PHYTOTHERAPY RESEARCH, VOL. 10,655-658 (1996) zyxwvuts Studies on the Neuropharmacological Effects of zy Psidium guyanensis and Psidium pohlianum Essential Oils F. A. Santos and V. S. N. Rao* Department of Physiology and Pharmacology, Federal University of Cearil, PO Box 3157,60430-270, Fortaleza, CE, Brazil E. R. Silveira Department of Organic and Inorganic Chemistry, Federal University of Ceari. PO 12 200,60021, Fortaleza, CE, Brazil The essential oils extracted from the leaves of Psidium guyanensis Pers. and Psidium pohlianum Berg, were evaluated for their neuropharmacological effects. Both the oils zyxwv (400 mgkg, p.0.) in mice displayed potentiation of pentobarbital sleeping time and an increase of immobility time in the behavioural forced swimming test. Also at a similar dose, they reduced the mortality associated with amphetamine toxicity and zyxw pentylenetetrazol-induced convulsions. The Psidium essential oils demonstrated no influence on small intestinal secretion but caused significant inhibition of intestinal transit. No overt toxicity was observed in mice that received essential oils orally up to 4 gkg. The results suggest a probable depressant action of the essential oils of Psidium on central and peripheral nervous systems. Keywords: Psidium guyanensis; Psidium pohlianum; essential oils; neuropharmacological effects. INTRODUCTION The twigs or leaves of the genus zyxwvutsrq Psidium (Myrtaceae)plants have been traditionally used for the treatment of dysentery, pharyngitis and against intestinal colic (Nadkami, 1976; Vandenberg and Silva, 1988). In studies carried out with different extracts obtained from zyxwvut I? guajava, antimicrobial, antidiarrhoeal and narcotic properties were described (Aguiar et al., 1984; Lutterodt and Maleque, 1988; Lozoya er al., 1990). However, there were no reports on the pharmacologic data obtained with the essential oils from Psidium species. Recently, essential oils of two Psidium species, I? guyanensis and I? pohlianum were analysed for the volatile constituents (Andrade Net0 et al., 1994). Besides 1,8-cineole as the major constituent (40%-63%). a- pinene, Peudesmol and yeudesmol were found to be common compounds in both species. The present study reports the general toxicity and neuropharmacological activity of these two essential oils. MATERIALS AND METHODS Plant material and extraction. Fresh leaves of I? guyanensis Pers and I? pohlianum Berg, collected from Crato region (National Park of Araripe), CearA, Brazil was utilized for the study. Voucher specimen (#18505 l? pohlianum, #18645 I? guyanensis) are deposited in the Herbario Prisco Bezerra, Departamento de Biologia, Universidade Federal do CearA. The essential oils were obtained by steam distillation of the plant material in an all glass still apparatus. The yields were 0.56% and 1.32% respectively for I? pohlianum and l? guyanensis (Andrade Net0 ef al., 1994). zyxwvuts * Author to whom correspondenceshould be addressed. Animals and treatment. Male albino Swiss mice (20-25 g) maintained on a 12 h/12 h light-dark cycle at an ambient temperature of 24"+2"C with free access to standard laboratory food and tap water ad libitum were used for the experiments. The essential oils were suspended in 2% Tween 80 in distilled water and administered orally to overnight starved mice at doses of 100,200 and 400 mg/kg. Control animals were given vehicle only (10 mwkg) by the same route. Each experimental dose group consisted of a minimum of 6 animals. General behaviour and toxicity. The essential oils were administered orally to groups of mice in graded doses (50-4000 mgkg) and were observed for behavioural changes (Irwin, 1962) and for 24 h mortality. Amphetamine group toxicity. Mice were divided in groups of 10 and were treated with essential oils (400mg/kg) or vehicle orally 40 min before the injection of dexampheta- mine (20 mg/kg, i.p.). Mortality was recorded up to 24 h and the percentage protection afforded by essential oils was determined. Chlorpromazine (10 mgkg, p.0.) pretreated animals were included in the study for comparison (Bum and Hobbs, 1958). Pentobarbitone sleeping time. Groups of animals received pentobarbitone (40 mg/kg, i.p.) after 40 min of test essential oils or vehicle administration. The sleeping time was measured by observing the recovery of righting reflex. A chlorpromazine zyxw (5 mgkg, p.0.) pretreated group was included in the study for comparison (Dandiya and Collumbine, 1959). Analgesic activity. Analgesic activity was measured against chemical and thermal noxious stimuli. Acetic acid-induced writhing. The essential oils or vehicle CCC 095 1-418)(/96/080655-04 zyxwvutsrqp 0 1996 by John Wiley & Sons, Ltd. Accepted (revised) 23 March 1996