Fatty acid composition of certain oil seeds from Nigeria.
Seeds have nutritive and calorific values which make them necessary item in diets. They are also good sources of edible oils and fats, which are essential nutrients (Odoemelam, 2005). Vegetable oils provide energy and essential linoleic and linolenic acids that are responsible for growth (Fasina et al., 2006). Advances in nutrition research has led to awareness of beneficial and harmful effects of various dietary fats and oils (Dunford, 2001).
Seeds of A. danielli K. Schum are used as a traditional food spice among the Edo and Niger delta people of Nigeria, and also as an anti-inflammatory agent by rubbing of the alcohol and petrol extracts on the allergic and eczematous swelling. A. hypogeae (L.) is a leguminous plant that is mainly grown for its seeds. They are eaten raw, roasted and can be made into a paste used in soups and stew. Glycine max (L.) Merr, popularly known as soybean, is a legume that is increasingly consumed for economical and nutritional reasons. In Nigeria, it is usually roasted, dehulled, grounded and used as additives in making infant cereal and soy milk; they can also be made into paste and used in soups and stew. The palm kernel (Elaeis guineensis var. tenera) is taken from the oil palm; it is surrounded by an edible reddish oily palm. It can be eaten raw or with roasted or cooked maize. P. guineense Thonn. ex Schumach., is a seed that is not commonly eaten in Nigeria; it is closely by related to cubeb pepper, black pepper and long pepper. T. africana Decne. ex Trec., seeds are aromatic and have a flavour much like groundnut. They are eaten raw, roasted, boiled or fried more usually to stews.
The present study was conducted to compare the fatty acid composition of different oils extracted from different seeds that are available in Nigeria, in order to establish a similarity/difference between them and also to determine their potential and hence their possible usage for edible or industrial purposes. There are literature reports on various works that have been carried out on some of these seeds (Ajayi, 2008; Onyeike and Acheru, 2002; Garcia et al., 1998; Oderinde and Ajayi, 1998; Kindu et al., 1987); however, there is no report on the comparative study of the fatty acids of these seed oils.
Materials and Methods
Plant materials and sample collection. The family, scientific, local, english names and abbreviations of the seeds, whose oil extracts are being examined in this study are given in Table 1. These seeds were purchased from local markets in Ibadan, Oyo State, Nigeria. The seeds were identified in the herbarium unit of the Botany department, university of Ibadan, Ibadan, Nigeria, where vouchers of each specimen were already deposited. These seeds were chosen out of interest.
Sample preparation and extraction. The seeds were deshelled manually by cracking to remove the kernels. The kernels were then ground to powder in a hammer mill and stored in air tight sample bottle in a refrigerator (4[degrees]C) until needed for analysis. Seed oils were extracted with n-hexane for 8 h using a Soxhlet extractor. The solvent was removed completely and the oils obtained were used for this study. All chemicals used were supplied by British Drug House (BDH).
Fatty acid analysis. Fatty acid analysis of the seed oils was carried out at the Mass Spectrometry Laboratory, University of Sao Paulo, Ribeirao Preto, Brazil. The methyl ester of the raw oil was prepared according to Idouraine et al. (1996) with some slight modifications. Oil-solvent mixture was evaporated to dryness under nitrogen and then transesterified with [H.sub.2]S[O.sub.4] in the presence of methanol for 2 h at 7[degrees]C. To the resulting fatty acid methyl ester was added 40 mL of water after which the organics were extracted with petroleum ether (40-60[degrees]C) and then dried under nitrogen. The fatty acid methyl esters were redissolved in hexane and analysed in a gas chromatograph (Shimadzu[TM] GC-17A) coupled to mass spectrometer (Shimadzu GCMS-QP5000[TM]), under the following conditions: injector temperature: 250[degrees]C; interface temperature: 270[degrees]C; oven temperature 80[degrees]C 1600 increasing to 160[degrees]C and to 240[degrees]C at 2[degrees]C per 0.5 min; column pressure: 70 KPa, split ratio: 1:50. The column used was the DB-wax 250 (30 m x 0.25 mm from J & W Scientific). The internal standards used were heptadecanoico acid (C17: 0) and the methyl ester of tricosanoico acid (C23: 0) (from Supelco[TM]). To identify the peaks, fatty acid component FAME Mix 37 standard (Supelco[TM]) was used from which the dilutions were made and used to construct the calibration curve in 6, 8 and 10 [micro]g/[micro]L F. It was not possible to detect any fatty acid at concentration below 6 [micro]g/[micro]L.
Results and Discussion
Fatty acid composition of the investigated oils is presented in Table 2. Nine fatty acids have been identified in six oil samples; these are lauric, myristic, palmitic, palmtolenic, stearic, oleic, linoleic, linolenic and arachidonic acids. Palmitic acid was the main saturated component in all the seed oils ranging from A. hypogeae (9.80%) to P. guinesis (26.00%). Even though E. guineensis kernel oil contains palmitic acid (10.70%), it has C12::0 acid (44.90%) as its main fatty acid. Three of the oils contain palmitolenic acid; this ranged from A. danielli (1.20%) to E. guineensis (22.00%). All the oils with the exception of A. danielli (7.50%) and E. guineensis (3.30%) contain linoleic acid in high amount in the range of 23.10% (A. hypogeal) to 34.10% (T. africana) with G. max, having the highest percentage that is 56.40%. Studies on human subjects using diets rich in linoleic acid showed that, in the groups provided with higher amounts of soybean oil (50% linoleic acid content), the mortality rate due to coronary artery decreases significantly (Younis et al., 2000). Ajayi (2009) reports oleic and linoleic acids as the main fatty acids in some seed oils from Nigeria. Sanchez-Manchado et al. (2004) also reports the range of 16.10 [+ or -] 3.31% to 69.11 [+ or -] 9.01% as the polyunsaturated fatty acids (PUFA) contents of some processed edible seaweeds studied.
Most vegetable oils are very good sources of linoleic acid but only very few oils contribute significant amount of linolenic acid in the diet (Longvah et al., 2000). Among the oils examined, A. danielli, G max, P. guineense and T. africana were found to contain linolenic acid ranging from 1.20% for A. danielli to 21.60% for P. guinesis; this is nutritionally significant. The consumption of Perilla oil which contains 57% linolenic acid has been reported in literature to improve learning ability, retinal function and suppression of carcinogenesis, metastasis, thrombosis and allergy (Longvah et al., 2000). The consumption of P. guineense, if the oil is non-toxic, may probably has the same effect that Perilla oil has. A. danielli, G max, P. guineense and T. africana may be considered for highest nutritional significance because of the presence of linolenic acid. Two of the oils; A. danielli and P. guineense contain arachidonic acid. Sanchez-Machado et al. (2004) also reports the presence of arachidonic acid in seaweeds. Generally, the percentage level of unsaturation in the oils is high except for E. guineensis kernel oil; it varied between 62.80% in T. africana and 86.70% in A. hypogeal. The percentage unsaturated fatty acids reported for three of the oils in this study, mainly A. hypogeal, A. danielli and G. max is higher than the one reported in literature for T. occidentalis (Ajayi et al., 2004).
Oleic, linoleic, monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), unsaturated fatty acid (UFA), saturated fatty acid (SAFA) oleic/linoleic, MUFA/PUFA, SAFA/UFA contents of the seed oils are presented in Table 3. The saturated/unsaturated ratio of the E. guineensis kernel oil is 4.32; while, it is less than 1 in all the other oils. This suggests that all the examined oils (except E. guineensis kernel oil) could probably be suitable as edible oil. The MUFA/PUFA ratio of three of the oils is greater than 1; this shows that half of the oils contain more of PUFA than MUFA. Half of the oils also have their oleic to linoleic acid ratio to be greater than 1. This is of great nutritional value since polyunsaturated fatty acids and their derivatives are important essential nutritive additives in mammal, especially in humans (Stransky et al., 2005; Kamal-Eldin and Yanishlieva, 2002; Ziboh et al., 2002).
All the studied oils (except E. guineensis kernel) are highly unsaturated with some of them containing two of the essential fatty acids. The relatively high level of PUFA in the oil extracts (apart from E. guineensis kernel) may make them healthy. However, further work needs to be carried out on some of these oils to determine their toxicity.
The corresponding author is grateful to Third World Academy of Science (TWAS), Italy, for the award of Associateship fellowship to make it possible for this work to be carried out in the Mass Spectrometry Laboratory, University of Sao Paulo, Ribeirao Preto, Brazil. The Department of Chemistry, University of Ibadan, Ibadan, Nigeria is acknowledged for making its facilities available.
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(received December 7, 2012; revised May 16, 2013; accepted June 27, 2013)
Ibironke Adetolu Ajayi (a) *, Julius Sergio Marchini (b), Jose Ernesto Dos-Santos (c) and Julia Keiko Sakamoto Hotta (c)
(a) Industrial Chemistry Unit, Chemistry Department, Faculty of Science, University of Ibadan, Nigeria
(b) Mass Spectrometry Laboratory, Brazil
(c) Laboratoris de Nutricao do Hospital das Clinicas de Riberao Preto, Brazil
* Author for correspondence; E-mail: email@example.com
Table 1. Scientific family, english and local names of the plants investigated Scientific name Family English name Aframomum danielli K. Schum Zangiberaceae Alligator pepper Arachidis hypogeae L. Fabaceae Groundnut Glycine max. (L.) Merr Fabaceae Soybean Piper guineense Thonn. Piperaceae West African pepper ex Schumach. Treculia africana Decne. Moraceae Achi ex Trec. Elaeis guineensis var. Palmae Palm kernel tenera Scientific name Local name Abbreviation Aframomum danielli K. Schum Atare aja AD Arachidis hypogeae L. Epa AH Glycine max. (L.) Merr Ewa soya GM Piper guineense Thonn. Kale, masoro PG ex Schumach. Treculia africana Decne. Ukpo TA ex Trec. Elaeis guineensis var. Ekuro EG tenera Table 2. Fatty acid composition (%) (a) of the seed oils Fatty acid composition A. danielli A. hypogeae G max [C.sub.12:0] -- -- -- [C.sub.14:0] 1.20 -- -- [C.sub.16:0] 21.50 9.80 10.70 [C.sub.16:1] 1.10 - - [C.sub.18:0] 2.70 3.50 3.50 [C.sub.18:1] 63.40 63.60 20.70 [C.sub.18:2] 7.50 23.10 56.40 [C.sub.18:3] 1.20 -- 8.60 [C.sub.20:4] 1.40 -- -- Fatty acid composition P. guineense T. africana E. guineensis [C.sub.12:0] -- -- 44.90 [C.sub.14:0] 4.50 0.20 22.00 [C.sub.16:0] 26.00 20.60 10.70 [C.sub.16:1] 0.80 1.20 -- [C.sub.18:0] 4.20 16.50 3.60 [C.sub.18:1] 9.90 26.20 15.50 [C.sub.18:2] 31.00 34.10 3.30 [C.sub.18:3] 21.60 1.30 -- [C.sub.20:4] 1.80 -- -- (a) = percentage by weight of total fatty acid identified as FAME. Table 3. Oleic, linoleic, MUFA (a), PUFA (b), UFA (c), SAFA (d), oleic/linoleic, MUFA/PUFA, SAFA/UFA contents of the seed oils Parameters A. danielli A. hypogeae G max P guineense MUFA (a) 64.50 63.60 20.70 10.70 PUFA (b) 10.10 23.10 65.00 54.40 UFA (c) 74.60 86.70 85.70 65.10 SAFA (d) 25.40 13.30 14.20 34.70 Oleic/Linoleic 8.45 2.75 0.37 0.32 MUFA/PUFA 6.39 2.75 0.32 0.20 SAFA/UFA 0.34 0.15 0.17 0.53 Parameters T. africana E. guineensis MUFA (a) 27.40 15.50 PUFA (b) 35.40 3.30 UFA (c) 62.80 18.80 SAFA (d) 37.30 81.20 Oleic/Linoleic 0.77 4.70 MUFA/PUFA 0.77 4.70 SAFA/UFA 0.59 4.32 (a) = monounsatnrated fatty acids; (b) = polyunsaturated fatty acids; (c) = unsaturated fatty acids; (d) = saturated fatty acids.
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|Author:||Ajayi, Ibironke Adetolu; Marchini, Julius Sergio; Dos-Santos, Jose Ernesto; Hotta, Julia Keiko Sakam|
|Publication:||Pakistan Journal of Scientific and Industrial Research Series B: Biological Sciences|
|Date:||Nov 1, 2014|
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