A New Β-Triketone and Antinociceptive Effect from the Essential Oil of the Leaves of Calyptranthes restingae Sobral (Myrtaceae)

Abstract

Calyptranthes restingae Sobral, known as "murta", is a species of the northeastern Brazilian used to treat fever, pain and inflammatory disorders. The essential oil from Calyptranthes restingae Sobral (Myrtaceae) collected in Sergipe, northeastern Brazil, was obtained through the hydrodistillation and its antinociceptive properties were evaluated. Chromatographic analysis revealed 14 components, but only five were identified, accounting for 98.50% of the oil: (E)-caryophyllene (2.40%), calyptrantone (81.03%), α-humulene (1.52%), β-selinene (8.54%), α-selinene (5.01%). The structure of the major compound, calyptrantone, was elucidated by 1 H and 13 C-NMR. This is the first time that a β-triketone has been identified in the essential oil of Calyptranthes genus and that calyptrantone has been reported as a natural product. This essential oil showed an antinociceptive effect in mice, reducing acetic-acidinduced abdominal writhing significantly in comparison with the control group (p<0.001), with the possible participation of opioids. In the formalin test, the oil also caused significant inhibition of licking time in both phases without loss of motor coordination. Besides, all doses of the oil decreased the leukocyte migration in peritoneal cavity induced by carrageenan (p<0.01). Together, these results indicate that the essential oil of C. restingae represents an important potential tool for management of neurogenic and inflammatory pain.