The cerebrospinal fluid melatonin is released from the pineal gland, directly into the third ventricle, or produced de novo in the brain from extrapineal melatonin sources leading to a melatonin concentration gradient in the cerebrospinal fluid. Despite the interest on this topic, the brain areas capable of producing melatonin are not yet clear. Bearing this in mind, we hypothesized that the choroid plexus (CP) could be one of these melatonin sources. We analyzed and confirmed the presence of the four enzymes required for melatonin synthesis in rat CP and demonstrated that arylalkylamine N‐acetyltransferase shows a circadian expression in female and male rat CP. Specifically, this enzyme colocalizes with mitochondria in rat CP epithelial cells, an organelle known to be involved in melatonin function and synthesis. Then, we demonstrated that melatonin is synthesized by porcine CP explants, although without a circadian pattern. In conclusion, our data show that the CP is a local source of melatonin to the central nervous system, probably contributing to its high levels in the cerebrospinal fluid. We believe that in the CP, melatonin might be regulated by its endogenous clock machinery and by the hormonal background.

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Several naturally occurring cyclopentenones, such as palmenones and nigrosporiones, exhibit antimicrobial activity. Herein we describe the antimicrobial activity of cyclopentenones and derivatives that can be easily accessed from biomass derivatives furfural and 5‐hydroxymethylfurfural. Upon screening a range of functionalized trans‐diamino‐cyclopentenones (DCPs) and δ‐lactone‐fused cyclopentenones (LCPs), an oxime ether derivative of DCP was identified that exhibited remarkable antimicrobial activity against Gram‐positive bacteria, including resistant strains such as methicillin‐resistant S. aureus (MRSA) and vancomycin‐resistant E. faecalis (VRE) strains.

The demand for new biomass-derived fine and commodity chemicals propels the discovery of new methodologies and synthons. Whereas furfural and 5hydroxymethylfurfural are cornerstones of sustainable chemistry, 3-acetamido-5-acetyl furan (3A5AF), an Nrich furan obtained from chitin biomass, remains unexplored, due to the poor reactivity of the acetyl group relative to previous furanic aldehydes. Here we developed a reactive 3-acetamido-5-furfuryl aldehyde (3A5F) and demonstrated the utility of this synthon as a source of bio-derived nitrogen-rich heteroaromatics, carbocycles, and as a bioconjugation reagent.