Synthesis, stereochemical assignments, and biological activities of homoisoflavonoids.
A series of four naturally occurring homoisoflavonoids and eight analogs have been synthesized starting from an appropriately substituted phenol through chroman-4-one, in four steps. The products were assigned as E-isomers based on NMR spectroscopic data. The E-isomers were converted into Z-isomers by photoisomerization. The E- and Z-isomers showed distinct chemical shifts and the differences between (E) and (Z)-homoisoflavonoids in the proton NMR spectra afford a useful method for ascertaining the stereochemistry. The antioxidant activity of homoisoflavonoids was determined by superoxide (NBT) and DPPH free radical scavenging methods. The analog 7-hydroxy-3-[(3,4,5-trihydroxyphenyl)methylene]chroman-4-one displayed excellent activity followed by sappanone A in both the methods and were several times potent than the commercial antioxidants like BHA, BHT, etc. These compounds were evaluated in vitro for their inhibitory activities against 5-lipoxygenase (5-LOX) enzyme. The analog 7-hydroxy-3-[(N,N-dimethylaminophenyl)methylene]chroman-4-one was found to possess potent inhibitory activity and was comparable to that of the standard, nordihydroguiaretic acid. These results suggest that these homoisoflavonoids, with their potent antioxidant and 5-LOX inhibitory activities, may have useful applications as antioxidants and lead compounds for asthma and inflammatory diseases.
Siddaiah
Vidavalur
V
Department of Chemistry, Sri Venkatateswara University, Tirupati 517 502, India.
Rao
Chunduri Venkata
CV
Venkateswarlu
Somepalli
S
Krishnaraju
Alluri V
AV
Subbaraju
Gottumukkala V
GV
D000975:Antioxidants / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D005419:Flavonoids / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D016859:Lipoxygenase Inhibitors; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism
D000975:Antioxidants; D004791:Enzyme Inhibitors; D005419:Flavonoids; D016859:Lipoxygenase Inhibitors