Antinociceptive Activity of Ent-Dihydrotucumanoic Acid Isolated from Gymnosperma glutinosum Spreng Less.

Preclinical Research The diterpene ent-dihydrotumanoic acid (DTA) was among the compounds isolated from Gymnosperma glutinosum (Spreng) Less (Asteraceae). There are no reports regarding the pharmacological effects of DTA. Cytotoxicity against cancer cells (1-250 µM), and the antibacterial (50-1400 µM) activity of DTA were evaluated using the MTT assay, and the minimum inhibitory concentration test, respectively. The antidiarrheal (1-100 mg/kg p.o.) and anti-inflammatory (2 mg/ear) effects of DTA were evaluated using castor oil and 12-O-tetradecanoylphorbol-13-acetate, respectively. The antinociceptive and sedative effects of DTA (1-100 mg/kg p.o.) were evaluated using two models of chemically-induced nociception, and the pentobarbital-induced sleeping time test, respectively. The antinociceptive mechanism of DTA was evaluated using the acetic acid writhing test with inhibitors related to pain processing pathways. The effects of DTA (10-100 mg/kg p.o.) on locomotor activity were evaluated using the rotarod test. DTA lacked cytotoxic activity (IC50  > 100 µM) on cancer cells, possessed moderate antibacterial effects against B. subtillis (MIC= 175 µM), moderate antidiarrheal and anti-inflammatory effects, and minimal vasorelaxant effects. In the formalin test, DTA showed antinociceptive effects in both phases. In the acetic acid test, DTA showed antinociceptive activity (ED50 = 50.2 ± 5.6 mg/kg) with potency similar to that of naproxen (NPX; ED50 =33.7 ± 4.5 mg/kg) an effect blocked by naloxone implicating an opioid mechanism. DTA also exerted antidiarrheal activity and showed no sedative effects or changes in locomotor activity in mice. Drug Dev Res 78 : 340-348, 2017. © 2017 Wiley Periodicals, Inc.