Lipid Lowering Effect Of Aqueous Leaf Extract Of Spondias Mombin Linn
Abstract
The effect of aqueous leaf extract of Spondias mombin Linn on serum lipid profile of rabbits was studied. Preliminary phytochemical analysis was also carried out on the extract. Forty-eight female rabbits, randomly distributed into 4 groups of 12 rabbits each, were orally administered with the extract twice daily for 12 days. The groups I-III animals were administered with the extract at 250mg/kg, 500mg/kg and 750mg/kg body weights respectively, while the remaining group served as the control. The serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-C), atherogenic index and free fatty acid (FFA) levels were determined from blood samples collected on the 0th, 4th, 8th and 12th days of extract administration. The results showed that extract administration significantly (p<0.05) reduced serum TC, TG and LDL-C concentrations. The administration of the leaf extract on the other hand, did not significantly (p<0.05) reduce serum HDL-C in groups I and II animals. FFA concentration and the atherogenic indexes of the animals had no significant differences between tests and control. These findings may be of clinical importance to individuals at risk of cardiovascular disease.
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
Apparently healthy fresh leaves of S. mombin were obtained from the yam barn of the National Root Crop Reasearch Institute, Umudike, Nigeria. They were authenticated by a plant taxonomist at the Department of Plant Science and Biotechnology, Imo State University, Owerri, Nigeria. The leaves were dried to constant weight at 60 ° C in a laboratory oven. They were later ground into fine powder with the aid of a clean dry electric grinder (ED-5 Arthur Thomas, USA). A 100g portion of the ground leaves was soaked in 100 ml of water for 12 hours, filtered and then exhaustively extracted with the aid of soxhlet extractor (Gallenkamp, England). The solvent in the extract was then distilled off in a distillatory and evaporated to dryness at 40 ° C. The solid extract was placed in a sterile container, labeled and stored at 4 ° C in a refrigerator from where portions were taken for the different studies (Ojiako and Nwanjo, 2006).
Phytochemical Analysis
Phytochemical analysis for the presence of alkaloids, tannins, saponins, flavonoids and cardiac and cyanogenic glycosides was carried out as described by Harborne (1973), and Trease and Evans (1983).
Experimental Animal Models
Forty-eight healthy female rabbits, 8-12 months old with mean weight 1.50 ± 0.52kg obtained locally from Owerri, Imo State, were randomly distributed into 4 groups (I-IV) of 12 rabbits each. They were housed separately and fed ad libitum water and growers'mash (Guinea Feed Nigeria) and allowed for a week to acclimatize to laboratory conditions. Group I animals were then administered 250mg extract, group II animals 500mg and group III animals 750mg per kg body weight respectively, while the group IV animals (controls) were not administered extract at all. The extract doses were orally administered (by the use of an intubator) twice, morning and evening, daily for a total period of 12 days.
Collection of Blood Samples
On the 0 th , and 2 hours after the second extract administration on the 4 th , 8 th and 12 th days, three animals were randomly selected from each group and 10ml of blood samples collected by cardiac puncture from each animal after mild anesthesia with chloroform in accordance with University Ethical Committee regulations. Serum was separated from the blood after clotting and centrifugation, and used for lipid analysis.
Lipid Analysis
Serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triacylglycerol (TG) were determined by enzymatic methods as described by Stein (1987), and Walmsley and White (1994). The concentration of free fatty acids (FFA) was estimated by standard titration method using 0.1N NaOH and phenolphthalein indicator (Nwanjo, 2004). The low-density lipoprotein cholesterol (LDL-C) was calculated using the Friedewald et al (1972) formula, while atherogenic index (AI) was determined as described by Igwe et al (2007).
Statistical Analysis
Student's t-test and one-way analysis of variance (ANOVA) were used to compare the various data obtained. Values for p<0.05 were considered statistically significant.
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.
Table 1: Effect of S. mombin 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.
Table 2: Effect of S. mombin 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).
Table 3: Effect of S. mombin 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.
Table 4: Effect of S. mombin 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.
Table 5: Effect of S. mombin 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.
Table 6: Effect of S. mombin 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
The authors are grateful to the management of the Federal University of Technology, Owerri, Nigeria for partly sponsoring this research effort.