Evaluation of anti-inflammatory activity of hydroethanolic extract of Dilodendron bipinnatum Radlk

Ethnopharmacological relevance

Dilodendron bipinnatum Radlk. (Sapindaceae), popularly known as “mulher-pobre”, is a native tree of the Pantanal of Mato Grosso, Brazil. The stem bark of Dilodendron bipinnatum is used by the population, in the forms of decoction and maceration in the treatment of inflammatory conditions. There is no information in the literature demonstrating the anti-inflammatory activity of Dilodendron bipinnatum and its respective mechanism of action. This study aimed to evaluate the anti-inflammatory activity and mechanism of action of the hydroethanolic extract of the stem bark of Dilodendron bipinnatum (HEDb) using in vivo and in vitro experimental models.

Materials and methods

The stem bark of Dilodendron bipinnatum was macerated in 70% hydroethanolic solution (1:3, w/v) for 7 days, filtered, concentrated on a rotary evaporator and the residual solvent removed in oven at 40 °C, thus obtaining HEDb. Cytotoxicity of HEDb in RAW 264.7 was assessed by the Alamar blue assay. in vivo anti-inflammatory activity of HEDb was evaluated with carrageenan and dextran-induced paw edemas and lipopolysaccharide (LPS)-induced peritonitis in mice. Effects of HEDb on the inflammatory cytokines (TNF-α, IL-1β and IL-10) concentrations in the peritoneal fluid were evaluated using commercial ELISA kits. The in vitro anti-inflammatory activity was evaluated using RAW 264.7 cells stimulated with LPS and/or INF-γ, while a Griess method was employed to determine nitric oxide (NO) concentrations in the peritoneal lavage and in the supernatants of RAW 264.7 cells. Preliminary phytochemical analysis was carried out using classical methods and secondary metabolites detected on HEDb were analyzed and confirmed by high performance liquid chromatography (HPLC).

Results

HEDb showed very low cytotoxicity with IC₅₀>200±0.38 μg/mL. HEDb effectively inhibited paw edema by carrageenan in the 2nd hour at 20 mg/kg (36%, p<0.001), and by dextran in the 1st hour at 100 mg/kg (46%, p<0.01), after induction with the phlogistic agents. Furthermore, HEDb reduced total leukocytes and neutrophils migration at all doses tested producing maximum effect at 20 mg/kg (45% and 64%, p<0.001 respectively). HEDb also attenuated increases in the concentrations of the pro-inflammatory cytokines (IL-1β and TNF-α) and increased the level of the anti-inflammatory cytokine IL-10 in the peritonitis model. However, it had no effect on NO production in activated RAW 264.7 cells. Preliminary phytochemical analysis revealed the presence of phenolic compounds, chalcones, flavones, flavonones, flavonoids, saponins and coumarins. HPLC analyses identified some tannins, with epigallocatechin gallate being the major compound.

Conclusions

Our findings provide evidence for the popular use of the stem bark of Dilodendrum bipinnatum in inflammation. Its anti-inflammatory action was due, at least in part, to the inhibition of cell migration, of the inflammatory mediators and Th1 cytokines and an increase in Th2 cytokines, without affecting NO pathway. It can be suggested that tannins account at least in part for the anti-inflammatory activity of HEDb.