Synthesis, antinociceptive activity and structure activity relationship of flavone derivatives.

Flavonoids are phenolic compounds that have always attracted pharmaceutical researchers and food manufacturers. Nature has indirectly provided us flavones in our daily diet i.e. tea, fruits, juices and vegetables. Flavones have got special position in research field of natural and synthetic organic chemistry due to their biological capabilities. Flavone derivative has been synthesized in good yield from ketone and corresponding aldehydes. The structures have been established by different spectroscopic techniques like 1H NMR, 13C NMR, IR and elemental analysis. The compounds were then screened for its acute toxicity and antinociceptive response in mice models with writhings induced by acetic acid, tail immersion and formalin-induced nociception assay procedures and structure activity relationship was established. The compounds were safe up to a maximum dose of 1200 mg/kg body weight in mice. The effects following pretreatment with naloxone were also studied to reveal the involvement of opioid receptors in the antinociceptive action. The flavone derivatives showed significant reduction in number of abdominal constrictions, increase in paw licking response time in both phases and a significant raise in latency time in nociception models. Moreover, the antinociceptive response was significantly attenuated by pretreatment with naloxone suggesting the involvement of opioid system in the antinociceptive action. The promising effects were shown by halogenated flavone. The flavone derivatives showed analgesic response in all models of nociception suggesting the involvement of opioid system in the antinociceptive action.