2-Styrylchromones were synthesized as vinylogues of 2-phenylchromones (flavones), a broad class of anti-rhinovirus compounds. The antiviral activity of 2-styrylchromones and 3-hydroxy-1-(2-hydroxyphenyl)-5-phenyl-2,4-pentadien-1-ones, which are intermediates in the synthesis, was evaluated against two selected serotypes of human rhinovirus, 1B and 14, by a plaque reduction assay in HeLa cell cultures. All of the compounds interfered with HRV 1B replication, with the exception of 3-hydroxy-1-(2-hydroxyphenyl)-5-(4-methoxyphenyl)-2,4-pentadien-1-one. The majority of derivatives were also found to be effective against serotype 14, often with a higher potency.

A series of homoisoflavonoids [(E)-3-benzylidenechroman-4-ones 1a-w, 3-benzyl-4H-chromen-4-ones 2a-g, and 3-benzylchroman-4-ones 3a-e] have been synthesized and tested in vitro as inhibitors of human monoamine oxidase isoforms A and B (hMAO-A and hMAO-B). Most of the compounds were found to be potent and selective MAO-B inhibitors. In general, the (E)-3-benzylidenechroman-4-ones 1a-w showed activities in the nano- or micromolar range coupled with high selectivity against hMAO-B. The reduction of the exocyclic double bond results in compounds 3a-e selective against isoform B and active in the micromolar range. In contrast, the endocyclic migration of the double bond (compounds 2a-g) generally produces the loss of the inhibitory activity or a marked reduction in potency. (E)-3-(4-(Dimethylamino)benzylidene)chroman-4-one (1l) and (E)-5,7-dihydroxy-3-(4-hydroxybenzylidene)chroman-4-one (1h) were the most interesting compounds of the entire series of inhibitors, showing hMAO-B affinity better than the selective inhibitor selegiline. Molecular modeling studies have been carried out to explain the selectivity of the most active homoisoflavonoids 1h and 1l.

Recently, we identified 2-styrylchromones as a new class of antirhinovirus flavonoids with moderate activity against both rhinovirus groups A and B. In order to improve the antiviral effect of the first series of tested 2-styrylchromones, a hydroxy or methoxy group was introduced in position 3 of the chromone ring. Cytotoxicity and antiviral activity of the new synthesized compounds were evaluated in HeLa cell cultures infected with rhinoviruses 1B and 14, selected as representative serotypes for viral groups B and A of human rhinoviruses (HRVs), respectively. These antiviral results compared to those obtained for 3-unsubstituted 2-styrylchromones indicate the greater potency of 3-hydroxy and 3-methoxy derivatives against both serotypes.

Fluoro-substituted flavones and 2-styrylchromones, related to natural and synthetic flavonoids previously described, were prepared, characterized and tested for anti-rhinovirus activity. Structural elucidation of the new compounds was performed by IR, NMR spectra and X-ray crystal structure analysis for 6-fluoro-3-hydroxy-2-styrylchromone. The antiviral potency was evaluated by a plaque reduction assay in HeLa cell cultures infected with rhinoviruses 1B and 14, selected as representative serotypes for viral groups B and A of human rhinoviruses, respectively. In comparison with results previously obtained, the introduction of the fluorine atom seems to exert a positive influence on the activity against serotype 14 while counteracting the effect against serotype 1B.

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