Antinociceptive activity of Pereskia sacharosa Griseb. (Cactaceae) and localization of bioactive compounds in mice brain

Background: Pereskia sacharosa Griseb is mainly distributed in the Bolivian Amazon. It is widely used to treat infections and pain in traditional medicine, such as headache, muscle pain, stomachache, and inflammation. Purpose: This study aimed to evaluate the antinociceptive activity of the leaf ethanolic extract and fractions of P. sacharosa that was obtained through micropropagation, possible mechanisms of action, and to identify the main bioactive compound by high liquid chromatography-mass spectrometry, as well as its localization in the brain of mice by means of histological analysis and epifluorescence. Methods: The fractions (C1F9 and C2F13) were isolated from the ethanolic extract of P. sacharosa leaves using open column chromatography. The antinociceptive activity of the ethanolic extract (10–100 mg kg⁻¹, intra peritoneal, i.p.) and fractions C1F9 and C2F13 (30 mg kg⁻¹, i.p.) were evaluated in a nociceptive pain model (formalin test) in mice. In addition, a possible mechanism of action was investigated by exploring some inhibitory receptors using naltrexone (NTX, a non-selective opioid receptor antagonist), flumazenil (FMZ, a benzodiazepine site antagonist in the Gamma-aminobutyric acid A [GABA_A] receptor), or WAY100635 (a 5-hydroxytryptamine 1A [5-HT_1A] serotonin 1A receptor antagonist). Results: Regarding the mechanism of action, only antinociceptive activity of treatments in the neurogenic phase of the formalin test was inhibited in the presence of the three explored antagonists. Furthermore, the presence of phenolic compounds was confirmed at the central nervous system (CNS) using their epifluorescence in coronal brain sections and histological analysis. Finally, acid hydrolysis of the ethanolic extract was performed, and it was shown that kaempferol is a product of acid hydrolysis confirmed with a posterior high liquid chromatography-mass spectrometry analysis. Conclusion: The leaves of P. sacharosa contain bioactive metabolites with antinociceptive activity, whereby epifluorescence was an optimum property to detect them at CNS. To the best of our knowledge, this is the first report that provides preclinical evidence of the medicinal use of this species in folk medicine for pain relief.