Abstract: The toxicity of powdered Stachytarpheta jamaicensis (L.) Vahl. leaves, known for treating different ailments such as diabetes, hypertension and bacterial infections in some Nigerian communities, was investigated in rats. Twenty Wister rats (male and female) were fed with different graded mixtures of Pfizer feed mash and the leaf powder. The animals were weighed and divided into four groups of three treatment groups and one control group with each group consisting of five rats. The rats were administered different concentrations of powdered S. jamaicensis leaves mixed with different amount of feed mash.i.e. 75, 50 and 5 g of S. jamaicensis was mixed with 25, 50 and 75 g of normal feed mash. The control was fed only with feed mash all through the period of experiment. The results obtained showed slight variation on the physical signs/body appearance of the animals and mild histopathlogic 1esions such as congestion, fatty changes and necrosis in selective tissues such as the liver, blood vessels, kidney, lung and testis but the brain, eyes, intestines (small and large) and heart tissues were essentially normal. S. jamaicensis seem to cause mild non-dose dependent systemic toxicity in some specific tissues.
INTRODUCTION
Herbs have been used by people of diverse cultural backgrounds through history. It was and still is an integral part of the development of modern civilization. One of the earliest records of the use of herbal medicine is that of Chaulmoorgia oil which was known to be effective in the treatment of leprosy (Sofowora, 1982). About 75% of the population of developing countries depend on medicals of plant origin (Ampofo and Johnson-Romaud, 1978). Natural medical products especially those of plant origin represent indispensable tools for the development of new drug both in the developing and industrialized nations (Bonati, 1993).
The use of different plants parts, mostly their extract either as decoctions, infusions, oral administration etc. have been used as popular medicine in several countries in the underdeveloped, developing and developed ones as an alternative treatment for various diseases. Some of these plants that exhibit medicinal properties have been known to help in stabilizing different internal organs in animals, while others have had side effects on the organs probably due to the varying amount or quantity of toxic matter present in such plants.
Toxicity testing in animals is carried out on a new drug to identify potential hazard. It helps in determining the upper limits of administration (Sofowora, 1993). If the toxic effect of a drug is low then, there is a chance of possible introduction of such drug for therapeutic use.
The Plant Stachytarpheta jamaicensis (Verbanaceae), commonly called Bastard vervain or Brazilian tea, is an erect or straggling perennial herb about 60-90 cm high. The leaves often covered with flowers, gives it a bluish green color. The leaves are opposite and whorled; ovate or oblong, elliptic about 4-11 cm long and 2-4.5 cm wide, rounded to broadly acute at the apex, widely toothed at the margins, smooth on both surfaces with short petioles.
Several medicinal values of this have been reported in works of several authors (Dragendorff, 1998; Asprey and Thornton, 1955; Feng et al., 1962; Simpson, 1962; Subramanian, 1974; Wong, 1976; Ayensu, 1978; Evans and Raj, 1988; Robinson et al., 1990; Gill, 1992; Cruz, 1995; Schapoval et al., 1998; Chariandy et al., 1999; Antoun et al., 1999; Ramos et al., 2001). In this study, the dose related effect of powdered leaves of S. jamaicensis on animal tissues was investigated for toxicity while also keeping the animal on supplementary feeds with feed mash with a view to rationalize the need to freely or cautiously use this plant or its active components in effecting remedy to ailments.
MATERIALS AND METHODS
The leaves of Stachytarpheta jamaicensis were collected around the premises of the University of Benin, Benin City, Edo State, Nigeria in October, 2004 and was identified by Mr. Henry Akinnibosun using A Handbook on West African Weeds (Akobundu and Agyakwa, 1988) and authenticated by Prof. MacDonald Idu, both of Botany Department, University of Benin, Benin City. Nigeria.
| Table 1: | Physical characteristics and food intake observations of experimental rats (n = 5 per group) |
| +++ = Good, ++ = Average, + = Fair | |
| Table 2: | Average weight changes in rats following treatments with various doses of combinations of feed (n=5 per group) |
| Mean±SE (standard error) | |
| Table 3: | Histological observation of various tissue sections |
The herbarium specimen (No. B103) has been deposited at Botany Department, University of Benin, Benin City. Nigeria. The leaves were washed and air dried, cleaned off debris and kept in the oven to dry at 40°C for 18 h. The leaves were plucked off the dried branches and pounded in a mortar to obtain the powdered form. Three kilogram of the powdered leaves was weighed and stored in a moisture free airtight container for use.
Twenty wister rats were randomly sampled and kept one per cage. They were allowed to acclimatize for two weeks, during which they were fed with pfizer feed mash and water ad libitum before commencement of the experiment. After acclimatization, the rats were divided into three treatment groups and one control group of five rats each. The duration of experiment was six weeks, conducted from October 16 to November 30; 2004. The control group received only feed mash throughout the period. The treatment groups were fed with mash only for the first three weeks and thereafter received mash/leaf powder mixture in the following ratio weight/weight: 75/25, 50/50 and 25/75, respectively.
Behavioral signs and general appearance such as agility, food consumption, water consumption, loss of hairs, eye changes were observed. Body weight was measured once a week during the course of treatment.
Methods for sacrificing, processing of tissues, fixation and staining, were adopted following methods outlined by Idu et al. (2002) and Ataman et al. (2002).
RESULTS
Physical characteristics of experimental rats: From Table 1 agility was observed to be slightly reduced in T2 group for the 2nd week which was regained in the 3rd week. There was noticeable reduction of agility in T3 in the 2nd and 3rd weeks. Those of T1 and Control groups were normal. Food intake for TI group and control group were normal. The feeding pattern of rats in T2 group was slightly reduced but later returned to normal in the 2nd week. Amongst these rats, some had reduced intake while others had increase in food intake. T3 group was noticed to have some rats which rarely ate and where, they did, it was minimal. There was however no hair loss observed in all the rats and the eye color remained normal (Table 1).
The percentage weight gain of the rats in Control, T1, T2 and T3, groups, respectively decreased in that order as one observed during the period. A possible explanation for this is that the higher the concentration of the leaf powder in the mixture, the lesser the likelihood of quantity consumed; thus resulting in reduced weight gain (Table 1 and 2).
Histopathology: Sections of the liver, heart, kidney, lungs, brain, small intestine and large intestine of the various rats were studied and the results summarized in Table 3.
| Fig. 1: | Lung tissue sections showing (a) Control, (b) T1 with normal cells, (c) T2 with areas of congested blood vessels, (d) T3 with normal cells and areas of congested blood vessels |
| Fig. 2: | Kidney tissue sections showing (a) Control, (b) T1 with normal cells, (c) T2 with normal cells and (d) T3 with areas of necrosis |
| Fig. 3: | Heart tissue sections showing (a) Control, (b) T1 with normal cells (c) T2 with normal cells and (d) T3 with normal cells |
| Fig. 4: | Testis tissue sections showing (a) Control, (b) T1 showing areas of congested blood vessels and (c) T2 showing normal cells |
| Fig. 5: | Large intestine tissue sections showing (a) Control, (b) T1 with normal cells (c) T2 with normal cells and (d) T3 with normal cells |
| Fig. 6: | Small intestine tissue sections showing (a) Control, (b) T1 with normal cells (c) T2 with normal cells and (d) T3 with normal cells |
| Fig. 7: | Brain tissue sections showing (a) Control, (b) T1 with normal cells (c) T2 with normal cells and (d) T3 with normal cells |
| Fig. 8: | Liver tissue sections showing (a) Control, (b) T3 with areas of fatty changes |
| Fig. 9: | Spleen tissue section showing (a) Control treatment with normal cells |
From Fig. 1-9, the lung tissue sections showed areas of congested blood vessels in T2 treatments and areas of congested blood vessels in interspersed with normal cells in the T3 treatment group. T1 group showed normal cells. The kidney tissue section of Control, T1 and T2 treatments had normal cells and T3 showed areas of necrosis. The heart tissue section of the Control, T1, T2 and T3 treatments had normal cells. The testicular tissue section of the Control and T2 treatments had normal cells while T1 treatment had areas of congested blood vessels. The liver tissue revealed areas of fatty changes in the T3 treatment group. The small intestine, large intestine, spleen and brain tissues had no observable pathology in all the treatment groups.
DISCUSSION
During the period of experiment, four rats especially from group T3 were noticed to have loss of agility and also exhibited neck twisting. They looked malnourished. This may be due to low food intake as the mixture of the plants with feed mash significantly altered the original mash taste. Increased concentrations of active compounds in plant extracts are not always beneficial and can even promote adverse biological effect (Pepato et al., 2001). Rats in groups T2 and T3 had some slight changes in agility during the 3rd and 4th weeks. Rats in T3 lost some weights, probably due to the high dose of powdered leaves given to them. This is in line with the studies carried out by Reddy et al. (1996), where high dose of TNT (Tri-nitro-benzene) was given which significantly reduced the weights of the experimental rats. Similarly, in the experiment carried out by Ataman et al. (2002), they observed reduced weight and agility in experimental rats fed with different concentrations of the plant extract of Cycas revoluta other than the normal feed mash. Reduced agility is an indication of disease condition (Brigid et al., 1980). There was no hair loss observed in the rats and the eyes were all normal. Water intake was also normal in the Control, TI and T2 groups but reduced in T3 group.
The result of the histopathologic studies of various tissue sections, showed some significant pathologic difference in some organs, namely: lungs, kidney, testis and liver (Fig. 1, 2, 4 and 8). Congested blood vessels and areas of hemorrhage were noticed in the Liver of T1 rat. The kidney section of T3 showed areas of necrosis. Congested blood vessels were observed in the lungs of T1 and T3. Fatty changes of the liver was present in T3 while the Testis of T1 had congested blood vessels. There were areas of necrosis in the kidney of T3 group. This is similar to studies by Reddy et al. (1996), where susceptible organs like the kidney was affected when fed with a high concentration of TNT which caused necrosis.
The animals appear to have more pathological lesions in the groups with the lowest and highest concentrations of the leaf powder, i.e. T1 and T3 compared to the intermediate group T2. It is possible that the absolute total leaf powder consumption is higher in the group T1 with the lowest concentration than the intermediate group T2 since the former appeared to have consumed more of the feed than the later. This may be responsible for the lesions in some of the tissues that were not affected in the intermediate T2 group. A similar explanation may hold for the T3 group, which obviously consumed the feed containing the highest dose of the leaf powder.
It can be concluded from these results that while S. jamaicensis may be useful in the treatment of certain disease conditions, systemic toxicity is also likely. It would appear that the plant’s toxicity affects some tissues more than others, thus suggesting specific tissue sensitivity of S. jamaicensis as opposed to dose related toxicity often associated with therapeutic agents. This remark is plausible as some tissues such as the liver cells, ducts and blood vessels as well as tissues of the kidney, testis and lungs seems to be more susceptible to damage. Caution should therefore be exercised in the therapeutic use of this plant.
Further research is needed to isolate the active ingredients and the possible toxicants that may be present in this plant.