Antihyperalgesic effects of an aqueous stem bark extract of Mangifera indica L.: role of mangiferin isolated from the extract.

This study aimed to assess the effects of a Mangifera indica stem bark extract (MSBE) and mangiferin (MG) on pain-related acute behaviors in the formalin 5% test. Rats received repeated oral MSBE (125-500 mg/kg) once daily for 7 days before formalin injection. Other four groups with the same treatments were performed in order to study the effect of MSBE on the formalin-induced long-term secondary mechano-hyperalgesia at 7 days after the injury by means of the pin-prick method. Additional groups received a single oral MSBE dose (250 mg/kg) plus ascorbic acid (1 mg/kg, i.p.). Also, repeated oral MG doses (12.5-50 mg/kg) during 7 days were administered. MSBE decreased licking/biting and flinching behaviors only in phase II and reduced the long-term formalin injury-induced secondary chronic mechano-hyperalgesia. The combination of MSBE plus ascorbic acid produced a reinforcement of this effect for flinching behavior, advising that antioxidant mechanisms are involved, at least in part, in these actions. Chronic administration of MG reproduced the effects of MSBE. For the first time, the antihyperalgesic effects of MSBE and MG in formalin 5% test, a recommended concentration for studying the antinociceptive activity of nitric oxide-related and N-methyl-d-aspartate-related compounds, were reported. These results could represent an important contribution to explain the analgesic ethnobotanical effects recognized to M. indica and other species containing MG.