Synthesis and pharmacological properties of naturally occurring prenylated and pyranochalcones as potent anti-inflammatory agents

An efficient approach has been developed for the synthesis of naturally occurring prenylated chalcones viz. kanzonol C (1), stipulin (2), crotaorixin (3), medicagenin (4), licoagrochalcone A (5) and abyssinone D (6) along with the pyranochalcones paratocarpin C (7), anthyllisone (8) and 3-O-methylabyssinone A (9). The key step of the synthesis is a Claisen-Schmidt condensation. Subsequently, their anti-inflammatory effects were investigated in lipopolysaccharides (LPSs)-induced RAW-264.7 macrophages. Of the synthesized chalcones, compounds 5 (IC₅₀=10.41 μmol/L), 6 (IC₅₀=9.65 μmol/L) and 8 (IC₅₀=15.34 μmol/L) show remarkable activity with no cytotoxicity. Compound 9 (IC₅₀=4.5 μmol/L) exhibits maximum (83.6%) nitric oxide (NO) inhibition, but shows slight cytotoxicity. The results reveal that the chalcones bearing the prenyl group at 3- and/or 5-position on ring A (acetophenonemoiety), i.e., 1-4 and 7 show weak, or no inhibition activity, whereas chalcones having the prenyl group only on ring B (aldehyde part), i.e., 5, 6 and 8 show significant activity on the production of inflammatory mediated NO with no cytotoxicity.