Temporal variation of chemical composition and relaxant action of the essential oil of Ocimum gratissimum L. (Labiatae) on guinea-pig ileum.

The medicinal plant Ocimum gratissimum L. (Labiatae) is widely encountered in the Northeast of Brasil where it is used to treat digestive problems. Its leaves have an essential oil (EOOG) content whose chemical composition varies according to the time of plant collection. We have compared the effects of the EOOG, collected at 08:00 a.m. (EOOG8) and at 12:00 a.m. (EOOG12), on the relaxation of guinea-pig isolated ileum. Both EOOG8 and EOOG12 (30-300 microg/ml) reversibly relaxed the spontaneous tonus of the guinea-pig ileum in a concentration-dependent manner, with similar IC50 values (49.3 and 23.8 microg/ml, respectively). The magnitude of the decrease in resting tonus was similar to that of the recognised smooth muscle relaxant papaverine. EOOG8 and EOOG12 relaxed 60 mM KCl-precontracted preparations similarly (38.33 +/- 9.91 microg/ml and 35.53 +/- 6.70), whereas a significantly more potent relaxant effect of EOOG12 compared to EOOG8 was observed when tissues were contracted using 10 microM acetylcholine (IC50 values of 69.55 +/- 4.93 and 128.16 +/- 15.70 microg/ml, respectively; p < 0.05). The principal constituents of the essential oil, eugenol and cineole, also relaxed KCl-precontracted preparations, although they were less potent than EOOG, suggesting that they alone were not responsible for EOOG-induced relaxations. Our results show that the essential oil extracted from the leaves of O. gratissimum L., collected at different time periods, exerts significant relaxant effects on isolated guinea-pig ileum which may underlie the therapeutic action of the plant.

Inhibitory effects of the essential oil of Mentha pulegium on the isolated rat myometrium.

The effects of the essential oil of Mentha pulegium L. (EOMP), a plant commonly known as "pennyroyal" or "poejo" that is used in folk medicine as an abortifaceant, were assessed on the isolated rat myometrium. Myometrial strips were stimulated with 10 nM oxytocin or 10 microM PGF (2alpha). EOMP (10 - 300 microg/mL) concentration-dependently and reversibly inhibited the amplitude of oscillatory contractions, being approximately 3-fold more active against contractions stimulated by oxytocin than those by PGF (2alpha) (IC (50) values of 45.7 +/- 5.6 microg/mL and 160.9 +/- 5.9 microg/mL , respectively), although the maximal inhibitory effect occurred at the same concentration (300 microg/mL ) in both cases. This action was shared by pulegone (30 - 300 microM), the principal component of the essential oil (IC (50) values of 21.8 +/- 2.1 microg/mL and 12.7 +/- 4.6 microg/mL , respectively). Nifedipine (30 nM - 30 microM) also abolished agonist-stimulated contractions, and was approximately twice and 12 times as potent as EOMP in inhibiting oxytocin- and prostaglandin F (2alpha) (PGF (2alpha))-stimulated contractions, respectively. In conclusion, our results show that the essential oil of the abortifaceant plant Mentha pulegium exerts an inhibitory effect on the contractile activity of the isolated rat myometrium. This oil shares a common effect with the voltage-dependent calcium channel (VDCC) blocker nifedipine, although ostensibly acting via a different mechanism. It thus appears that EOMP and pulegone do not exert direct toxic effects on the myometrium per se that would cause abortion, and other possibilities such as systemic metabolism of plant constituents may rather underlie the abusive use of Mentha pulegium in popular medicine.

Antinociceptive properties of the essential oil of Ocimum gratissimum L. (Labiatae) in mice.

We have investigated the antinociceptive effects of the essential oil of Ocimum gratissimum L. (Labiatae) (EOOG) in two classical models of pain in male Swiss mice (25-35 g), the writhing test and the formalin test. At doses of 30, 100 and 300 mg/kg (po), EOOG produced a dose-dependent inhibition (from 58.3 4.4 to 40.7 6.3, 36.4 3.6 and 24.6 3.6, respectively; N = 8-10, P<0.05) of acetic acid-induced writhing, causing up to a ~60% inhibition at the highest dose used, comparable to that obtained with indomethacin (10 mg/kg, po). At the same doses, EOOG predominantly inhibited the late (inflammatory) phase of the formalin-induced pain response (from 59.3 8.3 to 40.4 4.8, 23.2 2.8 and 25.3 5.5, respectively; N = 6, P<0.05), with a maximal reduction of ~60% of the control, although a significant reduction of the initial (neurogenic) phase was also observed at 300 mg/kg (from 62.5 6.07 to 37 5.9; P<0.05). On the basis of these data, we conclude that EOOG possesses interesting antinociceptive properties in the writhing and formalin tests. Due to the relatively low toxicity of EOOG, further detailed examination is strongly indicated for a better characterization of its pharmacological properties and its potential therapeutic value.

Bronchodilator activity of Mikania glomerata Sprengel on human bronchi and guinea-pig trachea.

The effects of aqueous extracts and hydro-alcoholic extract (HAE), and of a dichloromethane fraction (MG1) obtained from the HAE of Mikania glomerata leaves on isolated respiratory and vascular smooth muscle have been investigated. Aqueousextracts and HAE induced a significant inhibition on the histamine contractions on the isolated guinea-pig trachea. HAE extract induced a concentration-dependent relaxation on guinea-pig trachea pre-contracted with histamine (IC50 0.34 (0.29-0.39) mg mL(-1)), acetylcholine (IC50 0.72 (0.67-0.77) mg mL(-1)) or K+ (IC50 1.41 (1.18-1.64) mg mL(-1)) and on isolated human bronchi precontracted with K+ (IC50 0.34 (0.26-0.42) mg mL(-1)). The dichloromethane fraction induced a concentration dependent relaxation in guinea-pig trachea precontracted with K+ (IC50 0.017 (0.012-0.022) mg mL(-1)). The dichloromethane fraction had also a small vasodilator effect on the isolated mesenteric vascular bed and on the isolated rat aorta, and a significant reduction of the oedema induced by subplantar injections of Bothropsjararaca venom in mice. When tested on plasmid DNA, MG1 did not damage the DNA. Chromatographic analysis showed the presence of 11.4% w/w coumarin in MG1. The results supported the indication of M. glomerata products for the treatment of respiratory diseases where bronchoconstriction is present.

Myorelaxant and antispasmodic effects of the essential oil of Alpinia speciosa on rat ileum.

The effects of the essential oil of Alpinia speciosa Schum (EOAS) on rat ileum were studied. EOAS (0.1-600 microg/mL) reversibly relaxed ileal basal tonus. Submaximal contractions induced by 60 mM KCl or acetylcholine were concentration dependently inhibited by EOAS with similar IC(50) values ( approximately 44 and 48 microg/mL, respectively). These results show that EOAS possesses both relaxant and antispasmodic actions in the ileum.

Relaxant and antispasmodic actions of methyleugenol on guinea-pig isolated ileum.

The effects of methyleugenol (ME) on guinea-pig isolated ileum were studied. ME reversibly relaxed basal tonus (EC50 of 52.2 +/- 18.3 microM), an action unaltered by 0.5 microM tetrodotoxin or 0.5 mM hexamethonium, and relaxed the ileum pre-contracted with 60 mM KCl. ME slightly hyperpolarized the ileum from -57.3 to -62.8 mV but had no effect in depolarised tissues. ME inhibited contractions induced by ACh, histamine and KCl with IC50 values of approximately 82, 124, and 65 microM, respectively. Our results suggest that ME induces relaxation of guinea-pig ileum by a direct action on smooth muscle via a mechanism largely independent of alterations of membrane potential (Em).