Tagetes lucida Cav. (Asteraceae) is an ancient medicinal plant commonly used to alleviate pain. Nevertheless, scientific studies validating this property are lacking in the literature. Animal models of pain were used to evaluate the antinociceptive and anti-inflammatory activities of T. lucida essential oil (TLEO) and a bioactive metabolite. The chemical constitution and possible toxicity of the extract and the mechanism of action of β-caryophyllene were also explored. Temporal course curves and dose–response graphics were generated using TLEO (0.1–10 mg/kg or 3.16–31.62 mg/kg) and β-caryophyllene (3.16–10 mg/kg). Metamizole (80 mg/kg) and indomethacin (20 mg/kg) were used as reference drugs in the formalin assay and writhing test in rats and mice, respectively. The β-caryophyllene mechanism of action was explored in the presence of naloxone (1 mg/kg), flumazenil (10 mg/kg), WAY100635 (0.16 mg/kg), or nitro-l-arginine methyl ester (L-NAME) (20 mg/kg) in the formalin test in rats. GC/MS analysis demonstrated the presence of geranyl acetate (49.89%), geraniol (7.92%), and β-caryophyllene (6.27%). Significant and dose-dependent antinociceptive response was produced by TLEO and β-caryophyllene without the presence of gastric damage. In conclusion, β-caryophyllene was confirmed as a bioactive compound in the T. lucida analgesic properties by involving the participation of receptors like opioids, benzodiazepines, and Serotonin 1A receptor (5-HT_1A), as well as nitric oxide.

Rutin is a bioflavonoid found in medicinal plants used to reduce anxiety. Evidence is lacking of rutin’s anxiolytic-like activity, putative mechanism(s) of action, and neural sites of effects. The basolateral amygdala (BLA) is the main brain region that regulates anxiety, through GABA_A/benzodiazepine (BDZ) receptors, which are modulated by flavonoids. Therefore, the main aim of this study was to investigate whether the anxiolytic-like effect of rutin involves GABA_A/BDZ receptors in the BLA. Rutin was administered systemically (30–1000 mg/kg, intraperitoneal) or microinjected into the BLA (16 nmol/4 µl, intracerebral), and its effects were assessed in the elevated plus-maze and open-field tests. Diazepam (1 mg/kg, intraperitoneal, or 7 nmol/4 µl, respectively) was used as a positive control. The mechanism of action was studied using flumazenil (BDZ antagonist, 5 mg/kg, intraperitoneal, or 7 nmol/4 µl, intracerebral) or picrotoxin (chloride channel GABA_A antagonist, 0.3 nmol/4 µl, intracerebral). Rutin, administered systemically or intra-amygdala, induced anxiolytic-like responses, similar to those of diazepam. The effect of diazepam was completely blocked by flumazenil, which also partly antagonized the effects of systemic rutin. By contrast, flumazenil exerted no effect and picrotoxin had only a partial action when rutin was infused in the BLA. These results suggest that the anxiolytic-like effect of rutin in the BLA involves GABAergic neurotransmission that is not associated with BDZ receptors.