Enzo Santaniello

Cytokinins, plant hormones derived from adenine, are best known for regulating growth and stress responses in plants. Recent findings suggest they may also influence microbial viability, yet their direct antimicrobial potential remains underexplored. This study evaluates the antimicrobial activities of four natural cytokinins (iPA, B, K, and p-T) and their N⁹-ribosides (iPAR, BR, KR, and p-TR) against selected human pathogens. Using the broth microdilution method, we assessed their effects on Gram-positive and Gram-negative bacteria, as well as fungal strains. While Gram-negative species showed no susceptibility, all tested compounds exhibited bacteriostatic activity against Bacillus subtilis and Enterococcus faecalis. Most notably, kinetin (K) and kinetin riboside (KR) displayed strong antifungal activity against Candida albicans, with MIC values comparable to the reference drug nystatin. Molecular docking studies supported these findings by showing that K and KR form favorable interactions with two validated antifungal targets in Candida albicans: secreted aspartic proteinase 3 (SAP3) and dihydrofolate reductase (DHFR). This is, to our knowledge, the first report linking natural cytokinins to direct antifungal action against C. albicans supported by in silico evidence. These findings highlight the potential of K and KR as promising leads for the development of cytokinin-based antifungal agents.

2-Cyano-6-hydroxybenzothiazole is the key intermediate for the synthesis of d-luciferin, the natural substrate of firefly luciferases. A new synthesis of 2-cyano-6-hydroxybenzothiazole has been realized starting from the reaction of 1,4-benzoquinone with l-cysteine ethyl ester, followed by oxidation-cyclization of the intermediate ethyl (R)-2-amino-3-(2,5-dihydroxyphenylsulfanyl)propan­oate hydrochloride to 2-carbethoxy-6-hydroxybenzothiazole. A suitable protection of this intermediate and a conversion to the corresponding nitrile gave, after deprotection, 2-cyano-6-hydroxybenzothiazole (32% yield from 1,4-benzoquinone). This nitrile reacts with d-cysteine to afford d-luciferin at room temperature in nearly quantitative yield (90-95%).

Peroxynitrite is the product of the reaction of nitric oxide with superoxide radical and is implicated in the pathogenesis of a wide variety of human diseases, being responsible for in-vivo oxidation/nitration events. Nitrosoperoxycarbonate anion, formed by the interaction of peroxynitrite with CO2/bicarbonate at physiological concentrations, provides a new interpretation of oxidative/nitrative processes formerly attributed to peroxynitrite. The aim of this review is to summarize the chemistry and biology of peroxynitrite and radical species related to nitrosoperoxycarbonate anion, as well as the information available regarding the molecular mechanisms that determine and regulate radical-promoted injury by the two tightly connected species at physiological concentrations. Interception of carbonate and nitro radicals produced by interaction of peroxynitrite with CO2/bicarbonate, as in-vivo prevention of pathological events, creates new perspectives for the evaluation of safe scavengers of oxidative/nitrative stress at the physiological level. In this respect, natural products such as flavonoids hold a preeminent position among the vast array of compounds endowed with such properties.

4-Hydroxy-2-nonenal (HNE) has been prepared from the corresponding dimethylacetal (HNE-DMA), in turn synthesized by a conventional approach with a few modifications of the experimental protocol and some improvements in the purification of the final product. In order to exploit the sensitivity of gas-chromatography with electron capture detector (GC-ECD) in the analysis of HNE derivatives, reaction of HNE with 2,4,6-trichlophenylhydrazine (TCPH) and 3,5-dichloro-phenylhydrazine (DCPH) was tested. Reaction with TCPH afforded a mixture of products, whereas with DCPH a single major product was formed that was prepared on a millimolar scale and purified. (1)H-NMR analysis established that the derivative of HNE with DCPH is HNE 3,6-dichloro-phenylhydrazone, that can be used as standard for GC-ECD analysis.