Antinociceptive activity of ethanolic extract and isolated compounds of Urtica circularis

ETHNOPHARMACOLOGICAL RELEVANCE

Urtica circularis (Hicken) Sorarú is a medicinal plant commonly used in traditional medicine to relieve pain in inflammatory processes.

AIM OF THE STUDY

In the present study, the in vivo antinociceptive effect of Urtica circularis ethanolic extract and its isolated compounds has been investigated.

MATERIALS AND METHODS

Antinociceptive activity was evaluated through writhing, formalin and hot plate tests in mice. The phytochemical analysis was performed.

RESULTS

The extract produced significant inhibition on nociception induced by acetic acid (ED50: 72.2mg/kg, i.p.) and formalin (ED50: 15.8 mg/kg, i.p.) administered intraperitoneally and also orally. Atropine diminished the activity of the extract in the acetic acid test. In this model, at dose of 10mg/kg i.p., vitexin was the most active of the isolated compounds (inhibition of 91%), and chlorogenic acid, caffeic acid and vicenin-2 (6,8-di-C-glucosyl apigenin) produced an inhibition of 72%, 41% and 41%, respectively, whereas apigenin did not show any activity.

CONCLUSIONS

These results suggest that Urtica circularis extract produced antinociception possibly related to the presence of vitexin, chlorogenic, caffeic acid and vicenin-2. The activation of cholinergic systems seems to be involved in the mechanism of antinociception of the extract.

Antinociceptive activity of Eupatorium buniifolium aqueous extract

The antinociceptive properties of the aqueous extract of Eupatorium buniifolium aerial parts were investigated in chemical and thermal models of nociception in mice. Oral doses of 250 and 500 mg/kg produced an inhibition of 42.3% and 73.9%, respectively, of the abdominal writhes induced by acetic acid in mice. This antinociceptive effect was not reversed by pretreatment with naloxone. In the formalin test, the administration of 500 and 1000 mg/kg p.o. had no effects in the first phase (0-5 min) but produced a dose-dependent analgesic effect on the second phase (15-30 min) with inhibitions of the licking time of 38.9% and 57.3%, respectively. In the hot plate test, no effect was seen at the dose of 500 mg/kg p.o.

Antinociceptive and antiinflammatory activities of Artemisia copa extracts

The aqueous extract from aerial parts of Artemisia copa Phil. (Compositae), was evaluated for antinociceptive activity using writhing, formalin, and hot-plate tests in mice. A dose-related antinociceptive response was obtained in the writhing test at doses of 500 and 1000 mg/kg p.o. (percentage of inhibition 23.3 and 52.70, respectively). The extract also inhibited the second phase of formalin test (38.81%) and this effect was not antagonized by pretreatment with naloxone 5mg/kg i.p. Furthermore, no significant effect was obtained in the hot-plate test. Dichloromethane and ethanolic extracts, were analyzed for antiinflammatory activity with the carrageenan-induced paw edema in rats and the ear edema induced by 12-O-tetradecanoylphorbol-13 acetate (TPA) and arachidonic acid (AA) in mice. Both extracts showed antiinflammatory activity in the TPA (88 and 54%), and the ethanolic extract showed a 37% inhibition in AA test. No effects were seen at doses of 300 mg/kg p.o. and 100 mg/kg i.p. in the carrageenan test. The results obtained indicate that A. copa has analgesic and topical antiinflammatory activities that supports the folk medicinal use of the plant.

The hypoglycemic effect of Phyllanthus sellowianus fractions in streptozotocin-induced diabetic mice

Phyllanthus sellowianus Müller Arg. (Euphorbiaceae) is a plant used in folk medicine as a hypoglycemic and diuretic agent. The present study describes the hypoglycemic effect of fractions obtained from the stem barks of P. sellowianus using a bioassay-guided fractionation protocol and streptozotocin-induced hyperglycemic mice. The aqueous extract was partitioned between dichloromethane and butanol to yield the dichloromethane (D), butanol (B) and the remaining aqueous (A) fractions. Fractions B and A, administered at the dose of 200 mg/kg p.o., caused a significant reduction in blood glucose concentration at 6 and 9 h, while the same dose of fraction D was ineffective. The reduction in blood glucose levels obtained with the B and A fractions was similar to that observed with glibenclamide (10 mg/kg) which was used as a reference for the hypoglycemic activity. Phytochemical analysis of fractions B and A revealed the presence of flavonoid compounds, of which rutin and isoquercitrin were the major constituents, respectively. The possible involvement of these flavonoids in the hypoglycemic effect of the active fractions is discussed.

Antinociceptive effect of the aqueous extract of Balbisia calycina

The aqueous extract from the aerial parts of Balbisia calycina (Gris.) A.T. Hunziker et Ariza (Ledocarpaceae), was evaluated for antinociceptive activity using the abdominal constriction, hot plate and formalin tests. The extract was administered orally to male mice at doses of 200, 400 and 800 mg/kg. A dose-dependent antinociceptive effect of the extract was obtained with the abdominal constriction test at doses of 400 and 800 mg/kg. This antinociceptive effect was not reversed by pretreatment with naloxone. No significant response was obtained with the hot plate test. With the formalin test doses of 400 and 800 mg/kg had no significant effect during the first phase of the test (0-5 min), while with the dose of 800 mg/kg, a significant inhibition during the second phase (15-30 min) was observed. The phytochemical investigation of the aqueous extract of B. calycina revealed the presence of the flavonoids luteolin, avicularin and hyperoside. The possible involvement of these flavonoids (specially luteolin) in the antinociceptive action is discussed.

Hepatoprotective activity of Achyrocline satureioides(Lam) D. C

Aerial parts of Achyrocline satureioides(Lam) D. C. (Asteraceae) are used in folk medicine as infusions or decoctions for the management of several diseases including gastrointestinal and hepatic disorders. These data and the presence of flavonoids and caffeoyl derivatives have led us to study its hepatoprotective and choleretic activities. The hepatoprotective activity was evaluated in the bromobenzene- (BB-) induced hepatotoxicity model in mice through the measurement of the serum levels of alanine-aminotransferase (ALT) and aspartate transaminase (AST), thiobarbituric acid reacting substances (TBARS) and glutathione levels. The aqueous extract of the aerial parts of A. satureioides administered before BB, at the dose of 300 mg kg(-1)p.o., demonstrated significant inhibition (P< 0.01) in the BB increase of liver ALT and AST and in the BB-induced increase of liver TBARS content. Also it was able to significantly increase (P< 0.05) the depleted levels of liver glutathione. In addition, at the same dose, a significant increase (P< 0.01) in the bile flow of rats was found. The results obtained with the aqueous extract of A. satureioides support its use in popular medicine as a hepatoprotective and digestive agent, and the effects might be mediated through the antioxidant and choleretic activities.

Choleretic effect and intestinal propulsion of 'mate' (Ilex paraguariensis) and its substitutes or adulterants

'Mate' or 'Yerba mate' (Ilex paraguariensis, Aquifoliaceae) is a tonic and stimulant beverage widely used in South America. It is also traditionally used in gastrointestinal disorders as eupeptic and choleretic agent. Accordingly, the effect of decoctions of the leaves of I. paraguariensis and three of its substitutes or adulterants (Ilex brevicuspis, Ilex argentina and Ilex theezans) on bile flow (BF) and intestinal propulsion were investigated. I. paraguariensis and I. brevicuspis induced an increase in BF, while the latter also enhanced intestinal transit. In contrast, neither I. argentina nor I. theezans exerted any effect on BF or intestinal propulsion. These results suggest that the therapeutic properties of I. paraguariensis will be affected when at least an adulterant is present in the final commercial product of Yerba mate.

Antinociceptive effect of some Argentine medicinal species of Eupatorium

Eupatorium laevigatum, E. arnottianum and E. subhastatum, plants used in Argentine folk medicine for the treatment of inflammation and pain related problems, were evaluated for analgesic activity. The infusions of these species (500 mg/kg, p.o.) produced a reduction in the number of stretches of 46.6%, 41.5% and 35.6% respectively, in the acetic acid induced writhing test. This antinociceptive effect of the infusions was not reversed by pretreatment with naloxone. The infusions studied did not produce antinociceptive effects when assayed in the hot plate test. These results suggest that the analgesic activity is exerted by a mechanism unrelated to interaction with opioid systems.

Diuretic activity of an aqueous extract of Phyllanthus sellowianus

Phyllanthus sellowianus Muell. Arg. (Euphorbiaceae) is used widely as a hypoglycemic and diuretic agent in South American folk medicine. In order to assess the diuretic activity of this plant, test animals were treated with a single oral administration of an aqueous extract (5% w/v) of the stem bark of P. sellowianus (400 mg/kg body weight), which produced after 8 h a significant increase in the urinary excretion. In the studies on acute toxicity in mice neither mortality nor neurobehavioral or autonomic profile changes could be observed.

Pulsed electromagnetic fields in experimental cutaneous wound healing in rats

Electromagnetic fields are now being used in many diseases such as osseous, ligamental, cartilaginous, or nervous reparation, diabetes, and myocardial or cerebral ischemia. Although many publications show the usefulness of magneto-therapy, discrepancies exist about the utility of electromagnetic fields in skin wound healing. The objective of this work was to study the effect of pulsed electromagnetic fields on wound healing in rats. Twenty-two male Wistar rats were used; a circular lesion was made in the back of each animal. They were divided into three groups: group C (control) with sham treatment (n = 8), group NF, treated with topical nitrofurazone solution (n = 7), and group PEMF, treated with pulsed electromagnetic fields of 20 mT (n = 7). The treatments were 35 minutes twice a day. The absolute and relative values of the area and perimeter of the wounds showed significantly lower values in the PEMF group at days 7, 14, and 21 compared with those in group C (p < 0.01, analysis of variance), whereas the PEMF group showed significantly lower values at day 21 only compared with the NF group (p < 0.01, analysis of variance). The results suggest a significant beneficial stimulation in the wound healing process in rats treated with PEMF, which could lead to the development of a practical tool for research and clinical use.

Memory facilitation with posttrial injection of oxotremorine and physostigmine in mice

The immediate posttrial injection of oxotremorine (0.125, 0.250 and 0.500 muMol/kg i.p.) and equimolecular doses of physostigmine can facilitate the retention of a passive avoidance response in mice. Injections given 10 min after training also significantly facilitate retention, but injections given 30 or 120 min after training do not affect retention. These findings suggest an action of oxotremorine and physostigmine on mechanisms involved in memory storage. The enhanced retention produced by oxotremorine and physostigmine was blocked by pretreatment with atropine (2 muMol/kg, 20 min, i.p.) but was not affected by methylatropine (2 muMol/kg, 20 min, i.p.). The retention was not modified by posttrial injection of metoxotremorine (0.25 muMol/kg i.p.) or neostigmine (0.250 muMol/kg i.p.), quaternary analogs of oxotremorine and physostigmine, respectively. The results suggest a central action of both cholinergic agents attributable to an activation of muscarinic brain receptors.