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Boldine ((S)-2,9-dihydroxy-1,10-dimethoxy-aporphine) has been defined as the major alkaloid in Chilean boldo tree. Besides its diverse pharmacological activities, e.g. neuroprotective, cytoprotective, anti-inflammatory activities, boldine also exhibits tyrosinase-inhibiting effect. Tyrosinase [EC 1.14.18.1] is well known as a bifunctional enzyme that is responsible for the melanin biosynthesis. Considering the diphenolic structural feature of the alkaloid, which is associated with its tyrosinase inhibitory properties, herein we first modified the boldine core and then linked it with the natural phenolic antioxidants such as: caffeic-, ferulic- and sinapic acids. Furthermore, the newly amides were tested in vitro on the mushroom tyrosinase. Our results indicated, that amongst the tested boldine derivatives, caffeoyl- and feruloylamides have shown the anti-tyrosinase activity closely correlated with a hydroquinone, used as a standard. [ABSTRACT FROM AUTHOR]

A series of amides was synthesized by coupling of 3-aminomethylglaucine with various amino acid analogues. The reaction was carried out under mild conditions by using various carbodiimides and in the presence of catalytic amount of N-hydroxybenzotriazole. Five of the compounds obtained were new, and their spectral data are presented and discussed here. Selected amides were tested for their ability to scavenge the stable free 1,1-diphenyl-2-picryl-hydrazyl (DPPH●) radical. The most active compounds were N-sinapoylphenylalanyl-3-aminomethylglaucine amide and N-feruloylphenylalanyl-3-aminomethylglaucine amide and their activity was due to the presence of hydroxycinnamoyl moiety in their molecules. The compounds were further tested in vitro for antiviral activity against viruses belonging to the Picornaviridae family. Furthermore, anti-tyrosinase activity of the compounds was performed in vitro. The results obtained suggested that the most promising tyrosinase inhibitor was feruloylphenylalanyl-3-aminomethylglaucine [ABSTRACT FROM AUTHOR]

Highlights: [•] Eight N-hydroxycinnamoylamides of fluorinated amino acids have been synthesized, among them five are new. [•] We evaluated their antioxidative activities by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test. [•] Among the tested amides, N-sinapoyl-3-fluorotyrosine methyl ester (5) exhibited the highest radical-scavenging activity. [•] SA-Trp(6-F)-OMe (4) inhibited the most significantly the formation of dopachrome in anti-tyrosinase assay. [ABSTRACT FROM AUTHOR]