O Ácido (8)17,12E,14-labdatrieno-18-óico (labdano302), diterpeno tipo labdano isolado de Xylopia langsdorffiana St. Hil. & Tul. (Annonaceae) relaxa a traquéia isolada de cobaia

Abstract

"The (8)17,12E,14-labdatrien-18-oic acid (Iabdane302), labdane-type diterpene isolated from Xylopia langsdorffiana St. Hil. & Tul. (Annonaceae) relaxes the guinea-pig trachea". Xylopia langsdorfiana St. Hil. & Tul. is popularly known as "pimenteira-da-terra" in Southeast of Brazil. The fractionation of the ethanol extract obtained from the stem-bark of this species yielded a labdane-type diterpene identified as 8(17),12E,14-labdatrien- 18-oic acid, referred here as labdane302. In this study, we investigated the effect of labdane302 in guinea-pig trachea. labdane302 relaxed the basal tonus of trachea rings with EC50 value of 6.7 ± 0.5 × 10 -8 M. The diterpene labdane302 relaxed the pre-contracted rings by carbachol 10-6 M both in the presence (EC50 = 1.4 ± 0.7 × 10-5M) and absence of functional epithelium (EC 50 = 1.5 ±0.3 × 10-5M), as well as pre-contracted by KCl 18 mM or 60 mM, presented EC50 values of 2.3 ± 0.4 × 10-7 M and 1.8 ± 0.8 × 10 -5 M, respectively. This relaxant effect, upon contractions induced by KCl 18 mM, was more potent as well as more efficient than the one presented with KCl 60 mM pre-contracted rings. The labdane-type diterpene labdane302 shows the relaxant effect in isolated guinea-pig trachea, pre-contracted or upon basal tonus, apparently without participation of epithelium-derived relaxant factors, but apparently involving activation of K+ channels.