, the mixture of derivatives was the treatment that led to the higher increase in grain yield and harvest index compared to the other treatments. The application of semisynthetic molecules derived from chitosan yielded greater leaf gas exchange and a higher incidence of the biochemical conditions that relieve plant stress.

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Background: Sulfonamides have been in clinical use for many years and the development of bioactive substances containing the sulfonamide subunit has grown steadily in view of their important biological properties such as antibacterial, antifungal, antiparasitic, antioxidant and antitumour properties. Objective: This review addresses the medicinal chemistry aspects of sulfonamides; covering their discovery, the structureactivity relationship and the mechanism of action of the antibacterial sulfonamide class, as well as the physico-chemical and pharmacological properties associated with this class. It also provides an overview of the various biological activities inherent to sulfonamides, reporting research that emphasises the importance of this group in the planning and development of bioactive substances, with a special focus on potential antitumour properties. Discussion: The synthesis of sulfonamides is considered to be simple and provides a diversity of derivatives from a wide variety of amines and sulfonyl chlorides. The sulfonamide group is a non-classical bioisostere of carboxyl groups, phenolic hydroxyl groups and amide groups. This review highlights that most of the bioactive substances have the sulfonamide group, or a related group such as sulfonylurea, in an orientation towards other functional groups. This structural characteristic was observed in molecules with distinct antibacterial activities, demonstrating a clear structureactivity relationship of sulfonamides. Conclusion: This short review sought to contextualise the discovery of classic antibacterial sulfonamides and their physico-chemical and pharmacological properties. The importance of the sulfonamide subunit in Medicinal Chemistry has been highlighted and emphasised, in order to promote its inclusion in the planning and synthesis of future drugs.

New Mannich base-type eugenol derivatives were synthesized and evaluated for their anticandidal activity using a broth microdilution assay. Among the synthesized compounds, 4-allyl-2-methoxy-6-(morpholin-4-ylmethyl) phenyl benzoate (7) and 4-{5-allyl-2-[(4-chlorobenzoyl)oxy]-3-methoxybenzyl}morpholin-4-ium chloride (8) were found to be the most effective antifungal compounds with low IC50 values, some of them well below those of reference drug fluconazole. The most significant IC50 values were those of 7 against C. glabrata (1.23 μm), C. albicans and C. krusei (both 0.63 μm). Additionally, the synthesized compounds were evaluated for their in vitro cytotoxic effects on human mononuclear cells. As result, the cytotoxic activity of eugenol in eukaryotic cells decreased with the introduction of the morpholinyl group. Given these findings, we point out compounds 7 and 8 as the most promising derivatives because they showed potency values greater than those of eugenol and fluconazole and they also presented high selectivity indexes.

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