Anti-Inflammatory and Antinociceptive Potential of Hydroethanolic Extract of Bauhinia guianensis Aubl. in Zebrafish (Danio rerio)

The leaves and stems of Bauhinia guianensis Aubl. are used in traditional Amazonian phytotherapy for the treatment of pain and inflammation. This study investigates the anti-inflammatory and antinociceptive effects of hydroethanolic extracts from B. guianensis Aubl. leaves and stems (HELBg and HESBg, respectively) in vivo models of inflammation and hyperalgesia. Danio rerio experimental animals were submitted to the acute inflammation test, induced by intraperitoneal (ip.) administration of carrageenan 20 μg/animal (abdominal edema); the groups were previously treated orally with saline solution 2 μL/animal (SS), dimethyl sulfoxide 2 μL/animal (DMSO), indomethacin 10 mg/kg, HELBg 100 mg/kg and HESBg 100 mg/kg, n = 12 per experimental group to evaluate the inhibition of edema and alteration histopathology of the liver, intestine and kidney of these animals. The antinociceptive effect was observed from the body curvature index and the behavioral responses of Danio rerio, after an experimental protocol for the induction of hyperalgesia, by ip. administration of 10 μL/animal of 2.5% acetic acid; the animals were orally treated orally with saline solution 2 μL/animal (SS), dimethyl sulfoxide 2 μL/animal (DMSO), morphine 2.5 mg/kg, HELBg 100 mg/kg and HESBg 100 mg/kg, and n = 5 per experimental group. In carrageenan-induced edema, the group treated with HESBg inhibited edema formation over the 3 h of the experiment. Maximum edema was inhibited by 54% (p < 0.05) when compared to the control group. Both HELBg and HESBg prevented body curvature index changes (t(df=3,8) = 6.96 and t(df=3,8) = 6.61, respectively, both p < 0.0001). In the behavioral parameters sensitive to antinociceptive pharmacological modulation, due to the abdominal constriction induced by acetic acid, the administration of HELBg and HESBg resulted in an improvement in swimming activity, with the following results: increase in distance covered (F(df=3,16) = 6.50 and F(df=3,16) = 7.72, respectively, both p < 0.0001), decrease in freezing time (F(df=3,16) = 2.04 and F(df=3,16) = 1.28, respectively, both p < 0.0059), increase in the number of ascents to the upper area of the tank (F(df=3,16) = 33.02 and F(df=3,16) = 35.62, respectively, both p < 0.0009) and decreased time spent in that area (F(df=3,16) = 101.19 and F(df=3,16) = 103.59, respectively, both p < 0.0038). It is reasonable to suppose that both extracts modulated the variations induced by carrageenan and acetic acid through the inhibition of prostaglandin biosynthesis, thereby decreasing the release of inflammatory mediators, the sensitization of peripheral nociceptors, and, consequently, the perception of pain. These results suggest that HELBg and HESBg have anti-inflammatory and antinociceptive activities, likely of peripheral origin and associated with the inhibition of prostaglandin biosynthesis.