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Journal of Biological Sciences

Year: 2007 | Volume: 7 | Issue: 7 | Page No.: 1293-1295
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ABSTRACT

Toxicity studies on the methanolic extract of Portulaca oleracea L. were carried out on mice intraperitoneally. The LD50 was calculated using the methods of Miller and Tainter (LD50, 1853.5 mg kg-1), Reed and Muench (LD50, 1871 mg kg-1) and Karber method (LD50, 1875 mg kg-1) these values placed the plant to be moderately toxic. Histopathological findings revealed that the extract has effect on the kidney, lung and liver in a dose dependent manner.
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INTRODUCTION

Portulaca oleracea L. (commonly called purslane) is an herbaceous weed widely distributed throughout the World. It is known by indigenous tribes of Nigeria as Fasa kasa, in Hausa, Papasan in Yoruba and Efere makara in Efik (Burkill, 1997).

The plant has been used as vegetable and for medicinal purpose for hundreds of years. The ancient Egyptians use it for heart failures and heart disease. In Africa purslane has been used as antibacterial, anti-diabetic, antihelmintic, antiscorbutic, diuretic and as pain reliever in haemorrehoid and whitlow. The seeds are demulcent, carminative, diuretic and slightly astringent (Burkill, 1997; Boulus et al., 1984; Iwu, 1993). Externally, the plant has been used to treat burns, earache, insect stings and inflammations and skin diseases (Leung and Forster, 1996).

P. oleracea has been shown to exhibit antibacterial, antifungal, anti-inflammatory, diuretic (4), anti-convulsant and analgesic activity (Chan et al., 2000). Gholamreza et al. (2004) also showed the administration of the aqueous and ethanolic extracts of purslane has some beneficial preventive effect on gastric ulcers induced by HCl or ethanol and reduce the gastric acidity in pylorus-ligated mice Chemically, P. oleracea contain many biologically active compounds, some of them being nutritive. Some of the biologically active (and in some case, potentially toxic compounds) include free oxalic acids, alkaloids, omega-3 fatty acids, coumarins, tannins, flavonoids, cardiac glycosides and anthraquinone glycosides. It has high contents of Omega-3 fatty acids and protein compared to other vegetables (Ezekwe, 1999) monoterpene- portuloside A-was also isolated from the plant- P. oleracea and is said to be rich in vitamins (Sakai, 1996) essential minerals (WHO, 1990; Keys, 1976) and fatty acids such as omega-3 acids (Bown, 1995).

Despite these numerous uses and the various chemical constituents reported in P. oleracea, no data on the toxicity of the plant could be found in the available literature, although the plant is reported to contain cardiac glycosides and oxalic acids, which can be toxic. This work is therefore aimed at establishing the safety or otherwise of P. oleracea with regard to its numerous uses in traditional medicine, as vegetable to human and as animal feed.

MATERIALS AND METHODS

Plant material: The plant Portulaca oleracea was collected around Samaru Village near Ahmadu Bello University, Zaria, Nigeria in October 2004 and identified by the herbarium unit of the Department of Biological Sciences, Ahmadu Bello University and Zaria, Nigeria. A voucher specimen (No. 2389) has been deposited in the same place.

Preparation and extraction of the plant material: The plant material was dried in shade and grounded to a coarse powder. Fifty grams of the powdered material macerated with 250 mL methanol at room temperature for 24 h. The extract was filtered and dried at 40°C under vacuum. The yield was 14.5% (w/w).

Animals used: Swiss albino mice (17-24 g) of either sex maintained at the animal house of the Department Pharmacology and Clinical Pharmacy, Ahmadu Bello University, Zaria were used for the determination of the LD50. The animals were housed in well-ventilated room at temperature 24±2°C; fed with standard feeds and water ad libitum. The protocol for the study was approved by Ahmadu Bello University Ethics Committee (ABUEC) responsible for the implementation of ethics in animal experimentation.

Acute toxicity: Different doses of the extract were injected intraperitoneally into six groups of four mice each. The number of death was counted at 24 h after treatment. The LD50 values were determined by the methods of Karber; Miller and Tainter and Muench and Reed as modified by Aliu and Nwude (1982).

Histopathology: Tissue section of the liver, kidney, lungs and heart were fixed in 10% buffered formalin for 72 h. The tissues were processed using technicon and sectioned at 5 μm, they were mounted on clean glass slides, dried at room temperature and stained with Haematoxylin and Eosin. This was cover slipped and dried. The slides were studied using Zeiss microscope (Arthur and John, 1978).

RESULTS AND DISCUSSION

The sign and symptoms observed before the death of the animals include micturation, muscle weakness, dypsnoea, sedation and diarrhea, which were all observed to be dose dependent. The increased micturation resulting from increased diuresis observed can be attributed to the presence of the flavonoids and the diarrhoea might be due to the anthraquinones and its derivatives (Leung and Forster, 1996; Ezekwe et al., 1999).

The acute toxicity established the intraperitoneal LD50 of the extract to be1853.5 mg kg-1 by the Miller and Tainter method (Table 1). Probit values of the corrected percentage values are plotted against the logarithms of the dose and the curve is presented in Fig. 1. The LD50 is calculated from slope of the linear equation. Reed and Muench method establish an LD50 of 1871 mg kg-1, (Table 2) and 1875 mg kg-1 was obtained using the Karber method (Table 3). This shows that the methanolic extract of P. oleracea is moderately toxic based on the WHO toxicity rating (Gleason et al., 1969) the plant is expected therefore, to have a high therapeutic index.

On the histopathological studies (Table 4), the plant extract was found to cause congestion of blood vessels and necrosis of renal tubular epithelium and the lungs. Congestion and necrosis of hepatocytes especially around the central vein were observed in the liver. The heart and spleen sections showed no significant histopathological changes.


Table 1: Results for LD50 of methanolic extract of P. oleracea according to miller and Tainter method
Image for - Toxicity Studies on the Methanolic Extract of Portulaca oleracea L. (Fam. Portulacaceae)

Table 2: Results for LD50 of methanolic extract of P. oleracea according to reed and Muench method
Image for - Toxicity Studies on the Methanolic Extract of Portulaca oleracea L. (Fam. Portulacaceae)

Table 3: Results for LD50 of methanolic extract of P. oleracea according to Karber method
Image for - Toxicity Studies on the Methanolic Extract of Portulaca oleracea L. (Fam. Portulacaceae)

Table 4: Results of histopathological observation on some organs of the dead mice
Image for - Toxicity Studies on the Methanolic Extract of Portulaca oleracea L. (Fam. Portulacaceae)

Image for - Toxicity Studies on the Methanolic Extract of Portulaca oleracea L. (Fam. Portulacaceae)
Fig. 1: Log dose-Probit curve according to Miller and Tainted method for the determination of LD 50 of P. oleracea

CONCLUSION

Portulaca oleracea is moderately toxic based on the LD50-values obtained by applying the three methods, according to WHO classification. A further chronic toxicity study is recommended to further ascertain the safety or otherwise of the plant.

REFERENCES

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