Pharmacological Investigation on Sodium Salt and Acetyl Derivative of Anacardic Acid

Abstract

Abstract Sodium salts of anacardic acid (SA) and O ‐acetyl anacardic acid (AA) were subjected to pharmacological screening primarily on paradigms known to be affected by prostaglandin (PG) synthesis inhibitors. Results were compared with those elicited by known cyclo‐oxygenase inhibitors. SA and AA had little discernible effect on general behaviour and showed overt signs of central stimulation in unusually large doses. SA augmented spontaneous motor activity in mice and attenuated hexobarbitone hypnosis in rats. It augmented the convulsant action of pentylene‐tetrazol and inhibited the anticonvulsant effect of phenobarbitone against maximal electroshock‐induced seizures in rats. SA inhibited catalepsy induced by morphine and haloperidol in rats, and antagonized bradykinin‐induced catalepsy when administered intracerebroventricularly (i.c.v.) in rats. Both exhibited significant anti‐inflammatory activity against carrageenin‐induced acute inflammation in rats. This anti‐inflammatory effect was also in evidence when SA was administered i.c.v. SA and AA had no per se effect on rectal temperature in rats but significantly attenuated the hyperthermia induced by i.c.v. bradykinin or i.p. carrageenin. In all these parameters the effects of SA or AA were comparable to those elicited by diclofenac, aspirin or acetaminophen. However, unlike aspirin and diclofenac, which showed significant antinociceptive activity against phenylquinone‐induced writhing technique, SA was additionally effective against radiant heat and thermic stimulation‐induced nocisponsive technique. Both SA and AA appeared to be fairly safe drugs as assessed by acute toxicity studies. Like the cyclo‐oxygenase inhibitor, diclofenac, SA significantly reduced rat brain PGE 2 and PGF 2 α concentrations, as assessed by a radioimmunoassay technique. Pharmacological and biochemical studies indicate that anacardic acid functions as a PG synthesis inhibitor, with the added advantage of having a central analgesic property.