Pharmacological and toxicological study of a chemical-standardized ethanol extract of the branches and leaves from Eysenhardtia polystachya (Ortega) Sarg. (Fabaceae)

Eysenhardtia polystachya is used for the empirical treatment of cancer, infections, diarrhea, inflammation, and pain. This study identified, using GC-MS, the main chemical components in an ethanol extract of E. polystachya branches and leaves (EPE) and tested its cytotoxic, antimicrobial, anti-diarrheal, anti-inflammatory, and antinociceptive effects. The in vitro and in vivo toxicity of EPE was evaluated using the comet assay in human peripheral blood mononuclear cells (PBMC) and the acute toxicity test in mice, respectively. The cytotoxic and the antimicrobial effects were performed using the MTT assay and the minimum inhibitory concentration (MIC) test, respectively. The levels of pro-inflammatory mediators in LPS-stimulated macrophages were measured to evaluate the in vitro anti-inflammatory effects of EPE. The antidiarrheal (castor oil test, small intestine transit, and castor oil-induced enteropooling), and anti-inflammatory activities (TPA and carrageenan) of EPE were also performed. The antinociceptive actions of EPE were carried out with the following tests: acetic acid, formalin, and hot plate. The hypnotic and locomotor effects were analyzed using pentobarbital and a rotarod system, respectively. The main component in EPE was D-pinitol (26.93%). The antidiarrheal and antinociceptive effects of D-pinitol were also evaluated. EPE showed low in vitro toxicity (DNA damage in PBMC at concentrations higher than 200 µg/ml), and low in vivo toxicity (LD₅₀ > 2000 mg/kg i.p. and p.o.). Furthermore, EPE lacked cytotoxic activity (IC₅₀ > 300 µg/ml) on human cancer cells, but showed good antimicrobial effects in E. coli (MIC=1.56 µg/ml) and S. aureus (MIC = 0.78 µg/ml). In multi-drug resistant microorganisms, EPE showed MIC> 100 µg/ml. EPE exerted in vitro anti-inflammatory effects, mainly, by the decrease in the production of H₂O₂ (IC₅₀ = 43.9 ± 3.8 µg/ml), and IL-6 (73.3 ± 6.9 µg/ml). EPE (ED₅₀ =7.5 ± 0.9 mg/kg) and D-pinitol (ED₅₀ = 0.1 ± 0.03 mg/kg) showed antidiarrheal activity, and antinociceptive effects in the acetic acid test with ED₅₀ = 117 ± 14.5 mg/kg for EPE and 33 ± 3.2 mg/kg for D-pinitol. EPE showed also antinociceptive activity in the phase 2 of the formalin test (ED₅₀ = 48.9 ± 3.9 mg/kg), without inducing hypnotic effects or altering the locomotor activity in mice. The results here presented corroborate the folk medicinal use of Eysenhardtia polystachya in the treatment of infections, diarrhea, inflammation, and pain. D-pinitol, the main metabolite of EPE, showed antinociceptive and antidiarrheal effects with similar potency compared to standard drugs.