Cerebroprotective activity of Wedelia calendulacea on global cerebral ischemia in rats

The present study was to investigate the effect of W. calendulacea on ischemia and reperfusion-induced cerebral injury. Cerebral ischemia was induced by occluding right and left common carotid arteries (global cerebral ischemia) for 30 min followed by reperfusion for 1 h and 4 h individually. Various biochemical alterations, produced subsequent to the application of bilateral carotid artery occlusion (BCAO) followed by reperfusion viz. increase in lipid peroxidation (LPO), hydrogen peroxide (H2O2), and decrease in reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD), level in the brain tissue, Western blot analysis (Cu-Zn-SOD and CAT) and assessment of cerebral infarct size were measured. All those enzymes are markedly reversed and restored to near normal level in the groups pretreated with W. calendulacea (250 and 500 mg/kg given orally in single and double dose/day for 10 days) in dose-dependent way. The effect of W. calendulacea had increased significantly the protein expression of copper/zinc superoxide dismutase (Cu-Zn-SOD) and CAT in cerebral ischemia. W. claendulacea was markedly decrease cerebral infarct damages but results are not statistically significant. It can be concluded that W. calendulacea possesses a neuroprotective activity against cerebral ischemia in rat.     

Activity of Wedelia calendulacea Less. in post-menopausal osteoporosis

Wedelia calendulacea Less., a perennial herb containing isoflavanoids, is used in liver disorders, uterine hemorrhage and menorrhagia. Osteoporosis in women occurs mainly due to estrogen deficiency following menopause. Studies indicate that isoflavones are estrogenic enough to promote bone formation. Our study was aimed to investigate the antiosteoporotic effect of the ethanol extract of W. calendulacea in the ovariectomized rat model of osteoporosis, at two different dose levels of 500 and 750 mg/kg/body wt. day. The findings, assessed on the basis of biomechanical and biochemical parameters, showed that the ethanol extract of the plant had a definite protective effect. This was further supported by the histopathological studies. Phytochemical investigation revealed the presence of isoflavones and wedelolactone, which are known to act as phytoestrogens and may be responsible for the antiosteoporotic activity.     

Plant–soil feedback during biological invasions: effect of litter decomposition from an invasive plant (Sphagneticola trilobata) on its native congener (S. calendulacea)

生物入侵过程中的植物-土壤反馈：一种入侵植物的凋落物分解对其本地近缘植物的影响 植物入侵可通过正或负的植物-土壤反馈效应改变土壤的生物和非生物性质,从而影响入侵栖息地的土壤理化性质。许多入侵物种的凋落物分解可增加土壤养分,降低本地植物多样性,并导致进一步的植物入侵。关于入侵植物凋落物在不同土壤类型及深度分解及反馈效应的研究依然很少。本研究旨在明确入侵植物南美蟛蜞菊(Sphagneticola trilobata)凋落物在不同土壤类型和不同土壤深度条件下的分解情 况及其对本地近缘植物蟛蜞菊(S. calendulacea)生理生长的影响。将装有南美蟛蜞菊凋落物的尼龙袋加入到不同深度(即0、2、4 和6 cm)的砂土、营养土和粘土中,经6个月的分解后,回收凋落物袋并计算分解速率,随后在凋落物分解处理后的土壤中种植本地蟛蜞菊,并在生长期结束时测量其生理生态指标。研究结果表明,所有处理土壤类型中,凋落物在土壤深度为2和4 cm处分解后显著增加了土壤养分,而对本 地蟛蜞菊的叶片叶绿素、叶氮含量等生长指标表现为负效应。因此,入侵植物南美蟛蜞菊凋落物分解对土壤养分表现为正的反馈效应,而对本地植物蟛蜞菊的生长表现为负效应。我们的研究结果还表明,入侵植物的凋落物分解对土壤和本地物种的影响还因凋落物分解所在的土壤深度而显著不同。未来的研究应侧重于入侵栖息地中更多本地和入侵物种的植物-土壤反馈效应,以及更多土壤类型和土壤深度的入侵植物凋落物效应。     

Paracetamol and conventional antimalarial drugs induced hepatotoxicity and its protection by methionine in rats

Hepatotoxicity, induced in rats, by treatment with high doses of paracetamol and chloroquine was confirmed by estimating blood transaminase levels. Hepatoprotective effect was determined by administering combination of methionine (10% of paracetamol/chloroquine, p.o.) and hepatotoxic drugs quinine. The results were confirmed by histopathological examination of liver. Paracetamol (7 g/kg) and chloroquine (970 mg/kg) administration increased significantly the transaminase levels. Methionine alone did not produced any change. Hepatonecrosis induced by paracetamol, chloroquine alone and their combinations and its protection with methionine was revealed by histopathological study whereas the combination of paracetamol and methionine showed no significant histopathological difference when compared to the normal liver section. The results reveal that, methionine significantly prevented the rise in transaminases levels produced by hepatotoxic doses of paracetamol and chloroquine. But, to prevent occasional cases of paracetamol overdosage, it is not advisable to give methionine concurrently with paracetamol to patients who are taking paracetamol therapeutically.     

Hepatoprotective activity of Azadirachta indica leaves on paracetamol induced hepatic damage in rats.

Effect of A. indica leaf extract on serum enzyme levels (glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, acid phosphatase and alkaline phosphatase) elevated by paracetamol in rats was studied with a view to observe any possible hepatoprotective effect of this plant. It was interesting to observe that serum enzyme levels were much elevated in paracetamol induced animals than in those receiving a combination of paracetamol and lead extract. It is stipulated that the extract treated group was protected from hepatic cell damage caused by paracetamol induction. The findings were further confirmed by histopathological study of liver.     

Increased frequency of sister-chromatid exchange and chromatid breaks in lymphocytes after treatment of human volunteers with therapeutic doses of paracetamol

Paracetamol was given to 10 healthy human volunteers in 3 doses of 1 g each during a period of 8 h. Blood samples for lymphocyte cultures were taken before and 24 h after paracetamol administration. A small but significant increase was found in the frequency of sister-chromatid exchanges (SCE) after intake of paracetamol (0.187 +/- 0.030 per chromosome before and 0.208 +/- 0.024 per chromosome after). After exposure the mean frequency of chromatid breaks per 100 cells was significantly increased (2.16 +/- 1.33 versus 0.33 +/- 0.50 before exposure). Exposure of human lymphocytes in vitro showed that concentrations of paracetamol above 0.1 mM induced inhibition of replicative DNA synthesis. Increased SCE was found in lymphocytes exposed to 1-10 mM paracetamol for 2 h. Furthermore, 0.75-1.5 mM paracetamol exposure for 24 h increased the frequency of chromatid and chromosome breaks in the lymphocytes. The paracetamol-induced SCE and chromosome aberrations may be secondary effects of paracetamol-induced inhibition of DNA synthesis or due to covalent binding of paracetamol metabolite(s) to DNA.     

Identification and characterization of coumestans as novel HCV NS5B polymerase inhibitors

The hepatitis C virus (HCV) NS5B is essential for viral RNA replication and is therefore a prime target for development of HCV replication inhibitors. Here, we report the identification of a new class of HCV NS5B inhibitors belonging to the coumestan family of phytoestrogens. Based on the in vitro NS5B RNA-dependent RNA polymerase (RdRp) inhibition in the low micromolar range by wedelolactone, a naturally occurring coumestan, we evaluated the anti-NS5B activity of four synthetic coumestan analogues bearing different patterns of substitutions in their A and D rings, and observed a good structure-activity correlation. Kinetic characterization of coumestans revealed a noncompetitive mode of inhibition with respect to nucleoside triphosphate (rNTP) substrate and a mixed mode of inhibition towards the nucleic acid template, with a major competitive component. The modified order of addition experiments with coumestans and nucleic acid substrates affected the potencies of the coumestan inhibitors. Coumestan interference at the step of NS5B-RNA binary complex formation was confirmed by cross-linking experiments. Molecular docking of coumestans within the allosteric site of NS5B yielded significant correlation between their calculated binding energies and IC(50) values. Coumestans thus add to the diversifying pool of anti-NS5B agents and provide a novel scaffold for structural refinement and development of potent NS5B inhibitors.     

Synthesis and preliminary pharmacological evaluation of coumestans with different patterns of oxygenation

Five coumestans with different patterns of oxygenation in rings A and D were synthesized from resorcinol and aromatic aldehydes, and screened for their antimyotoxic activity. The most potent compound (2b, IC50 = 1 microM) was selected for study of its pharmacological profile.     

Hepatoprotective activity of Hemidesmus indicus R. br. in rats

Treatment of rats with paracetamol and CCl4 produced a significant increase in the levels of serum glutamate pyruvate transaminase (SGPT), serum glutamate oxaloacetate transaminase (SGOT), alkaline phosphatase (ALP), total and direct bilirubin. Rats pretreated with methanolic extract of roots of H. indicus (100-500 mg/kg body weight, po) exhibited rise in the levels of these enzymes but it was significantly less as compared to those treated with paracetamol or CCl4 alone. The results of methanolic extract of H. indicus were comparable with the standard hepatoprotective agent silymarin (100 mg/kg). Maximum hepatoprotective effect was found to be at the dose of 250 mg/kg body weight in case of CCl4 induced hepatic damage while 500 mg/kg body weight in case of paracetamol induced hepatic damage. The results suggest that methanolic extract of H. indicus roots possesses a potential antihepatotoxic activity.     

Genotoxic effects of paracetamol in V79 Chinese hamster cells

Paracetamol was studied for possible genotoxic effects in V79 Chinese hamster cells. Paracetamol (0.5 mM for 30 min) reduced the rate of DNA synthesis in exponentially growing V79 cells to about 50% of control. A further decrease in the DNA synthesis was seen during the first 30 min after termination of paracetamol exposure. Paracetamol (3 and 10 mM for 2 h) caused a small increase in DNA single-strand breaks, as measured by the alkaline elution technique. After 16 h elution, the amount of DNA retained on the filters was 79 and 70% of controls in cells treated with 3 and 10 mM paracetamol respectively. No indication of DNA damage was seen in measuring the effect of paracetamol (0.25-10 mM for 2 h) on unscheduled DNA synthesis in growth-arrested cultures of V79 cells. At the highest concentrations (3 and 10 mM paracetamol), decreased unscheduled DNA synthesis was observed. Also UV-induced DNA-repair synthesis was inhibited by 3 and 10 mM paracetamol. DNA-repair synthesis was, however, inhibited at a much higher concentration than that inhibiting replicative DNA synthesis. The number of sister-chromatid exchanges (SCE) increased in a dose-dependent manner on 2 h exposure to paracetamol from 1 mM to 10 mM. At the highest dose tested (10 mM), the number of SCE increased to 3 times the control value. Co-culturing the V79 cells with freshly isolated mouse hepatocytes had no further effect on the paracetamol induced sister-chromatid exchanges. The present study indicates that paracetamol may cause DNA damage in V79 cells without any external metabolic activation system added.     

UK legislation on analgesic packs: before and after study of long term effect on poisonings

Objective To evaluate the long term effect of legislation limiting the size of packs of analgesics sold over the counter.Design Before and after study.Setting Suicides in England and Wales, data from six liver units in England and Scotland and five general hospitals in England, and UK data on sales of analgesics, between September 1993 and September 2002.Data sources Office for National Statistics; six liver units in England and Scotland; monitoring systems in general hospitals in Oxford, Manchester, and Derby; and Intercontinental Medical Statistics Health UK.Main outcome measures Deaths by suicidal overdose with paracetamol, salicylates, or ibuprofen; numbers of patients admitted to liver units, listed for liver transplant, and undergoing transplantations for paracetamol induced hepatotoxicity; non-fatal self poisonings with analgesics and numbers of tablets taken; and sales figures for analgesics.Results Suicidal deaths from paracetamol and salicylates were reduced by 22% (95% confidence interval 11% to 32%) in the year after the change in legislation on 16 September 1998, and this reduction persisted in the next two years. Liver unit admissions and liver transplants for paracetamol induced hepatotoxicity were reduced by around 30% in the four years after the legislation. Numbers of paracetamol and salicylate tablets in non-fatal overdoses were reduced in the three years after the legislation. Large overdoses were reduced by 20% (9% to 29%) for paracetamol and by 39% (14% to 57%) for salicylates in the second and third years after the legislation. Ibuprofen overdoses increased after the legislation, but with little or no effect on deaths.Conclusion Legislation restricting pack sizes of analgesics in the United Kingdom has been beneficial. A further reduction in pack sizes could prevent more deaths.     

Paracetamol-stimulated lipid peroxidation in isolated rat and mouse hepatocytes

Treatment of isolated hepatocytes from 3-methylcholanthrene induced rats with 1 mM paracetamol has been found to greatly decrease cellular reduced glutathione (GSH) content and to promote lipid peroxidation, evaluated as malonaldehyde (MDA) production and conjugated diene absorbance. A similar dosing of hepatocytes from phenobarbital-induced or normal rats is ineffective in that respect. On the other hand, the aspecific stimulation of the cytochrome P-450-mediated paracetamol activation due to acetone addition further increases GSH depletion as well as MDA production.Isolated hepatocytes with basal low GSH content are also more susceptible to paracetamol-induced lipid peroxidation, indicating that the rate of the drug metabolism and the cellular GSH content are critical factors in the determination of such peroxidative attack.In isolated mouse liver cells paracetamol does not require preliminary cytochrome P-450 induction to stimulate MDA formation, even at concentrations ineffective in rat cells.However, 5 mM paracetamol, despite a great depletion of cellular GSH content, does not promote MDA formation either in the rat or in the mouse hepatocytes. This effect may be due to the ability of paracetamol to scavenge lipid peroxides under defined conditions, as tested in various lipid peroxidizing systems.Membrane leakage of lactate dehydrogenase (LDH) is evident in paracetamol treated cells undergoing lipid peroxidation, but not when MDA formation is inhibited by high doses of the drug or by addition of antioxidants such as α-tocopherol and diphenylphenylenediamine (DPPD).Nevertheless in these conditions the covalent binding of activated paracetamol metabolites is not affected, suggesting that lipid peroxidation might play a role in the pathogenesis of liver damage following paracetamol overdose.     

COX-3 and the mechanism of action of paracetamol/acetaminophen

Paracetamol produces analgesia in the mouse writhing test through a central action which is paralleled by a reduction in brain PGE(2) concentrations. In contrast, diclofenac has a peripheral analgesic action in this test. Paracetamol-induced hypothermia is also accompanied by a reduction in brain PGE(2) concentrations in C57/Bl6 mice. This hypothermic effect of paracetamol was reduced in COX-1 but not in COX-2 gene-deleted mice. These results support the view that analgesia and hypothermia due to paracetamol are mediated by inhibition of a third COX isoenzyme (designated COX-3). In cultured mouse macrophages, COX-2 is induced by treatment with LPS or with high concentrations of diclofenac. Diclofenac-induced COX-2 is inhibited with low concentrations of paracetamol, whereas LPS-induced COX-2 is insensitive to paracetamol inhibition. The mechanisms of induction and possibly the functions of these two COX-2 enzymes are also different.     

The degradation of paracetamol (4-hydroxyacetanilide) and other substituted acetanilides by aPenicillium species

A mould which was isolated from a solution of paracetamol was identified as aPenicillium species and was found to possess the ability to utilise a series of substituted acetanilides, including paracetamol (4-hydroxyacetanilide), phenacetin (4-ethoxyacetanilide) and metacetamol (3-hydroxyacetanilide) as sole carbon sources for growth. Studies with washed-cell suspensions indicated that growth of thePenicillium isolate in the presence of paracetamol induced the respective enzyme systems for the degradation of this compound. Manometric studies, measuring oxygen uptake rates, indicated that the mould was capable of degrading paracetamol to acetate and 4-aminophenol. Acetate was further metabolised whilst 4-aminophenol accumulated in the growth medium and was subsequently identified by UV spectroscopy and thin-layer chromatography. Similar experiments with phenacetin indicated metabolism by the mould to acetate and 4-ethoxyaniline which was isolated and identified by subsequent analysis of the growth medium. However, unlike 4-aminophenol and 4-ethoxyaniline, the degradation product (3-aminophenol) from metacetamol metabolism was further degraded by the mould.     

Molecular interaction of human serum albumin with paracetamol: Spectroscopic and molecular modeling studies

The interaction between paracetamol and human serum albumin (HSA) under physiological conditions has been investigated by fluorescence, circular dichroism (CD) and docking. Fluorescence data revealed that the fluorescence quenching of HSA by paracetamol was the result of the formed complex of HSA–paracetamol, and the binding constant (K_a) and binding number obtained is 1.3 × 10⁴ at 298 K and 2, respectively for the primary binding site. Circular dichorism spectra showed the induced conformational changes in HSA by the binding of paracetamol. Moreover, protein–ligand docking study indicated that paracetamols (two paracetamols bind to HSA) bind to residues located in the subdomain IIIA.     

Genotoxicity of analgesic compounds assessed by an in vitro micronucleus assay

Several analgesic compounds and mixtures of analgesics were examined for both cytotoxicity and ability to induce chromosomal damage in the normal rat-kidney cell line NRK-49F. Chromosomal damage was assessed using an in vitro micronucleus assay. Of all the compounds tested, only N-hydroxyparacetamol caused a high degree of cell death at the concentrations used. 4 analgesic compounds were found to be inducers of micronuclei in NRK cells; in order of decreasing potency these were: N-hydroxyparacetamol, N-hydroxyphenacetin, caffeine and paracetamol. An aspirin, phenacetin, caffeine mixture (APC) failed to induce micronuclei above the background level, and a paracetamol-codeine combination did not increase the level of micronuclei induction above that induced by paracetamol alone. This report suggests paracetamol and some related compounds are capable of inducing chromosomal damage in mammalian cells in vitro, which is consistent with recent reports of a possible paracetamol-DNA interaction.     

Antioxidant and hepatoprotective activity of Aphanizomenon flos-aquae Linn against paracetamol intoxication in rats

Paracetamol caused liver damage as evident by significant increase in the activities of aspartate and alanine transferases. There were general statistically significant losses in the activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione transferase and an increase in thiobarbituric acid reactive substances in the liver of paracetamol treated group compared with the control group. However, treatment with ethanol extract of A. flos-aquae (EEAFA) was able to counteract these effects. Protection offered by silymarin (standard reference drug) seemed relatively greater. The results suggest that EEAFA can act as hepatoprotective agent against paracetamol induced toxicity as an antioxidant.     

Hepatoprotective activity of Psidium guajava Linn. leaf extract

The study was designed to evaluate the hepatoprotective activity of P. guajava in acute experimental liver injury induced by carbon tetrachloride, paracetamol or thioacetamide and chronic liver damage induced by carbon tetrachloride. The effects observed were compared with a known hepatoprotective agent, silymarin. In the acute liver damage induced by different hepatotoxins, P. guajava leaf extracts (250 and 500mg/kg, po) significantly reduced the elevated serum levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and bilirubin. The higher dose of the extract (500 mg/kg, po) prevented the increase in liver weight when compared to hepatoxin treated control, while the lower dose was ineffective except in the paracetamol induced liver damage. In the chronic liver injury induced by carbon tetrachloride, the higher dose (500 mg/kg, po) of P. guajava leaf extract was found to be more effective than the lower dose (250 mg/kg, po). Histological examination of the liver tissues supported the hepatoprotection. It is concluded that the aqueous extract of leaves of guava plant possesses good hepatoprotective activity.     

Analgesic efficacy and safety of paracetamol-codeine combinations versus paracetamol alone: a systematic review.

OBJECTIVES--To assess whether adding codeine to paracetamol has an additive analgesic effect; to assess the safety of paracetamol-codeine combinations versus paracetamol alone. DESIGN--Systematic literature review with meta-analysis, methodological quality of published trials being scored by means of 13 predefined criteria. TRIALS--24 of 29 trials that met the inclusion criteria. Models studied in the trials were postsurgical pain (21), postpartum pain (one), osteoarthritic pain (one), and experimentally induced pain (one). INTERVENTIONS--Dosages ranged from 400 to 1000 mg paracetamol and 10 to 60 mg codeine. MAIN OUTCOME MEASURES--The sum pain intensity difference (efficacy analysis) and the proportion of patients reporting a side effect (safety analysis). RESULTS--Most trials were considered of good to very good quality. Only the single dose studies could be combined for analysis of analgesic efficacy. Pooled efficacy results indicated that codeine added to paracetamol provided a 5% increase in analgesia on the sum pain intensity difference. This effect was comparable to the difference in analgesic effect between codeine and placebo. The cumulative incidence of side effects with each treatment was comparable in the single dose trials. In the multidose studies a significantly higher proportion of side effects occurred with paracetamol-codeine preparations. CONCLUSION--The difference is analgesic effect between paracetamol-codeine combinations and paracetamol alone was small but statistically significant. In the multidose studies the proportion of patients reporting a side effect was significantly higher with paracetamol-codeine combinations. For occasional pain relief a paracetamol-codeine combination might be appropriate but repeated use increases the occurrence of side effects.     

Cardioprotective effects of nitroparacetamol and paracetamol in acute phase of myocardial infarction in experimental rats

We aimed to determine whether nitroparacetamol (NO-paracetamol) and paracetamol exhibit cardioprotective effects. Myocardial infarction (MI) was induced in rats, and drug treatment was started 1 wk before surgery. Mortality rate and infarct size at 2 days after MI were compared. Treatment groups included vehicle (saline), paracetamol (5 mg x kg(-1) x day(-1)) and NO-paracetamol (15 mg x kg(-1) x day(-1)). Mortality rates for vehicle (n = 80), paracetamol (n = 79), and NO-paracetamol (n = 76) groups were 37.5%, 21.5%, and 26.3%, respectively. Infarct size for the vehicle group was 44.8% (+/-6.1%) of the left ventricle (LV). For the paracetamol and NO-paracetamol groups, infarct size was 31.3% (+/-5.6%) and 30.7% (+/-8.1%) of the LV, respectively. Both paracetamol- and NO-paracetamol-treated groups showed increased activities of catalase and SOD compared with the vehicle group. They could attenuate endothelial, inducible, and neuronal nitric oxide synthase and cyclooxygenase-1 and -2 gene expression after MI. The observation indicates the potential clinical significance of the cardioprotective effects of these drugs.