ABSTRACT
The antinociceptive effect of the methanolic extract (ME) and two triterpenes isolated from E. mosenii (Orchidaceae) has been investigated in chemical and thermal models of nociception in mice. The ME of E. mosenii (0.3-30 mg kg(-1), i.p. or 50-400 mg kg(-1), p.o.) produced dose-related, significant and long-lasting (4 to 6 h) inhibition of acetic acid-induced abdominal constriction, with ID50 values of 3.9 and 137.0 mg kg(-1), respectively. Pholidotin and 24-methylenecycloartenol isolated from E. mosenii (0.1-3.0 mg kg(-1), i.p.) also produced marked and dose-related inhibition of acetic acid-induced pain, with ID50 values of 0.9 and 1.1 mg kg(-1). However, these compounds and the ME were about 3- to 13-fold more potent at the level of ID50 than diclofenac when assessed in acetic acid-induced abdominal constriction. The ME of E. mosenii in the same range of doses produced dose-related inhibition of both phases of formalin-induced licking, with mean ID50 values for the first and the second phases of 0.9, 122.0 mg kg(-1) and 0.7, 258.0 mg kg(-1), respectively by i.p. or p.o. routes. In addition, the ME (0.3-30 mg kg(-1), i.p., or 50-400 mg kg(-1), p.o.) also caused dose-related inhibition of capsaicin-induced neurogenic pain with mean ID50 values of 5.2 and 130.0 mg kg(-1), respectively. Treatment of animals with naloxone (5 mg kg(-1), i.p.) completely reversed the antinociceptive effect caused by morphine (5 mg kg(-1), s.c.) and that caused by ME of E. mosenii (1 mg kg(-1), i.p.) when assessed against either phase of the formalin-induced pain. Furthermore, when assessed in the hot-plate test, ME (100 mg kg(-1), i.p.) and morphine (10 mg kg(-1), s.c.) caused significant increase in response latency. However, ME given daily for to 7 consecutive days did not develop tolerance to itself nor did it induce cross-tolerance to morphine. Taken together these data demonstrate that the ME of E. mosenii elicited pronounced antinociception, when assessed by i.p. or p.o. routes, against several models of pain. Its actions involve, at least in part, an interaction with opioid system, seeming no to be related with a non-specific peripheral or central depressant actions. Finally, the active principle(s) responsible for the antinociceptive action of E. mosenii is likely related to the presence of the triterpenes.
Subject(s)
Analgesics/pharmacology , Plant Extracts/pharmacology , Plants, Medicinal/chemistry , Triterpenes/pharmacology , Acetic Acid , Analgesics/isolation & purification , Animals , Capsaicin/pharmacology , Chromatography, Gas , Chromatography, Thin Layer , Dose-Response Relationship, Drug , Formaldehyde , Hot Temperature , Male , Methanol , Mice , Pain Measurement/drug effects , Phytosterols/pharmacology , Postural Balance/drug effects , Spectrophotometry, Infrared , Triterpenes/isolation & purificationSubject(s)
Analgesics, Non-Narcotic/isolation & purification , Plants, Medicinal/chemistry , Analgesics, Non-Narcotic/pharmacology , Animals , Brazil , Male , Mice , Pain Measurement/drug effects , Phytosterols/isolation & purification , Phytosterols/pharmacology , Plant Extracts/chemistry , Plant Extracts/pharmacology , Triterpenes/isolation & purification , Triterpenes/pharmacologyABSTRACT
Some phytoconstituents present in the R. Gardneriana Pl. Tr. leaves, a Brazilian medicinal plant, were isolated by column chromatography. Their preliminary analgesic effects were evaluated against formalin-induced pain in mice. The results demonstrated that four biflavonoids, identified as volkensiflavone, GB-2 a, fukugetin and fukugeside are the main active components of the ethyl acetate fraction. Such compounds exhibited significative analgesic activity in relation to the second phase (inflammatory pain) of the formalin test, suggesting that they are the compounds responsible for the pharmacological effects previously observed for the hydroalcoholic extract of this plant.
