Estudo químico das espécies Sabicea grisea Cham. & Schltdl. var. grisea e Psychotria barbiflora D. C (Rubiaceae) e avaliação das atividades antinociceptiva e anti-inflamatória de extratos e constituintes isolados

Abstract

This work describes the study chemical and pharmacological of the extracts and compounds isolated from two species of Rubiaceae (Sabicea grisea Cham. & Schltdl. var. grisea and Psychotria barbiflora DC.). Extracts and fractions of S. grisea, and fractions which showed positive reactions record to alkaloids of P. barbiflora, exhibited a significant reduction in the nociceptive response, with inhibition upper or comparable to the reference drug, indomethacin. The chemical study of fractions from leaves and stems of S. grisea, guided by pharmacological tests, resulted to the isolation of two saturated alcohols, octacosanol and hexacosanol, two pentacyclic triterpenes oleanane serie, siaresinolic and 3-O-α-L-rhamnopyranosyl-(1→2)-α-Larabinopyranosylsiaresinolic acids, vanillic and salicylic acids, scopoletin, ethyl caffeate and two phytosteroids, β-sitosterol and 3-O-β-D-glucopyranosylsitosterol. It is noteworthy that no previous reports about the presence of these compounds in the genus Sabicea. Moreover, no record was found on the 3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl-siaresinolic acid, named Gottliebside, an simple tribute to the greatest Natural Products Chemistry of the Brazil, Prof. Otto Richard Gottlieb, therefore, a new natural product. The chemical study of alkaloidal fractions from leaves and stems of P. barbiflora led to the isolation of two β-carboline alkaloids, harman and stricnosidinic acid, whose occurrences corroborate the inclusion of this species in the subgenus Heteropsychotria. In the pharmacological tests, octacosanol (10 and 1 mg/kg, i.p) and siaresinolic acid (1 and 0.1 mg/kg, i.p) showed peripheral antinociceptive effects mediated by α2-adrenergic receptors and channel K+ ATPdependent, respectively. Furthermore, these compounds inhibited the accumulation of inflammatory cells, as well as TNF-α in the model of carrageenan-induced inflammation, indicating an anti-inflammatory action. In addition, these compounds (≤200 μg/ml and ≤ 50 μg/ml, respectively) were unable to induce cell death in when evaluated in the reduction of 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test, demonstrating the absence of cytotoxicity of these compounds.