Antinociceptive activity of the ethanolic extract from Thai propolis

Abstract

Propolis (bee glue) is a resinous substance which contains a complex mixture of secondary metabolites, produced by honeybees. It has long been used in many countries for the management of several diseases. In these studies, we initially determined the analgesic property of a range of the ethanolic extract of Thai propolis (ETP) doses in the mouse hot-plate test. Hot-plate latencies (cut-off 45 sec) were determined in male ICR mice prior to the intraperitoneal (i.p.) administration of corn oil, 0.9% normal saline solution (NSS), morphine (MO: 10 mg/kg), indomethacin (IND: 150 mg/kg) or various doses of ETP (12.5, 25, 50, 100, 200, 400, 800 mg/kg). Hot-plate latencies were subsequently determined at 15, 30, 45, 60, 90, 120, 240 min. The percent maximum possible effect (%MPE) was calculated and used in determination of the area of analgesia (%MPE-min). ETP in doses of 50-800 mg/kg produced a significant dose-related analgesic response. ETP (200 mg/kg) produced analgesic response that was naloxone and naltrexone-sensitive suggesting opioid-mediated mechanism. In mouse tail-flick analgesia test, tail-flick latencies (cut-off 4 sec) were determined prior to the i.p. administration of corn oil, NSS, MO, IND or various doses of ETP (12.5-800 mg/kg) and were subsequently determined at 7 intervals over a 4-hr period. ETP in doses of 25-800 mg/kg produced a dose-dependent analgesic response. Studies then determined the analgesic effect of ETP using the formalin-induced nociception test. After the i.p. administration of corn oil, NSS, MO, IND or various doses of ETP (50-800 mg/kg), 2.5% solution of formalin was administered into subplantar area of the right hind paw. The number of licks were subsequently determined at the first 0–5 min, and the following 25–30 min after formalin administration. ETP dose of 200 mg/kg produced analgesic response during the first phase and ETP doses of 200 mg/kg or higher produced a significant dose-related analgesic response during the second phase. ETP doses of 200-800 mg/kg i.p. failed to produce motor impairment compared to vehicle control in the rota-rod test. Taken together these results demonstrate that the ethanolic extract of Thai propolis produced analgesic effect that was dose-dependent in all analgesic testing models without altering motor performance and mechanism of actions seem to be related to the opioid receptors.