Antinociceptive effect of LMH-2, a new sigma-1 receptor antagonist analog of haloperidol, on the neuropathic pain of diabetic mice.

This study evaluates the antiallodynic and antihyperalgesic effects of LMH-2, a new haloperidol (HAL) analog that acts as sigma-1 receptor (σ1 R) antagonist, in diabetic mice using a model of neuropathic pain induced by chronic hyperglycemia. Additionally, we compared its effects with those of HAL. Hyperglycemia was induced in mice by nicotinamide-streptozotocin administration (NA-STZ, 50-130 mg/kg). Four weeks later, mechanical allodynia was assessed using the up-down method, and hyperalgesia was evoked with formalin 0.5%. We evaluated antiallodynic and antihyperalgesic effects of LMH-2 (5.6-56.2 mg/kg), HAL (0.018-0.18 mg/kg) and gabapentin (GBP, 5.6-56.2 mg/kg). The results showed that LMH-2 had a more significant antiallodynic effect compared to HAL and GBP (90.4±8.7 vs 75.1±3.1 and 41.9±2.3%, respectively; P<0.05), as well as an antihyperalgesic effect (96.3±1.2 vs 86.9±7.41 and 86.9±4.8%, respectively; P<0.05). Moreover, the antiallodynic and antihyperalgesic effect of both LMH-2 and HAL were completely abolished by PRE-084 (σ1 R agonist); and partially by pramipexole (a D2-like receptor agonist). Finally, the effect of all treatments on the rotarod test, barra, open field and exploratory behaviors showed that LMH-2 did not alter the animals' balance or the exploratory behavior, unlike as HAL or GBP. The molecular docking included indicate that LMH-2 has lower affinity to the D2R than HAL. These results provide evidence that LMH-2 exerts its antinociceptive effects as a σ1 R antagonist without the adverse effects induced by HAL or GBP. Consequently, LMH-2 can be considered a good and safe strategy for treating neuropathic pain caused by hyperglycemia in patients with diabetes.

Clavulanic Acid and its Potential Therapeutic Effects on the Central Nervous System.

Clavulanic acid (CLAV) is a non-antibiotic ß-lactam that has been used since the late 1970s as a ß-lactamase inhibitor in combination with amoxicillin, another ß-lactam with antibiotic activity. Its long-observed adverse reaction profile allows it to say that CLAV is a well-tolerated drug with mainly mild adverse reactions. Interestingly, in 2005, it was discovered that ß-lactams enhance the astrocytic expression of GLT-1, a glutamate transporter essential for maintaining synaptic glutamate homeostasis involved in several pathologies of the central nervous system (CNS). This finding, along with a favorable pharmacokinetic profile, prompted the appearance of several studies that intended to evaluate the effect of CLAV in preclinical disease models. Studies have revealed that CLAV can increase GLT-1 expression in the nucleus accumbens (NAcc), medial prefrontal cortex (PFC), and spinal cord of rodents, to affect glutamate and dopaminergic neurotransmission, and exert an anti-inflammatory effect by modulating the levels of the cytokines TNF-α and interleukin 10 (IL-10). CLAV has been tested with positive results in preclinical models of epilepsy, addiction, stroke, neuropathic and inflammatory pain, dementia, Parkinson's disease, and sexual and anxiety behavior. These properties make CLAV a potential therapeutic drug if repurposed. Therefore, this review aims to gather information on CLAV's effect on preclinical neurological disease models and to give some perspectives on its potential therapeutic use in some diseases of the CNS.

Antinociceptive and antiedema effects produced in rats by Brassica oleracea var. italica sprouts involving sulforaphane.

Natural products are recognized as potential analgesics since many of them are part of modern medicine to relieve pain without serious adverse effects. The aim of this study was to investigate the antinociceptive and anti-inflammatory activities of an aqueous extract of Brassica oleracea var. italica sprouts (AEBS) and one of its main reported bioactive metabolites sulforaphane (SFN). Antinociceptive activity of the AEBS (30, 100, and 300 mg/kg, i.p. or 1000 and 2000 mg/kg, p.o.) and SFN (0.1 mg/kg, i.p.) was evaluated in the plantar test in rats to reinforce its analgesic-like activity at central level using the reference drug tramadol (TR, 50 mg/kg, i.p.). The anti-inflammatory-like response was determined in the carrageenan-induced oedema at the same dosages for comparison with ketorolac (KET, 20 mg/kg, i.p.) or indomethacin (INDO, 20 mg/kg, p.o.). A histological analysis of the swollen paw was included to complement the anti-inflammatory response. Additionally, acute toxicity observed in clinical analgesics as the most common adverse effects, such as sedation and/or gastric damage, was also explored. As a result, central and peripheral action of the AEBS was confirmed using enteral and parenteral administration, in which significant reduction of the nociceptive and inflammatory responses resembled the effects of TR, KET, or INDO, respectively, involving the presence of SFN. No adverse or toxic effects were observed in the presence of the AEBS or SFN. In conclusion, this study supports that Brassica oleracea var. italica sprouts are a potential source of antinociceptive natural products such as SFN for therapy of pain alone and associated to an inflammation condition.

Antinociceptive effect of Mansoa alliacea polar extracts involves opioid receptors and nitric oxide in experimental nociception in mice.

To evaluate the antinociceptive effect and the possible mechanism of action of two polar extracts of Mansoa alliacea, a medicinal plant used in Perú, Brazil, and Mexico to treat rheumatic pain, we used the formalin and hot-plate tests in mice. We found that ethanolic (MA-EtOH) and aqueous (MA-AQ) extracts of M. alliacea induced antinociceptive effects in both nociceptive tests. The antinociceptive efficacy of the highest dosage (300 mg/kg) of both extracts were also compared by using intraperitoneal and oral administration in the formalin test. Results showed that intraperitoneal injection of the two extracts produced better antinociceptive effects than that obtained by their oral administration. The mechanism of action involved in their antinociceptive activity was determined in the formalin test. Results showed that the presence of A784168 (TRPV1 antagonist) did not alter the antinociceptive effect induced by any of the M. alliacea extracts, whereas naltrexone (opioid antagonist) partially prevented the antinociceptive effect only of MA-EtOH in both phases of the formalin test. Furthermore, the effects of the extracts were diminished by L-NAME (inhibitor of nitric oxide synthase), but not by ODQ (inhibitor of the soluble guanylyl cyclase) or glibenclamide (blocker of K+ATP channels) in the neurogenic phase. However, the effect of MA-AQ was diminished by all the inhibitors in the inflammatory phase. These results support the use of M. alliacea as a potential natural product with efficacy for pain relief depending on the form of preparation and the route of administration by involving opioid receptors and the production of nitric oxide.

Synergistic Herb-Herb Interaction of the Antinociceptive and Anti-Inflammatory Effects of Syzygium aromaticum and Rosmarinus officinalis Combination.

The use of alternative medicine to treat pain has been increased, and the combination of several medicinal plants for its relief is a common practice in traditional medicine. The present study is aimed at determining whether a combination of Syzygium aromaticum (S. aromaticum) and Rosmarinus officinalis L. (R. officinalis) potentiates their antinociceptive and anti-inflammatory effects. These effects were explored using the formalin and carrageenan assays in rats, respectively. Animals received local pretreatment with S. aromaticum oil or R. officinalis ethanolic extract (0.1-100 µg/paw) alone or combined in a 1 : 1 rate. Concentration-response curves were built to compare pharmacological responses after an individual administration of S. aromaticum, R. officinalis, or their combination. The pharmacological interaction was investigated by an isobolographic study using the EC50 of each component in a fixed 1 : 1 ratio. S. aromaticum and R. officinalis administered alone showed significant and concentration-dependent antinociceptive and anti-inflammatory effects, but R. officinalis was more potent than S. aromaticum in both the antinociceptive and anti-inflammatory effects (EC50 = 7.96 ± 0.6 µg/paw vs. EC50 = 41.6 ± 1.7 µg/paw; EC50 = 1.97 ± 0.3 µg/paw vs. EC50 = 26.9 ± 2.5 µg/paw, respectively). The isobolographic analysis of the combination of these species in a 1 : 1 ratio showed a synergistic interaction between S. aromaticum and R. officinalis since Z mix (experimental value) was lower than Z add (theoretical value) for both the antinociceptive effect (Z mix = 0.45 ± 0.1 < Z add = 24.8 ± 1.3) and the anti-inflammatory effect (Z mix = 5.2 ± 0.6 < Z add = 14.4 ± 2.2), suggesting a potentiation for both pharmacological effects. These results prove evidence of the efficacy of mixture herb-herb used in folk medicine for pain therapy. It also emphasizes the requirement of pharmacological studies to explore the efficacy and safety of herb interactions.

Quercetin decreases the antinociceptive effect of diclofenac in an arthritic gout-pain model in rats.

OBJECTIVE: To analyse the antinociceptive interaction between quercetin (QUER) and diclofenac (DIC) in experimental arthritic gout-pain. METHODS: The antinociceptive effect of DIC and QUER alone and in combination were evaluated using an arthritic gout-pain model. Pain was induced through intra-articular administration of uric acid in the rats and the treatments were administered 2 h later. Additionally, the cyclooxygenase (COX) activity was determined in rats treated with DIC, QUER and their combination. KEY FINDINGS: DIC induced a maximal effect of 69.7 ± 2.7% with 3.1 mg/kg; whereas QUER only produced 17.6 ± 2.6% with the maximal dose (316 mg/kg). Ten of twelve DIC + QUER combinations showed a lesser antinociceptive effect than DIC alone did (P < 0.05). Moreover, DIC reduced total-COX (70.4 ± 1.3 versus 52.4 ± 1.8 and 77.4 ± 9.0 versus 56.1 ± 1.3, P < 0.05) and COX-2 (60.1 ± 1.0 versus 42.4 ± 1.8 and 58.1 ± 2.4 versus 48.7 ± 1.3, P < 0.05) activity after 1 and 3 h, respectively. Nevertheless, only the COX-2 activity induced by DIC was prevented in the presence of QUER (63.2 ± 3.0 versus 60.1 ± 1.0 and 56.6 ± 1.3 versus 58.1 ± 2.4 at 1 and 3 h, respectively). CONCLUSIONS: All these data demonstrated that the simultaneous administration of QUER + DIC produces an unfavorable interaction on the antinociceptive effect of DIC. Therefore, this combination might not be recommendable to relieve arthritic gout-pain.

Antinociceptive Synergy Between Metamizole and Hesperidin in a Model of Visceral Pain in Mice.

BACKGROUND: Metamizole is used to relieve the visceral pain but its adverse effects limit its use. An alternative to improve its efficacy with lower doses is to combine it with a natural product as hesperidin. AIM OF THE STUDY: The aim of this study was to evaluate the antinociceptive interaction between metamizole and hesperidin in a visceral pain model using an isobolographic analysis. METHODS: Antinociception was evaluated in the writhing model using acetic acid (1%) to induce writhes in mice. Metamizole (1-316 mg/kg), hesperidin (3-300 mg/kg), or combinations with a fixed-dose ratio of 1:1 were administered intraperitoneally 30 min before the acetic acid and the number of writhes was counted for 30 min. Isobolographic analysis was employed to define the nature of the compound interaction. RESULTS: Metamizole and hesperidin in individual administration induced dose-dependent antinociceptive effects, reached an efficacy of 84.2 ± 5.9% and 66.3 ± 7.4%, respectively. The ED50 values calculated from their dose-response curves were 84.5 ± 22.7 and 108.9 ± 17.9 mg/kg, respectively. The analysis of DRC for the metamizole + hesperidin combination, in a ratio 1:1 showed a ED50 COMB value lower than the ED50 ADD estimated from the additivity line from the isobologram (46.7 ± 6.3 vs. 96.7 ± 11.9 mg/kg, respectively). In addition, the pharmacological interaction calculated was of 0.48. These results suggest a synergistic interaction for the antinociceptive activity of metamizole + hesperidin combination. CONCLUSION: These data suggest that metamizole + hesperidin combination could be useful in treating visceral pain as it can interact synergistically using low dose of both drugs with the possibility of reducing the risk of adverse effects.

Gastrointestinal activity of Justicia spicigera Schltdl. in experimental models.

Justicia spicigera Schltdl. (Acanthaceae) is used for treatment of gastrointestinal illnesses therapy in traditional medicine. The objective of this study was to give evidence of the antinociceptive and spasmolytic effects of the J. spicigera ethanol extract (JS EtOH) using in in vivo and/or in vitro assays. The JS EtOH exerted regulatory effect on the motility and a partial relaxing response on the intestinal tissue. Furthermore, a significant abdominal antinociceptive response was obtained in mice, which was totally abolished in the presence of 5-HT1A receptor antagonist (WAY100635, 0.1 mg/kg, s.c.) and partially by blocking opioid receptors (NX, 1 mg/kg, i.p.), whereas the inhibition of the NO synthesis (L-NAME, 30 mg/kg, i.p.) facilitated antinociception of this extract. Kaempferitrin was isolated and identified as major secondary metabolite. These results support the analgesic and spasmolytic-like activity of J. spicigera aerial parts involving inhibitory neurotransmission reinforcing the potential of this medicinal plant for alleviating pain.

Study of Antispasmodic and Antidiarrheal Activities of Tagetes lucida (Mexican Tarragon) in Experimental Models and Its Mechanism of Action.

Tagetes lucida has been used in traditional medicine as a remedy to alleviate several gastrointestinal disorders that provoke stomachaches, abdominal cramps, and diarrhea. However, there is not enough scientific evidence that supports these effects. Therefore, the purpose of this study was to evaluate antispasmodic and antidiarrheal activities of aqueous extract of T. lucida (AqExt-TL) as well as its mechanism of action in experimental models. Antispasmodic activity and the mechanism of action of AqExt-TL were assessed on segments of the guinea pig ileum precontracted with KCl, acetylcholine (ACh), or electrical field stimulation (EFS). Furthermore, the antispasmodic effect of two coumarins (umbelliferone and herniarin) previously identified in this species was evaluated. Antidiarrheal activity of AqExt-TL was determined using the charcoal meal test in mice. AqExt-TL showed antispasmodic activity in segments of the guinea pig ileum precontracted with KCl (83.7 ± 1.9%) and ACh (77.2 ± 5.3%) at the maximal concentration; however, practically, it did not alter the contractions induced by EFS (10.1 ± 2.2%). Antispasmodic activity of AqExt-TL was not significantly altered by hexamethonium (a ganglionic blocker) or L-NAME (an inhibitor of nitric oxide synthase). However, this extract decreased the maximal contractile response to calcium (82.7 ± 8.5%), serotonin (68.1 ± 8.5%), and histamine (63.9 ± 5.9%) in their concentration-response curves. Umbelliferone and herniarin also induced an antispasmodic effect on tissues precontracted with KCl. In addition, low doses of AqExt-TL reduced to 50% the distance traveled by charcoal meal in the gastrointestinal transit model in mice as loperamide, an antidiarrheal agent, did. These results provided evidence of the antispasmodic and antidiarrheal activity of T. lucida, which supports its use in the folk medicine in relieving symptoms in some gastrointestinal disorders. In the antispasmodic effect, the blockade of histaminergic and serotoninergic pathway as well as the calcium channels seems to be involved. Finally, umbelliferone and herniarin could be partially responsible for the antispasmodic activity induced by T. lucida.

Spasmolytic effect of aqueous extract of Tagetes erecta L. flowers is mediated through calcium channel blockade on the guinea-pig ileum.

This study provides pharmacological evidence on the spasmolytic activity of Tagetes erecta L. (marigold or cempasúchil) on the guinea-pig ileum and presents data on its mechanism of action. The relaxant effect on KCl contractions was more marked with aqueous (AqEx) than with ethanol extracts (EtEx) of T. erecta flowers (55.6 ±â€¯11.0 vs 21.1 ±â€¯4.4%, respectively). In addition, the aqueous extract antagonized contractions elicited by EFS, but not by acetylcholine (73.5 ±â€¯1.9 vs 14.5 ±â€¯5.3%, respectively). These effects were not diminished by hexamethonium or L-NAME, but this extract caused a rightward shift in the Ca2+ concentration-response curves like that of verapamil. Quercetin and rutin, two flavonoids present in this plant, also showed spasmolytic effects (95.7 ±â€¯2.8 and 27.9 ±â€¯7.1%, respectively). Interestingly, in tissues without spasmogens, the extract induced contractions superimposed on their spontaneous activity. These results support the traditional use of T. erecta as a spasmolytic in folk medicine and suggest mainly that quercetin could be partly responsible for this effect. The spasmolytic effect appears to involve voltage-gated calcium channels, but not the nitric oxide pathway or the release of neurotransmitters from enteric neurons. Nevertheless, this plant could produce colic or stomachache as adverse effects in clinical situations in which these symptoms are not originally present.

Preclinical evidence of the anxiolytic and sedative-like activities of Tagetes erecta L. reinforces its ethnobotanical approach.

Morelos State is one of the regions of Mexico where several plant species are used in traditional medicine. Species from Tagetes genus (Asteraceae) are reported as useful in infusion to treat stomachache and intestinal diseases, but also as tranquilizers. In this study, medicinal uses of T. erecta including its depressant effect on the central nervous system (CNS) were explored by interviewing healers and merchants of local markets of Morelos State, and by investigation of the phytochemical and pharmacological tranquilizing properties. Specific anxiolytic and/or sedative-like responses of different doses of T. erecta (10, 30 and 100 or 300mg/kg, i.p.) were investigated using experimental models in mice such as: open-field, exploration cylinder, hole-board, and the barbituric-induced hypnosis potentiation. The possible anxiolytic mechanism of action was assessed in the presence of WAY100635 (0.32mg/kg, i.p.) and flumazenil (10mg/kg, i.p.), antagonists of 5-HT1A and GABA/BDZs receptors, respectively. Individual flavonoids reported in this species were also evaluated in these experimental models. As a result of this study, healers and merchants from ten local regions of Morelos State recommended T. erecta flowers as an infusion or as a tincture for several culture-bound syndromes associated with CNS, among others. Anxiolytic and sedative-like activities of the T. erecta aqueous and organic polar extracts were corroborated in these models associated to a participation of rutin, kaempferol, quercetin, kaempferitrin, and ß-sitosterol constituents; where 5-HT1A, but not BDZs, receptors were involved as anxiolytic mechanism of action. These data support the anxiolytic and sedative-like properties of T. erecta in traditional medicine by involving mainly serotonergic neurotransmission because of the presence in part of flavonoids and the terpenoid ß-sitosterol.

Spasmolytic Action of Preparations and Compounds from Hofmeisteria schaffneri.

Hofmeisteria schaffneri is used in Mexican folk medicine for treating painful gastric complaints. Therefore, in this paper the smooth muscle relaxant effect of the essential oil, and an infusion of the whole plant were evaluated using the gastrointestinal transit test in mice. The results revealed that both preparations at 316 mg/kg inhibited gastrointestinal transit by 47.5 and 52.1%, respectively. The common component of the infusion and essential oil was 8.9 -epoxy-10-acetoxythymol angelate (2), which inhibited the gastrointestinal transit by 53.4% at a dose of 31.6 mg/kg. An HPLC-UV method was developed and validated to quantify 2. The chromatographic conditions were: A LiChrospher® 100 RP-18 column (250 x 4 mm i.d., 5µm) with a mobile phase composed of CH3CN-H2O, in a gradient run at a flow rate of 0.6 mL/min, using a wavelength of 215 nm. The method was linear, precise, accurate, and showed excellent recovery. According to the results, compound 2 can be used as a marker for the quality control procedures of the crude drug of H. schaffneri.

Spasmogenic and spasmolytic activities of Agastache mexicana ssp. mexicana and A. mexicana ssp. xolocotziana methanolic extracts on the guinea pig ileum.

ETHNOPHARMACOLOGICAL RELEVANCE: Agastache mexicana has been used in traditional medicine for relief of abdominal pain and treatment of other diseases. Two subspecies have been identified: A. mexicana ssp. mexicana (AMM) and A. mexicana ssp. xolocotziana (AMX) and both are used traditionally without distinction or in combination. AIM OF THE STUDY: To determine the effect of methanol extracts of A. mexicana ssp. mexicana and A. mexicana ssp. xolocotziana on gut motility and their possible mechanism of action. MATERIALS AND METHODS: The effect of AMM and AMX methanol extracts were tested on the spontaneous activity in the isolated guinea pig ileum and on tissues pre-contracted with KCl, electrical field stimulation (EFS) or ACh. In addition, the possible mechanism of action of each subspecies on gut motility was analyzed in the presence of hexametonium, indomethacin, L-NAME, verapamil, atropine or pyrylamine. A comparative chromatographic profile of these extracts was also done to indicate the most abundant flavonoids presents in methanol extracts of both subspecies. RESULTS: AMM, but not AMX, induced a contractile effect in the guinea pig ileum. This spasmogenic effect was partially inhibited by atropine, antagonist of muscarinic receptors; and pyrilamine, antagonist of H1 receptors. In contrast, AMX, but not AMM, diminished the contractions induced by KCl, EFS or ACh. The spasmolytic activity of AMX was partially inhibited by hexamethonium, ganglionic blocker; and indomethacin, inhibitor of the synthesis of prostaglandins; but not by L-NAME, inhibitor of nitric oxide synthase. In addition, AMX diminished the maximal contraction induced by CaCl2 in a calcium-free medium. Chromatographic analyses of these methanol extracts showed the presence of acacetin and tilanin in both. CONCLUSIONS: These results suggest that in folk medicine only AMX should be used as spasmolytic, and not in combination with AMM as traditionally occurs, due to the spasmogenic effects of the latter. In addition, activation of nicotinic receptors, prostaglandins and calcium channels, but not nitric oxide mechanisms, could be responsible for the spasmolytic activity of AMX. On the other hand, release of ACh and histamine could be involved in the spasmogenic effect induced by AMM. Acacetin and tilanin are present in methanol extracts of both subspecies and both flavonoids were more abundant in AMX than AMM. Our findings contribute to the validation of the traditional use of Agastache mexicana in relieving gastrointestinal disorders, but indicate that the subspecie that should be used for this effect is A. mexicana ssp. xolocotziana.

Antihyperalgesic Activity of Rhodiola rosea in a Diabetic Rat Model.

Preclinical Research Rhodiola rosea L. (Crassulaceae) is used for enhancing physical and mental performance. Recent studies demonstrated that R. rosea had anti-inflammatory activity in animal models, for example, carrageenan- and nystatin-induced edema in rats, possibly by inhibiting phospholipase A2 and cyclooxygenases-1 and -2. In addition, R. rosea had antinociceptive activity in thermal and chemical pain tests as well as mechanical hyperalgesia. The purpose of the present study was to assess the antihyperalgesic effect of an ethanol extract of Rhodiola rosea (R. rosea) in a diabetic rat model. Rats were administered a single dose of streptozotocin (STZ; 50 mg/kg, i.p.) and hyperalgesia was evaluated four weeks later. Formalin-evoked (0.5%) flinching was increased in diabetic rats compared with nondiabetic controls Systemic (1-100 mg/kg, i.p.) and local (0.1-10 mg/paw into the dorsal surface of the right hind paw) administration of R. rosea ethanol extract dose-dependently reduced formalin-induced hyperalgesia in diabetic rats. The antihyperalgesic effect of R. rosea was compared with gabapentin. These results suggest that R. rosea ethanol extract may have potential as a treatment for diabetic hyperalgesia.

Neuroprotective effects of Tilia americana var. mexicana on damage induced by cerebral ischaemia in mice.

Tilia americana var. mexicana (T. americana) is a plant widely used in Mexico for its medicinal properties on the central nervous system. In the present study, we designed a protocol to investigate the neuroprotective effects of non-polar and polar extracts of T. americana on damage induced by cerebral ischaemia in mice. Vehicle or extracts were administered immediately after ischaemia. Functional neurological deficit, survival percentage and infarct area were determined in each experimental group. Results showed that groups treated with non-polar or polar extracts of T. americana had increased survival rate, improved neurological deficits and diminished the infarct area in relation to the ischaemic group. In conclusion, this study confirms the neuroprotective activity of T. americana, suggests a possible synergism between non-polar and polar constituents and supports its potential as a useful aid in the clinical management of stroke.

Antinociceptive activity of Ligusticum porteri preparations and compounds.

CONTEXT: The roots and rhizomes of Ligusticum porteri Coulter & Rose (Apiaceae) are widely used in Mexican folk medicine for several purposes, including painful complaints. OBJECTIVE: The main goal of this work was to demonstrate the analgesic action in mice of some preparations and major compounds from L. porteri. MATERIALS AND METHODS: The extracts, aqueous (AE) and organic (OE), the essential oil (EO) and major compounds (10-316 mg/kg) from L. porteri were evaluated as potential antinociceptive agents using the acetic acid-induced writhing and hot plate tests in ICR mice. RESULTS: All preparations tested exhibited significant antinociceptive effect in the two animal pain models selected. AE and EO were more effective in the writhing test while OE had a better effect in the hot-plate model. On the other hand, Z-ligustilide (1) provoked an increment in the latency period to the thermal stimuli in the hot-plate test at a dose of 31.6 mg/kg, and a decrease in the number of abdominal writhes at 10 mg/kg. Z-3-butylidenephthalide (2) induced a dose-dependent antinociceptive action in the hot-plate assay; this compound was also effective for controlling the pain provoked by chemical irritation at the doses of 10 and 31.6 mg/kg. Finally, diligustilide (3) inhibited the number of writhing responses at all doses tested but was inactive in the hot-plate model. CONCLUSION: The present investigation provides in vivo evidence supporting the use of L. porteri to treat painful conditions in folk medicine.

Neuroprotective evaluation of Tilia americana and Annona diversifolia in the neuronal damage induced by intestinal ischemia.

Tilia americana and Annona diversifolia are plants widely distributed in Mexico and sold in markets for their medicinal properties on the central nervous system (CNS) including possible neuroprotection. Pharmacological studies have corroborated CNS activities due to flavonoid constituents, but evidence of their neuroprotector effects are lacking. This study was conducted to test aqueous and organic extracts of these two plants for neuroprotective effects in a novel experimental model of intestinal ischemia in situ. T. americana and A. diversifolia aqueous and organic extracts were administrated to guinea pigs at an oral dose of 100 and 300 mg/kg for 15 days. Twenty four hours after the last administration, the animals were anesthetized and intestinal ischemia in situ was induced by clamping for 80 min selected branches of the superior mesenteric artery. Ischemic segments placed in an in vitro organ bath were stimulated electrically (0.3 Hz frequency, 3.0 ms duration, 14 V intensity) and chemically (ACh; 1 × 10(-9) to 1×10(-5) M). Neuroprotection was considered present when the depressed contractile response of the ischemic tissue to electrical stimulation was normalized in the treated animals. Results showed that pretreatment with the T. americana hexane and aqueous extracts, but not with those from A. diversifolia, significantly improved responses of the ischemic tissue. These results suggest that T. americana possesses neuroprotective effects against neuronal damage induced by ischemia, and that flavonoids as well as non-polar constituents are involved. Our study supports the use of this plant in folk medicine and suggests its possible effectiveness for stroke prevention.

Antimicrobial activity and chemical composition of the essential oil of Hofmeisteria schaffneri.

OBJECTIVES: The aims of this study were to establish the antimicrobial potential of Hofmeisteria schaffneri essential oil and its chemical composition. METHODS: The essential oils of Hofmeisteria schaffneri harvested at flowering (batches I and IV) and non-flowering (batches II and III) seasons were prepared by hydrodistillation and analysed by GC and GC-MS. The aqueous and organic (CH(2) Cl(2) -MeOH 1 : 1) extracts were prepared by using infusion and maceration techniques, respectively. The in-vitro antimicrobial activity of the preparations and compounds against Candida albicans and some bacteria (Gram-negative and Gram-positive) was assessed using the broth dilution method in 96-microplate wells. KEY FINDINGS: Forty-four compounds, representing ∼90% of the total constituents, were identified in the essential oil of Hofmeisteria schaffneri collected in flowering (batches I and IV) and non-flowering (batches II and III) seasons. In all cases, several thymol analogues were the major components of the oils (∼65%); some small differences in the relative proportions of these constituents were observed. The infusion exhibited an antibacterial activity against Staphylococcus aureus and Bacillus subtilis, with a MIC value of 64 µg/ml in each case. The essential oil batches were active against Staphylococcus aureus, with MIC ranging from 48 to 192 µg/ml. They were, however, inactive against Gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi (MIC > 1024 µg/ml). On the other hand, the infusion of the plant as well as the oil from batch I displayed anti-Candida albicans activity, with MIC of 128 and 192 µg/ml, respectively. Finally, the organic extract did not displayed significant activity against the tested microorganisms (MIC ≥ 1024 µg/ml). Some of the compounds isolated from the plant were also tested. Compounds 8 and 38, which were present in the essential oils, displayed the best antibacterial effect against Gram-positive bacteria (MIC ranging between 32 and 64 µg/ml). Compounds 6 (present in the infusion) and 10 (present in all preparations) showed higher activity against the yeast (MIC = 128 µg/ml) than the remaining compounds, with MIC values ranging from 256 to 512 µg/ml. CONCLUSIONS: The composition and antimicrobial activity of the oils changed slightly from flowering to non-flowering seasons. The results of the present investigation provide in-vitro scientific support for the use of the plant against skin infections in Mexican folk medicine.

Antinociceptive effect of extracts and compounds from Hofmeisteria schaffneri.

ETHNOPHARMACOLOGICAL RELEVANCE: Hofmeisteria schaffneri (Asteraceae) is a medicinal plant widely commercialized in the most important Markets of Mexico City for the treatment of gastro-intestinal complaints and skin afflictions. AIM OF THE STUDY: The main goals of this study were to establish the potential acute toxicity and the antinociceptive activity in animal models of several preparations and compounds from Hofmeisteria schaffneri. MATERIALS AND METHODS: The aqueous and organic extracts as well as the essential oil of Hofmeisteria schaffneri were prepared by infusion, maceration and hydrodistillation, respectively. Investigation of the acute toxicity was accomplished by the Lorke method. The antinociceptive effect was assessed using the writhing and the hot plate tests. Natural compounds were isolated by standard phytochemical procedures. In addition, a few thymol esters were prepared by chemical synthesis. The stability of natural and synthetic esters was qualitatively analyzed by measuring their susceptibility to hydrolysis by pig liver estearase and mouse plasma at 37 degrees C. RESULTS: The LD(50) for each preparation tested was higher than 5000 mg/kg revealing that they were not toxic to mice after exposure for short space of time. On the other hand, the extracts showed significant antinociceptive effect when tested in the hot plate model. The most active natural product as antinociceptive agent was hofmeisterin III (1) which also was the most stable in the stability study. Its pharmacological effect seems to be partially mediated by an opioid mechanism since naloxone inhibits its action. Using compound 1 as a lead molecule, several synthetic thymol esters were prepared and only compounds 13, 15 and 17 were antinoceptive at the dose of 1 mg/kg. CONCLUSIONS: The present investigation provided evidence of the efficacy of several preparations of Hofmeisteria schaffneri as antinociceptive agents. The most active preparation was the essential oil which contained large amount of hofmeisterin III (1) and other thymol derivatives. Some novel synthetic analogs of hofmeisterin III with antinociceptive properties were discovered. The nature of the ester chain of these analogs did not have a clear impact on the antinociceptive activity. The phyto-preparations analyzed in this study were not toxic to mice according to the Lorke's test; therefore considering their long term use of the plant they might be secure for human consumption.

Acute toxicity and mutagenic activity of Mexican plants used in traditional medicine.

The present work was undertaken to determine safety parameters of selected Mexican medicinal plants chosen on the basis of their frequency of medicinal use and commercial importance. The medicinal herbs included Amphipteryngium adstringens, Hintonia standleyana, Hintonia latiflora, Piper sanctum, Haemathoxylon brasiletto, Iostephane heterophylla, Valeriana procera, Arracacia tolucensis, Brickellia veronicaefolia, Scaphyglottis livida, Exostema caribaeum, Hippocratea excelsa, Ligusticum porteri, Poliomintha longiflora and Gnaphalium sp. In the acute toxicity studies in mice performed according to the Lorke procedure, Exostema caribaeum, Hippocratea excelsa, Ligusticum porteri and Poliomintha longiflora were the most toxic with LD(50) values between 1085 and 2mg/kg. The Ames test revealed that Gnaphalium sp. and Valeriana procera extracts induced mutations of S. typhimurium TA98 with or without the S9 microsomal fraction, and TA100 in the presence of the enzymatic fraction, respectively. The tincture of Valeriana procera, however, was non-mutagenic. Finally, in the Artemia salina lethality test Brickellia veronicaefolia, Arracacia tolucensis, Poliomintha longiflora and Piper sanctum caused significant mortality of the crustacean larvae with LC(50) in the range of 37-227 microg/mL.