Oral treatment with Berberine reduces peripheral nociception: Possible interaction with different nociceptive pathways activated by different allogeneic substances.

ETHNOPHARMACOLOGICAL RELEVANCE: Berberine was identified in extracts of Berberis ruscifolia Lam., a plant used in traditional medicine as an analgesic. Its presence may be involved in the reported pharmacological activity of this species. However, there is still a lack of scientific research concerning its analgesic activity in the peripheral nervous system. AIM OF THE STUDY: To investigate Berb-induced antinociception in the formalin test and to evaluate several pathways related to its pharmacological antinociceptive effects in chemical models of nociception in mice. MATERIALS AND METHODS: The antinociceptive activity of Berb was assessed by inducing the paw licking in mice with different allodynic agents. In the formalin test, the antiedematous and antithermal effect of Berb was evaluated simultaneously in the same experiment. Other nociceptive behavior produced by endogenous [prostaglandin E2 (PGE2), histamine (His), glutamate (Glu) or bradykinin (BK)] or exogenous [capsaicin (Caps) and cinnamaldehyde (Cin)] chemical stimuli, and activators as protein kinase A (PKA) and C (PKC), were also evaluated.The in vivo doses for p.o. were 3 and 30 mg/kg. RESULTS: Berb, at 30 mg/kg p.o., showed a significant inhibition of the nociceptive action in formalin in both phases being stronger at the inflammatory phase (59 ± 9%) and more active than Asp (positive control) considering the doses evaluated. Moreover, Berb inhibited the edema (34 ± 10%), but not the temperature in the formalin test. Regarding the different nociceptive signaling pathways evaluated, the most relevant data were that the administration of p.o. of Berb, at 30 mg/kg, caused significant inhibition of nociception induced by endogenous [His (72 ± 11%), PGE2 (78 ± 4%), and BK (51 ± 7%)], exogenous [Cap (68 ± 4%) and Cinn (57 ± 5%)] compounds, and activators of the PKA [(FSK (86 ± 3%)] and PKC [(PMA(86 ± 6%)] signaling pathway. Berb did not inhibit the nociceptive effect produced by Glu. CONCLUSION: The present study demonstrated, for the first time, the potential of Berb in several nociceptive tests, with the compound present in B. ruscifolia contributing to the analgesic effect reported for this species.

Antinociceptive effect and identification of berberine alkaloid in Berberis ruscifolia extracts.

ETHNOPHARMACOLOGICAL RELEVANCE: Aerial parts (leaves and stems) of Berberis ruscifolia Lam. are a usual preparation as an analgesic, anti-inflammatory, antimalarial, antibacterial, and digestive in folk medicine. However, there were no previous studies of its chemical composition and biological activity related to analgesic effects. THE OBJECTIVE OF THE STUDY: The evaluation of the anti-nociception of the infusion (I), the decoction (D), and the ethanolic extract (EE) obtained from aerial parts of B. ruscifolia and its main chemical constituent in them, in mouse models. MATERIAL AND METHODS: The chemical constituent of B. ruscifolia extracts was evaluated and quantified by LC-MS and HPLC methodology. The inhibition of nociception in mice was analyzed by formalin and acetic acid-induced contortions tests. Also, when the formalin test was performed to evaluate the antinociceptive activity, the inhibition of edema formation and the antipyretic effect of each extract were simultaneously evaluated in the same experiment. For the oral administration in the in vivo assays, doses ranging from 10 to 1000 mg/kg and 10-30 mg/kg were used for extract and the chemical compound, respectively. RESULTS: The presence of berberine (Berb) was identified in the three evaluated extracts where the EE showed the highest content of this compound getting a yield of 2%, while in the I and D, Berb is present at 0.2%. The three extracts promoted a reduction of the contortions induced by acetic acid, being observed in EE the highest activity with 63 ± 6% of significant inhibition of the nociceptive behavior at a dose of 300 mg/kg, while D significantly inhibited 32 ± 12% at the same dose and for I at a dose of 1000 mg/kg an inhibition of 44 ± 8% was observed. Likewise, in the formalin trial, I and EE reduced nociception at a dose of 1000 (31 ± 5%) and 300 (35 ± 3%) mg/kg, respectively in the neurogenic phase, while in the second phase of the experiment, all the extracts evaluated showed an antinociceptive effect, with significant inhibition of I of 54 ± 6% and D of 44 ± 5% at a dose of 1000 mg/kg and for EE showed a 63 ± 2% inhibition at a dose of 300 mg/kg being the one with the highest antinociceptive activity. These extracts showed no inhibition in temperature and formalin-injected paw edema formation when compared to the control. As for Berb, at a 30 mg/kg dose, it showed significant inhibition of 70 ± 5% in the acetic acid-induced contortion test. CONCLUSION: Altogether, the present results evidenced the analgesic properties of B. ruscifolia, scientific information presented for the first time, and also provided important knowledge not reported so far about the chemical composition of its extracts, by identifying the presence of Berb in them. Finally, we were able to conclude that the analgesic effect demonstrated by this medicinal plant is partly due to the presence of Berb.

Involvement of the L-arginine-nitric oxide pathway in the antinociception caused by fruits of Prosopis strombulifera (Lam.) Benth.

ETHNOPHARMACOLOGICAL RELEVANCE: Prosopis strombulifera (Lam.) Benth. is a rhizomatous shrub that grows in the north and central zone of Argentina. In folk medicine, the fruits of this plant have been used as an astringent, anti-inflammatory and odontalgic agent and anti-diarrheic. AIM OF THE STUDY: To investigate the antinociceptive effect of ethanol (EE), chloroform (CE) and ethyl acetate (EtOAcE) extracts of Prosopis strombulifera fruits and the involvement of the l-arginine-nitric oxide pathway in this effect. MATERIALS AND METHODS: The antinociceptive effects of the EE, CE and EtOAcE of Prosopis strombulifera fruits were evaluated in vivo using the formalin-induced pain test in mice with aspirin and morphine as reference antinociceptive compounds. The participation of the l-arginine-nitric oxide pathway in the antinociceptive effect was investigated in the same animal model using l-arginine as a nitric oxide (NO) precursor. The in vitro inhibitory effect of the extracts on LPS-induced nitric oxide production and iNOS expression was investigated in a J774A.1 macrophage-derived cell line. RESULTS: CE (300mg/kg), in contrast to EE and EtOAcE, caused significant inhibition (p<0.05) of the in vivo nociceptive response. Moreover, CE (100-1000mg/kg, p.o.) produced a dose-dependent inhibition of the neurogenic and the inflammatory phases of the formalin test with inhibition values (at 600mg/kg) of 42±7% and 62±7%, respectively. CE inhibition was more potent in the inflammatory phase, with an ID(50) of 400.1 (252.2-634.8)mg/kg. The antinociception caused by CE (600mg/kg, p.o.) was significantly attenuated (p<0.05) by i.p. treatment of mice with l-arginine (600mg/kg). In addition, CE (100µg/mL) produced significant in vitro inhibition (p<0.001) of LPS-induced NO production, which was not observed with EE and EtOAcE at the same concentration. The inhibition of NO production by CE (10-100µg/mL) was dose-dependent, with an IC(50) of 39.8 (34.4-46.1)µg/mL, and CE significantly inhibited LPS-induced iNOS expression in J774A.1 cells. CONCLUSIONS: This study supports, in part, the ethnomedical use of Prosopis strombulifera fruits by showing that its CE produces moderate antinociception in vivo. The findings also provide scientific information for understanding the molecular mechanism involved in the analgesic effect of this plant.