Introduction

Spondias mombin Linn, commonly known as Hog plum in English language and ‘Ijikara' by the people of southeastern Nigeria, is a medium sized but occasionally large tree. It is widely found in tropical America, Asia and Africa, and has been recently cultivated in commercial quantities in Mexico (Leon and Shaw, 1990). It may be propagated by seeds but is usually grown from stem cuttings. The tree is widely grown for its yellow pleasant pulp-like fruits, or used as live fence posts and for provision of shade. The fruits are popular for eating and the extracted juice is used to prepare ice cream, cool beverages, jam and wine such as ‘Vino de Taperiba' (Morton, 1987). The plant is reported to have multiple therapeutic properties. The bark when steeped in water gives a decoction used by women in rural areas as a vaginal douche, and is also drunk to cure ailments of reproductive system. The decoction of the astringent bark also serves as emetic, a remedy for diarrhea, dysentery, haemorrhoids and also as a treatment for gonorrhoea (Martinez, 2000). The plant leaves have been reported to contain antiviral ellagitannins and caffeoyl esters and antibacterial and molluscicidal phenolic acids (Corthout et al, 1994). The leaves have also been demonstrated to have antihelmintic (Ademola et al, 2005) and abortifacient (Offiah and Anyanwu, 1989) activities.

In traditional medical practice of southern Nigeria, fresh boiled aqueous leaf extract of S. mombin is used to treat dizziness especially after childbirth, while the bark is used to cook for mothers after delivery (Onwuka, 1992). The leaves are commonly fed to pregnant domestic animals to hasten littering or to expel placenta after successful littering (Nzegbule and Meregini, 1999). All these medicinal uses notwithstanding, the plant leaves are among the tropical browse species fed to goats and sheep in Nigeria (Onwuka, 1992).

Given the traditional, medicinal and domestic uses of S. mombin, there is a need for elaborate studies of the physiological and biochemical aspects of the plant. the present communication describes studies of the effects of this ethnic drug source on the serum lipid profile of rabbits.

Materials And Methods

Collection, Identification and Extraction of Plant Materials

Phytochemical Analysis

Experimental Animal Models

Collection of Blood Samples

Lipid Analysis

Statistical Analysis

Results

S. mombin leaf extract was found to contain saponins, alkaloids, flavonoids, phenols and tannins. The administration of the extract generally reduced the serum lipid content of the animals. There was a significant (p<0.05) concentration-dependent decrease in serum total cholesterol (TC), which was more pronounced with administration of higher doses (Table 1). Although, reduction in TC continued as the days of treatment progressed, as from the 8 ^th day there was no significant difference (p>0.05) between the effects of the different doses on TC concentrations.

Figure 1

Table 1: Effect of aqueous extract on the total cholesterol (mg/dl) concentrations of experimental rabbits

Values are mean ± standard deviation. ^* Values are significant (p<0.05) compared to corresponding control values.

There was no significant (p>0.05) reduction in high-density lipoprotein cholesterol (HDL-C) in the treated animals in comparison with the control (Table 2). Similarly, variation in extract dose administration did not significantly (p>0.05) reduce HDL-C in the animals after 12 days of treatment with 250mg/kg and 500mg/kg of extract. On the other hand, treatment for 12 days with 750mg/kg of extract caused a slightly significant (p<0.05) reduction in HDL-C concentrations.

Figure 2

Table 2: Effect of aqueous extract on serum high-density lipoprotein cholesterol (mg/dl) concentrations of experimental rabbits

Triacylglycerol (TG) concentration of the animals administered with the extract was significantly (p<0.05) reduced in comparison with the control. This reduction was found to be significantly (p<0.05) extract-dose dependent (Table 3).

Figure 3

Table 3: Effect of aqueous leaf extract on serum triacylglycerol (mg/dl) concentrations of experimental rabbits

Extracts administration caused significant (p<0.05) decrease in loe-density lipoprotein cholesterol (LDL-C) concentration when it's concentrations in treated animals were compared with those of the control (Table 4). However, there was observed no significant (p>0.05) difference in the effects of varying extract dose administration on LDL-C concentration of treated animals.

Figure 4

Table 4: Effect of aqueous leaf extract on serum low-density lipoprotein cholesterol (mg/dl) concentrations of experimental rabbits

Administration of extract at the different doses did not significantly (p>0.05) reduce atherogenic index of the treated animals in comparison with the controls (Table 5). Similarly, neither duration of treatment nor extract dose variation affected significantly (p>0.05) the atherogenic indexes of the animals.

Figure 5

Table 5: Effect of aqueous extract on the atherogenic indexes of experimental rabbits

Finally, administration of extract did not also cause significant (p>0.05) reductions in free fatty acid (FFA) levels (Table 6). Furthermore, the reductions were non-significantly (p>0.05) dose and duration dependent.

Figure 6

Table 6: Effect of aqueous extract on serum free fatty acids (mg/dl) concentration of experimental rabbits

Discussion

Secondary plant metabolites, such as saponins, alkaloids, phenols, flavonoids and tannins detected in S. mombin extract, exhibit varied biochemical and pharmacological actions in animals and even microorganisms when ingested (Trease and Evans, 1983). Thus, flavonoids, alkaloids and tannins have been associated with antimicrobial effects (Abo et al, 1999). Similarly, many plants containing alkaloids and flavonoids have been shown to have diuretic, antispasmodic, anti-inflammatory and analgesic actions (Owoyele et al,2002). Saponins are known anti-nutritional factors, which reduce the uptake of certain nutrients including glucose and lipids especially cholesterol at the gut through intra-lumenal physicochemical interaction. Hence, saponins have been reported to have hypocholesterolemic effects (Price et al, 1987). The presence of saponin in S. mombin Linn may explain the antilipidemic effect observed in this study.

Results of the present study showed that aqueous leaf extract of S. mombin has serum lipid-lowering effect on the levels of total cholesterol, triacylglycerol and free fatty acids. The observed extract dose- and duration of administration dependent cholesterol lowering effect may be attributed to the gut intra-lumenal interactive effect of saponins. The lowered TC concentration may have contributed to the observed non-significant low serum HDL-C in the animals. About 30% of blood cholesterol is carried in the form of HDL. It is hypothesized that HDL can remove cholesterol from atheroma within arteries and transport it back to the liver for excretion or re-utilization. Thus, high level of HDL-C protects against cardiovascular disease (Kwiterovich, 2000). The observed non-significant change in HDL-C concentration upon administration of extract indicates that, although the extract does not have HDL-C boosting effect, it does not also have significant lowering effect on HDL-C concentration, even at high doses. The observed slight decrease in HDL-C may be due to the effect of over-dose as may useful antilipidemic vegetables like Vernonia amygdalina have been shown to be toxic at high doses (Ojiako and Nwanjo, 2006).

On the other hand, the extract even at the lowest dose used significantly reduced LDL-C concentration. Low-density lipoprotein transports cholesterol to the arteries where they can be retained by artierial proteoglycans, starting the formation of plaques. LDL-C poses a risk for cardiovascular disease when it invades the endothelium and become oxidized, since the oxidized form is more easily retained by the proteoglycans. Thus, increased levels of LDL-C are associated with artherosclerosis heart attack, stroke and peripheral vascular disease (Cromwell and Otvos, 2004).

The import of this LDL-C lowering effect of the extract is that the extract may aid in the prevention or reduction of cardiovascular risk factors. Cholesterol, triacylglycerol and fatty acids are significant and independent risk factors of adverse cardiovascular events (Wierbicki and Mikhailidis, 2002). The non-significant changes in the levels of atherogenic indexes of the extract treated animals may be due to the dependence of the index on the unvarying HDL-C. The non-significant reductions in the atherogenic indexes never-the-less, portend a decreased risk of vascular disease since high atherogenic index has been positively correlated with cardiovascular risk (Igwe et al, 2007).

In conclusion, aqueous leaf extract of S. mombin has a general lipid lowering effect which may be clinically beneficial to individuals at risk of cardiovascular disease because of its observed lipid-lowering potential. Considering the current high prevalence of metabolic diseases and the general availability of the studied plant, the use of the plant in resource-poor economies by an impoverished populace should be strongly promoted.

Acknowledgement