Planta Med 2010; 76(13): 1419-1423
DOI: 10.1055/s-0029-1240942
Pharmacology
Original Papers
© Georg Thieme Verlag KG Stuttgart · New York

The Antinociceptive Effect of a Benzopyran (HP1) Isolated from Hypericum polyanthemum in Mice Hot-Plate Test is Blocked by Naloxone

Juliana Schulte Haas1 [*] , Alice Fialho Viana1 [*] , Ana Paula Machado Heckler1 , Gilsane Lino von Poser1 , Stela Maris Kuze Rates1
  • 1Programa de Pós-graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
Further Information

Publication History

received October 8, 2009 revised Dec. 23, 2009

accepted February 3, 2010

Publication Date:
22 March 2010 (online)

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Abstract

Several species of the genus Hypericum (Guttiferae) have been used for analgesic purposes all over the world and some of them have demonstrated to possess this effect in rodents. This study describes the antinociceptive effect of the cyclohexane extract from aerial parts of H. polyanthemum (POL) as well as of benzopyrans, 6-isobutyryl-5,7-dimethoxy-2,2-dimethyl-benzopyran (HP1), 7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethyl-benzopyran (HP2), and 5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethyl-benzopyran (HP3), which are the main components of POL. The antinociceptive effect was evaluated through hot-plate and writhing tests in mice, and the opioid system involvement was assessed by using naloxone (2.5 mg/kg, s. c.) antagonism. In the hot-plate test, POL (45, 90, 180 mg/kg, p.o) showed a dose-dependent effect, and out of the benzopyrans only HP1 (30, 60, 90 mg/kg, i. p.) was active. Its effect was also dose-dependent, with the maximum reached at 60 mg/kg. HP1 60 mg/kg (p. o.) also inhibited acetic acid-induced writhing in 58 %. The pretreatment with naloxone abolished the antinociceptive effect of HP1 60 mg/kg (i.p) in the hot plate. Furthermore, the H. polyanthemum cyclohexane extract and HP1 did not affect the mice performance in the rota-rod apparatus suggesting that at antinociceptive doses they do not present gross neurotoxicity nor induce motor impairment. From these data it is reasonable to assume that the benzopyran HP1 accounts for the H. polyanthemum cyclohexane extract antinociceptive effect, and this effect is, at least in part, mediated by an opioid-like mechanism.

References

1 These authors have contributed equally to the studies presented in this manuscript.

Prof. Dr. Stela Maris Kuze Rates

Programa de Pós-graduação em Ciências Farmacêuticas
Universidade Federal do Rio Grande do Sul

Av. Ipiranga 2752

Porto Alegre, RS 90610–000

Brazil

Phone: + 55 51 33 08 54 55

Fax: + 55 51 33 08 54 37

Email: stela.rates@ufrgs.br