In the present study, the physicochemical properties, fatty acid composition of Afzelia africana seed oil were determined and also effect of the oil-based diet on growth performance and plasma lipid profile were monitored using twenty Wistar albino rats allocated into two groups of ten rats each. The control group was fed with soybean-based diet while Afzelia africana oil-based diet was fed to the test group ad libitum for 28 days. Results showed the acid, saponification, iodine, and peroxide values of the oil to be 3.30 ± 0.27 mg/KOH/g oil, 124.54 ± 0.79 mg/KOH/g oil, 11.17 ± 0.39 g/100 g, and 10.01 ± 0.53 meq/g respectively. Also, linoleic (53%) and oleic acids (21.34%) were found to be the predominant unsaturated fatty acids present, while the predominant saturated fatty acid present is Palmitic acid (14.78%). The body weight of the experimental rats maintained on diet formulated with Afzelia africana seed oil was reduced compared to the rats fed with control diet. The plasma concentration of triglycerides and high density lipoprotein was not significantly different (p < 0.05) in the two groups while the total cholesterol and low density lipoprotein concentration significantly decreased in the test group fed Afzelia africana oil-based diet. The decline in plasma total cholesterol levels suggests good quality of the oil. The various parameters investigated reveal the potentials of Afzelia africana seed oil and could serve as a good diet supplement.
Afzelia africana plants are mostly cultivated in the Savannah, fringing forest and the drier parts of the forest regions of Africa. The tree is a widespread species with abroad rather open crown and massive branches (most readily recognized by the conspicuous hard blackish fruits), up to 30.5 m high and a girth up to 3 m. It belongs to the family leguminosae and sub-family caesalpinaceae [
The seeds of Afzelia africana used in this research were purchased at Mgbidi, Agwu local government in Enugu State, Nigeria. The seeds were processed using the traditional method [
The Afzelia oil was extracted using the soxhlet extraction procedure [
The acid, saponification, peroxide value and iodine values of the various oil samples were determined by the official AOCS Peroxide Value (PV) method Cd 8 - 53 [
A fat solution of 20 g of Afzelia oil was dissolved in 100 ml of chloroform. 10 ml of the oil solution was pipetted into a stopper bottle and 25 ml of iodine monochloride was added. The stopper bottle was shaken thoroughly and placed in the dark for an hour. A blank solution was prepared with the oil solution replaced with 10 ml of water. After an hour, the stopper bottles were rinsed with about 50 ml of water and 10 ml of potassium iodide solution was added. The resulting solution was titrated with standard thiosulphate. When the solution became pale straw, 1 ml of starch solution was added and the titration continued until blue colouration formed with the starch solution disappeared. The titre values for the test and blank were used to calculate the iodine value.
Iodine Value = ( Blank − Test ) × 6.35
10 g of Afzelia oil was weighed into a beaker. 50 ml of fat solvent was pipetted into the oil. 1 ml of phenolphthalein solution was added and mixed thoroughly. The solution was titrated with 0.1 M KOH until faint pink colour persisted for 20 seconds. The titration was done in duplicate and the acid value was calculated as follows:
Acid Value = titre value × 5.6 10 g ( weight of sample )
5 g of Afzelia oil was weighed into a conical flask. 50 ml 0.5 M of alcoholic KOH was added to the oil. A blank was prepared by dispensing 50 ml of 0.5 M alcoholic KOH with a blank solution into another conical flask. A reflux condenser was connected to each flask and was boiled for an hour. When the flask and condenser cooled, the inside of the condenser was rinsed with little distilled water and was removed. 1 ml of phenolphthalein indicator was added into each flask and titrated against 0.5 M HCl until pink color disappeared. The titre value was taken and the saponification value was calculated thus:
Saponification Value ( mg / g ) = Blank titre value − Sample titre value × 28.05 weight of sample
5 g of Afzelia oil was weighed into clean dry boiling tube. 1 g of powdered potassium iodide and 2 ml of solvent mix was added. The boiling tube was transferred into a water bath containing boiling water and left there to boil vigorously for 30 seconds. The content after 30 seconds of boiling was transferred into a conical flask containing 20 ml of 5% KI solution. The resulting solution was titrated with 0.1 M Na2S2O3 solution until its yellow colour almost disappeared. 0.5 ml of starch solution was added and shaken vigorously after which the titration continued until its blue colouration disappeared. The blank was set up without the oil sample at the same time. The titre value was taken and peroxide value was calculated using the formula below:
Peroxide Value ( mmol peroxide / kg sample ) = Titre value × Molarity of Na 2 S 2 O 3 weight of sample
Twenty (20) male weaning Wistar albino rats were obtained from the animal house, Department of Biochemistry, University of Ilorin, Kwara state, Nigeria. The animals had an initial weight ranging from 40 - 55 g and were kept under standard environmental conditions and were acclimatized for four (4) days. They were fed grower’s mash and clean water ad libitum for the period of acclimatization before the introduction of formulated diet for 28 days.
Soybean oil was used for the control diet formulation. Other constituents includes corn-starch, casilan (protein source), sugar, vitamin-mineral mix and rice bran (fiber) were weighed and mixed together thoroughly by adding little quantity of water after which it was molded into pellets and sun-dried.
Afzelia africana seed oil served as the test ingredient was used to replace soybean oil while maintaining other similar constituents as the control diet.
The experimental diets for the control and test groups were formulated as shown in
Ingredients | Control | Test |
---|---|---|
Corn-starch (carbohydrate) | 560 | 560 |
Casilan (protein source) | 200 | 200 |
Vitamin-mineral mix | 50 | 50 |
Sucrose Cellulose (rice bran) Afzelia africana seed oil Soybean oil | 100 40 - 50 | 100 40 50 - |
After the experimental animals were subjected to acclimatization for four (4) days, they were randomly sorted into one control group and a test group of ten (10) rats each.
§ Control group; fed soybean oil-based diet.
§ Test group; fed Afzelia africana oil-based diet.
After 28 days of experimental feeding, the experimental rats were anaesthetized with chloroform and quickly dissected. Blood was collected via cardiac puncture into lithium-heparin bottles. The blood samples collected were centrifuged at 2500 rpm for 10 minutes and the plasma was separated and was stored in a freezer at 4˚C until required for analysis.
Plasma total cholesterol, HDL cholesterol, and triglycerides were measured on the Hitachi 911 automated analyzer using reagent kits supplied by Roche Diagnostics (Laval, QC, Canada). The precision performance of these assays was within the manufacturer’s specifications. LDL cholesterol was calculated by the Friedewald equation [
Cholesterol was determined after enzymatic hydrolysis and oxidation. The indicator 4-aminoantipyrine was formed from hydrogen peroxide and 4-aminoanti- pyrine in the presence of phenol and peroxidase [
Concentration of Cholesterol ( mmol / l ) = Absorbance of sample Absorbance of standard × Concentration of standard
Serum triglyceride levels were determined after enzymatic hydrolysis with lipases. The indicator is a quinoneimine formed from hydrogen peroxide, 4-aminoph enazone and 4-chlorophenol under the catalytic influence of peroxidase. R1b was reconstituted with 15 ml of R1a to form the working reagent. 1 ml of the working reagent was pipetted in labelled tubes of blank, standard and samples. 10 µl of the standard solution and 10 µl of the samples were pipetted into the standard and samples test tubes respectively. All the test tubes were incubated at 37˚C for five minutes after which the absorbance of the standard and the samples were read against the blank at wave length 546 nm using a spectrophotometer [
Concentration of Triglycerides ( mmol / l ) = Absorbance of sample Absorbance of standard × Concentration of standard
Low density lipoprotein (LDL and VLDL) and chylomicrons fractions were precipitated quantitatively by the addition of phosphotungstic acid in the presence of magnesium ions. After centrifugation, the cholesterol concentration in the HDL fraction which remains in the supernatant was determined. 500 µl of R1 was dispensed into test tubes labelled blank, standard and samples. 200 µl of standard cholesterol and 200 µl of sample plasma were pipetted into the standard and samples test tubes respectively. The tubes were centrifuged at 2500 rpm for five minutes. After centrifugation, 200 µl of the supernatant were dispensed into another set of labelled tubes accordingly after which 2 ml of cholesterol reagent was added. They were incubated for ten minutes at 37˚C [
The absorbance of the sample and standard were determined against the blank at 546 nm using a spectrophotometer.
Concentration of HDL in sample ( mmol / l ) = Absorbance of sample Absorbance of standard × Concentration of standard
The amount of LDL-cholesterol was calculated using the results of a standard lipid profile which consist of total cholesterol, high density lipoprotein and triglycerides [
Low density lipoprotein ( mmol / l ) = cholesterol − ( triglycerides 2 − HDL )
Data obtained were subjected to Duncan’s Multiple Range Test [
The physicochemical properties of Afzelia africana seed oil are shown in
The acid value in mg/KOH/g for Afzelia africana seed oil was 3.30 and this value relates with the values of 3.0, 2.5, for sunflower and coconut oil respectively used as edible and industrial oil [
Saponification values also represent the molecular weight of oil [
Iodine value indicates the drying quality of oil. Dry oil shows higher iodine value [
Peroxide value is a common method used to measure lipid oxidation, and is suitable for measuring peroxide formation in the early stages of oxidation [
The percentage fatty acid composition of Afzelia africana seed oil shown in
The fatty acid profile of fats and oils has a large bearing on their quality. The fatty acid profile affects the shelf-life, flavor and the stability of the oil. From the results obtained, it is observable that Afzelia africana seed oil is a good source of essential fatty acids. Behenic acid is a cholesterol-raising saturated fatty acid in humans [
Parameters | Results |
---|---|
Acid value (mg/KOH/g) | 3.30 ± 0.27 |
Saponification value (mg/KOH/g) | 124.54 ± 0.79 |
Iodine value (g/100 g) | 11.17 ± 0.39 |
Peroxide value (meq/g) | 10.10 ± 0.53 |
Data are mean ± standard deviation of two determinations.
Fatty acids | Afzelia africana oil (%) |
---|---|
Saturated fatty acids Palmitic acid (C16:0) Stearic acid (C18:0) Arachidic acid (C20:0) Behenic acid (C22:0) | 14.78 5.21 0.55 0.40 |
Monounsaturated fatty acids Palmitoleic acid (C16:1) Oleic acid (C18:1) | 1.29 21.34 |
Polyunsaturated fatty acids Linoleic acid (C18:2) Linolenic acid (C18:3) | 53.46 2.97 |
Rats fed a diet of 20% palmitic acid and 80% carbohydrate for extended periods showed alterations in central nervous system control of insulin secretion, and suppression of the body’s natural appetite-suppressing signals for leptin and insulin (the key hormones involved in weight regulation) [
Linoleic acid (53.46%) and linolenic acid (2.97%) are polyunsaturated fatty acids that possess favorable nutritional implications and health benefits, such as regulating blood cholesterol levels, lowering elevated blood pressure and beneficial physiological effects in the prevention of coronary heart disease and cancer [
High ratio polyunsaturated/saturated fatty acids are regarded favorably in the reduction of the serum cholesterol and atherosclerosis and the prevention of heart diseases [
Growth performance of albino rats fed Afzelia africana-based diets
The mean body weights of the rats fed Afzelia Africana seed oil-based diet are shown in
According to the results, the test group has significant decreased (p < 0.05) compared to the control group. Feed gain ratio also known as feed conversion rate or feed conversion efficiency (FCE), feed conversion ratio (FCR) is a measure of an animal’s efficiency in converting feed mass into increases of mass gained by the animal. A low FCR is a good indication of a high quality feed [
The result of the plasma lipid profile of animals fed Afzelia africana oil-based diet is presented in
Control rats (A) | Test rats (B) | |
---|---|---|
Final weight (g) | 113.49 ± 4.07a | 102.98 ± 9.4b |
Initial weight (g) | 50.76 ± 6.2a | 52.91 ± 6.8a |
Weight gain (g) | 62.73 | 50.07 |
Feed intake per day (g) | 70.77 ± 33.9a | 69.62 ± 37.5a |
Results are expressed as mean ± SD (n = 10); values for the test in the same row for each parameter with superscript different from the control are significantly different at p < 0.05.
Parameters | Control (A) | Test (B) |
---|---|---|
Total cholesterol (mmol/l) | 3.4 ± 0.62a | 2.0 ± 0.29b |
Triglycerides (mmol/L) | 1.2 ± 0.63a | 0.84 ± 0.15a |
High density lipoprotein (mmol/l) | 1.24 ± 0.55a | 0.88 ± 0.05a |
Low density lipoprotein (mmol/l) | 1.61 ± 0.42a | 0.64 ± 0.14b |
LDL/HDL TC/HDL | 1.29 2.74 | 0.73 2.27 |
Results are expressed as mean ± SD; values for the test in the same row for each parameter with superscript different from the control are significantly different at p < 0.05.
It reveals that there is no significant difference in the values of triacylglycerol and HDL-C both in the test and control group while LDL-C and total cholesterol had a significant difference in the test and control group. HDL-C transports cholesterol from peripheral tissues to the liver for elimination [
Polyunsaturated fats stimulate the catabolic rate of LDL-cholesterol, thus resulting in the reduction of serum LDL-cholesterol [
Triglycerides (TG) which function as blood lipid helps enable the bi-directional transference of adipose fat and blood glucose from the liver. There was slight significant difference between the test group (0.84 mmol/l) and control group (1.2 mmol/l). This is an indication that Afzelia africana oil does not increase blood triglycerides. Plasma total cholesterol (TC) of the test group is lower than the control group. It has been previously shown that constituents of soybean oil, such as α-linoleic acid, are capable of reducing cholesterol in hypercholesterolemic patients [
This study recommends Afzelia africana seed oil as a good source of unsaturated fatty acids and as such, dietary supplementation and consumption of Afzelia africana seed oil could be beneficial to human health.
No competing financial interests exist.
Ajiboye, I.O., Ajayi, O.B., Akomolafe, S.F. and Adelaja, O.O. (2018) Assessment of Physicochemical Properties, Fatty Acid Composition of Afzelia africana Seed Oil and the Effect of Its Oil-Based Diet on Body Weight and Plasma Lipid Profile of Albino Rats. Food and Nutrition Sciences, 9, 983-996. https://doi.org/10.4236/fns.2018.98072