Research Paper
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Research Paper
INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 Research Paper SYNERGISTIC HEPATOTOXIC POTENTIAL OF MANIHOT ESCULENTA CRANTZ LEAF EXTRACT ON PARACETAMOL-INDUCED LIVER DAMAGE IN RATS Awe Emmanuel O*1 , Kolawole Timothy O1, Olaniran Olutayo. B2. 1 Department of Pharmacology & Therapeutics, College of Health Sciences, Ladoke Akintola University of Technology, Osogbo Campus. 2 Department of Biomedical Sciences, College of Health Sciences, Ladoke Akintola University of Technology, Osogbo Campus. Abstract Paracetamol is an analgesic, antipyretic drug available as an over the counter (OTC) medication which causes hepatotoxicity at high doses. The effect of Manihot esculenta (100, 200 and 400mg/kg body weight, administered for 7days) on paracetamol-induced acute hepatic damage was studied by investigating the effects on liver enzymes, bilirubin, albumin, total protein and urea. Acute hepatotoxicity was induced by administering 2g/kg body weight of PCM orally on the eighth day. All the rats were sacrificed 24hours after the administration of PCM. The results shows that PCM at a dose of 2g/kg body weight induced acute hepatotoxicity 24 hours after oral administration as evident by the increase plasma alanine aminotransferase (ALT), aspertate aminotransferase (AST) and alkaline phoshatase(ALP) activities. The aqueous leaf extract of Manihot esculenta dose dependently potentiate acute hepatotoxicity induced by PCM by increasing the activities of liver enzymes but not statistically significant. In conclusion, Manihot esculenta leaf extract did not show significant hepatotoxic activities on paracetamol liver damage in rats but tends to potentiate the effect of paracetamol-induced hepatotoxicity. It was suggested that the potentiation may be due to the presence of cyanogenic glycosides. Keywords: Synergy, Manihot esculenta, paracitamol, hepatotoxicity, cyanogenic glycosides. INTRODUCTION Manihot esculenta is a woody shrub of Euphorbiaceae (spurge family) native to South America, is extensively cultivated as an annual crop in tropical and Volume 2 Issue 4 2012 subtropical regions for its edible starchy tuberous root. It’s a major source of carbohydrates [1]. Cassava is one of the most forgiving and adaptable plants. It grows well in tropical humid conditions but can also withstand www.earthjournals.org 38 INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 draught. It does well in poor soil where little else will grow and require little care. Tubers of cassava or ‘Yuka’ as the plant is commonly called in South America, are extremely rich in starch. It is the richest source of starch of any food plant (it contains up to 10 times as much as starch as corn and twice as much as potatoes). However the entire plant is poisonous if consumed raw due to its linamarin content, a precursor of cyanide glycosides. Even a relatively small content can be fatal [2]. Thus, the roots have to be rendered edible by a ritualized process of grating, washing, pulp and squeezing out of the harmful juices. Heating also renders the substances harmless [3]. There are several different species of cassava, differentiated as sweet and bitter varieties. The sweet varieties contain considerably less linamarin than the bitter types [4]. Phytochemically, the plant contains a number of oxidant compounds namely anthocyanins (flavonoids), saponions, steroids, tannins, alkaloids, anthraquinone, 3-rutinoside of kaempferol and quercetin; the cyanogenic glycosides, lotaustralin and linamarin [5-7]. The leaves can be used as a stypic, while starch mixed with rum has been used for skin problems, especially for children [8]. Cassava is used in folk remedies for various ailments such as cancer, abscesses, boils, conjuctivitis, diarrhea, dysentery, flu, hernia, inflammation, marasmus, prostatitis, sore, snake bite, fever, headache, rheumatism and hemorrhoids [9-11].In Nigeria, cassava leaves are also used in the treatment of ringworms, conjuctivitis, sores and abscesses [8]. Some ethno medicinal uses of Manihot esculenta plant have been validated Volume 2 Issue 4 2012 scientifically, and the plant´s leaf extract was reported to produce dose-related, sustained and significant reduction in fresh egg albumin-induced acute inflammation in rat paw oedema [12]. Chloroform extract of leaf of Manihot esculenta has been reported to have activity against bacteria such as V. cholera, Shigella flexneri, S. thyphi, P. auruginosa [13]. In addition, the crude extract of Manihot esculenta showed dose-dependent inhibitory effect on the production of lipid peroxides in rats [14]. Anti helmintic and antipyretic activities of the leaf extract have also been reported [15-16]. It has been shown that liver damage is caused by chemicals such as paracitamol and carbon tetrachloride in large doses [17-18], therefore, this study was designed to evaluate possible synergistic hepatotoxic potential of aqueous Manihot esculenta leaf extract on paracitamolinduced liver damage in rat. MATERIALS AND METHODS Ethical consideration Experimental procedures and protocols used in this study were approved by the Ethics committee of the Ladoke Akintola University of Technology, Nigeria and conform to the “Guide to the care and use of animals in research and teaching” (NIH publications number 85-93 revised in 1985) Plant collection Cassava leaves were collected at a farm in Dada Estate, Egbedore Local Government, Osogbo, Osun State. The leaves were identified by a taxonomist, Mr. Odewo, at the herbarium of the Federal Institute of Forest Research Ibadan where voucher specimen was deposited. www.earthjournals.org 39 INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 Extraction Mannihot esculenta fresh leaves (1kg) were air-dried at room temperature. The air-dried leaves of the plant were milled into fine powder in a Waring commercial blender. The powdered leaves were macerated in 3 liters of water at room temperature (27± 1 C) and extracted for 48 hours with occasional shaking. The combined water extract was filtered and concentrated to dryness under reduced pressure at 60 ± 1o C in rotary evaporator. Freeze-drying and solvent elimination of the resulting aqueous extract was weighed and finally gave 40.78 g. The percentage yield was calculated using this formula: weight of extract/original weight x 100 giving 4.0.35% yields) of brown powdery crude Manihot esculenta leaf extract (MEE). A stock solution of 10mg/ml was prepared by dissolving 100mg of leaf extract in 10ml of water. Different doses were calculated from the stock solution. Animals Healthy, male and female healthy young adult, Wistar rats (Rattus norvegicus) weighing 220–250 g, were used. The animals were kept and maintained under laboratory conditions of temperature and humidity with a 12 h light/dark cycles. They were allowed free access to food (standard pellet diet) and drinking tap water ad libitum. Determinations of Acute Oral Toxicity (LD50) Acute oral toxicity (AOT) of methanol extract was determined as per OECD guidelines. The animals were fasted 3 h prior to the experiment and as per up and down procedure (OECD 2001). Animals were administered with single dose of aqueous extract and observed for its mortality for 48 h study period (short Volume 2 Issue 4 2012 term) toxicity. Based on short-term profile of drug, the dose of next animals was determined as per as OECD guideline 425. All the animals were also observed for long term toxicity (14 Days). HEPATOTOXIC ACTIVITIES The animals were divided into five groups of six animals in each group. The extract was given to the animals for seven days. On the eighth day, paracetamol was given to cause liver damage. Group I: Negative control i.e. untreated Group II: Positive control. Received 2000mg/kg of paracetamol on the 8th day Group III: Received 100mg/kg of plant extract for 7 days and 2000mg/kg of paracetamol on the 8th day Group IV: Received 200mg/kg of plant extract for 7 days and 2000mg/kg of paracetamol on the 8th day Group V: Received 400mg/kg of plant extract for 7 days and 2000mg/kg of paracetamol on the 8th day Collection of blood sample Heparinized and EDTA blood samples were obtained under light anesthesia from the orbital sinus using microhaematocrit tubes [19-20] for analysis of biochemical and hematological parameters respectively. All animals were sacrificed by exsanguinations after light ether inhalation anesthesia at the end of the experiment. The animals were subjected to post-mortem examination with collection of sample from the liver. Histopathological examination The liver tissues obtained from sacrificed animals were fixed in 10% neutral buffered formalin for at least 48 h. Liver sections (4-5 µm) paraffin wax were processed and stained with haematoxylin www.earthjournals.org 40 INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 and eosin for microscopic examination using standard protocol of Carleton, (1980) [21]. Statistical analysis The data are presented as mean± SEM and analyzed by one-way ANOVA, followed by independent’s test. P values < 0.05 were considered significant RESULTS PCM at a dose of 2g/kg body weight induced acute hepatotoxicity 24hours after oral administration as evident by significant increase (P<0.05) in plasma ALT, AST and ALP (37.20±3.42, Table 1: Effects of hepatoxicity in rats 80.20±6.22 and 18.50±2.51) values compared to normal control (23.40±3.44, 53.00±4.64 and 10.28±1.47). The aqueous leaf extract of Manihot esculenta dose dependently and significantly increase (P<0.05) the values of ALT, AST and ALP (36.60±2.70, 36.60±2.70 and 38.20±5.59), but not statistically significant (P>0.05) when compared to PCM-induced group. Table 1. There were dose-dependent increase in liver tissue degenerations compared to the normal control and PCM-induced liver damaged (untreated) control (Fig 1A, B, D and E). on biochemical parameters in paracitamol-induced M. esculenta GROUP ALT(IU/L) AST (IU/L) ALP (IU/L) BILIRUBIN (mg/dl) ALB (g/l) TP (g/l) BUN(mmo l/l) NEGATIVE CONTROL 23.40±3.44 53.00±4.64 10.28±1.47 10.10±1.26 34.80±2.86 72.40±3.97 11.18±2.20 POSITIVE CONTROL 37.20±3.42* 80.20±6.22 * 18.50±2.51* 11.44±2.21 32.06±2.00 72.20±2.59 12.06±0.81 36.60±2.70* 81.60±7.83 * 19.78±3.39* 11.08±1.99 29.40±1.14 70.80±2.49 12.46±0.61 38.20±5.59* 83.00±7.52 * 19.38±3.67* 12.04±1.82 26.80±2.39 68.20±4.27 10.84±0.88 40.40±3.36* 84.80±5.89 * 22.38±2.47* 12.94±2.06 27.40±3.13 69.60±6.11 11.10±3.53 100mg/kg EXTRACT +2000mg/kg PARACETA MOL 200mg/kg EXTRACT + 2000mg/kg PARACETA MOL 400mg/kg EXTRACT +2000mg/kg PARACETA MOL Volume 2 Issue 4 2012 www.earthjournals.org 41 INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 D A B E C Fig 1: Histopathological changes in the liver A: control showing normal hepatocytes, central veins and biliary tracts B: Liver showing fewer vessels with inflammatory lesions ((PCM alone) C: Liver section showing bloated hepatocytes with many inflammatory cells D: Liver section showing loss of tissue architecture and inflammatory lesions ((200mg/kg of extract + 2g/kg of PCM) E showing loss of tissue architecture with mass degeneration of hepatocytes suggestive of hepatic failure (400mg/kg of extract + 2g/kg of PC Volume 2 Issue 4 2012 www.earthjournals.org 42 INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 DISCUSSION Paracetamol toxicity is due to the formation of toxic metabolites when a part of it is metabolized by cytochrome P450. Introduction of cytochrome or depletion of hepatic glutathione is a prerequisite for paracitamol-induced hepatotoxicity [22]. So in the present study, paracitamol was employed as toxic agent and the hepatotoxic effect of aqueous Manhot esculenta leaf extract against the paracetamol induced hepatotoxicity was studied. The extent of toxicity was estimated by histopathological studies and biochemical markers like, ALT, AST, ALP, bilirubin, total protein, albumin and BUN levels. The present study reports the potential hepatotoxic activity of Manihot esculenta leaf extract against hepatic injury produced by paracetamol in rats. Paracitamol is known as antipyretic and analgesic agent, which is safe in therapeutic doses, but can produce fatal hepatic necrosis with high dose. It is employed as an experimental hepatotoxic agent [23]. The hepatic cytochrome P450 enzyme system metabolizes paracitamol, forming a minor yet significant alkylating metabolite known as NAPQI. NAPQI is then irreversibly conjugated with the sulfhydryl groups of glutathione [24]. NAPQI depletes glutathione and initiates covalent binding to cellular proteins. These events lead to the disruption of calcium homeostasis, mitochondrial dysfunction, and oxidative stress and may eventually culminate in cellular damage and death [24]. Volume 2 Issue 4 2012 Reinforcing the above stated mechanisms, biochemical parameters (liver enzymes) demonstrate significant increase in groups that received toxic dose of paracitamol in the present study. Histopathological profile also reveals a major damage in the same groups. Thus, it clearly shows that, toxicity is due to either of the above mechanisms such as depletion of glutathione store or free radical generation or lipid peroxidation. Normally, AST and ALT are present in high concentration in the liver cells and are released from the cells due to hepatocyte necrosis, resulting to their increase in the blood. ALT is a sensitive indicator of acute liver damage and elevation of this enzyme is a common feature in hepatic damage. ALT is more selectively a liver parenchymal enzyme than AST [25]. Liver function is assessed by estimating the activities of plasma ALT, AST, ALP, bilirubin, albumin and total protein. In liver damage, these enzymes leak into the blood stream in conformity with the extent of damage [26]. The elevated levels of these enzymes (ALT, AST and ALP) observed in group 2 (paracitamol treated rats) in this present study corresponds to the extensive liver damage induced by paracetamol. The increase in the concentrations of the liver enzymes observed in groups III–V, although not significant, might probably be due to M .esculenta leaf extract toxicity. Plasma ALP and total bilirubin levels are also related to the status and function of hepatic cells. High serum level of ALP is due to its increase synthesis and biliary pressure [27]. In this present study, it was www.earthjournals.org 43 INTERNATIONAL JOURNAL OF PHARMACOLOGY AND THERAPEUTICS ISSN 2249 – 6467 observed that M. esculenta leaf extract (100, 200, 400 mg/kg), slightly increase plasma ALP and bilirubin levels though not statistically significant (p>0.05) when compared to paracetamol control group. This clearly shows that the plant extract shows no hepatoprotective activity, but tends to potentiate the damage caused by paracitamol toxicity. Hypoalbuminaemia is most frequent in chronic liver disease hence decrease in total protein content is an indicator and useful index of the severity of cellular dysfunction in chronic liver damage[27]. The lowered level of albumin recorded in plasma of rats that received 2000 mg/kg of paracitamol reveals the severity of hepatic damage. There was significant decrease (p>0.05) in albumin level of rats that received M. esculenta leaf extract at doses of 100, 200, 400 mg/kg compared to paracitamol control group. This shows that M. esculenta leaf extract possess no hepatoprotective activity, but potentiates liver damage as a result of paracitamolinduced liver toxicity. Blood urea nitrogen of the hepatotoxic groups is normal when compared to the normal control group (p>0.05). This indicates that no injury was caused to the kidney as a result of M. esculenta leaf extract and paracitamol-induced toxicity. M. esculenta leaf extract toxicity may be as a result of the presence of cyanogenic glucosides. The presence of cyanoglycosides, linamarin and lotaustralin pose potential toxic effect. Linamarin is hydrolysed by intestinal luminal bacterial beta glucosidase to release hydrogen cyanide which can cause acute poisoning [28-30]. It has been Volume 2 Issue 4 2012 reported that cassava leaf contains a number of antioxidant compounds namely α-carotene, vitamin C, vitamin A, anthocyanin (flavonoid), saponins and steroids [31] but they do not offer any protective activity to the liver cells. CONCLUSION The results obtained from the present study suggest that M. esculenta leaf extract did not show hepatoprotective activity, but potentiates liver damage induced by paracitamol. REFERENCES [1]. Phillips, T.P. (1984): An overview of cassava production and consumption. Development Research Centre Monograph. Pp 82-88. [2]. Jesus, V.S., Moraes, C.F. Telles, F.F.F. (1986): Estimation of hydrogen cyanide in cassava plant. Rev. Bras. Mand. Cruz das almas. 5, 83-90. [3]. Cooke, R.D. (1983): Effect of cassava processing on residual cyanide. F. Dalange and R. Ahluwalia, eds. Pp. 138-142 [4]. Dafour, D.L. (1989): Effectiveness of cassava detoxication techniques used by indigenous people in North-West Amazonia. Interciencia. 14:86-91 [5].Okeke E.C, H.N Eneobong, A.O Uzuegbunam, A.O Ozioko, S. Umeh and H. Kuhnlein 2009. Nutrients composition of Traditional Foods and Their contributions to Energy and Nutrient Intakes of Children and Women in Rural Household in Igbo Culture Area. 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