Some observations on the antihistamine activity in the guinea pig of aliphatic 2,4-diketones, a new class of physiological tissue components.

Eight saturated aliphatic 2,4-diketones, ranging in chain length from C7 to C21 were examined for their potency in counteracting the effects of histamine anaphylaxis in guinea pigs. A 0.2% suspension of the mixed C15, C17, C19 and C21 diketones was more effective than a 1% phenylephrine solution when these were administered as aerosols. Of the individual diketones, 2,4-nonadecanedione was the most potent in vivo. ED50 data for the antihistamine activity of the C7, C9, and C13 homologues in the in vitro guinea pig ileum bioassay indicated that, on a weight basis, the activity increased with increasing molecular weight. The antiallergic activity of tissue and of urine extracts has been attributed to the presence of 2,4-diketones.