Profiling of Phytosterols, Tocopherols and Tocotrienols in Selected Seed Oils from Botswana by GC–MS and HPLC

The phytosterol, tocopherol, and tocotrienol profiles for mkukubuyo, Sterculia africana, manketti, Ricinodendron rautanenni, mokolwane, Hyphaene petersiana, morama, Tylosema esculentum, and moretologa-kgomo, Ximenia caffra, seed oils from Botswana have been determined. Normal-phase HPLC analysis of the unsaponifiable matter showed that among the selected oils, the most abundant tocopherol and tocotrienol were γ-tocopherol (2232.99 μg/g) and γ-tocotrienol (246.19 μg/g), detected in manketti and mkukubuyo, respectively. Mokolwane oil, however, contained the largest total tocotrienol (258.47 μg/g). Total tocol contents found in manketti, mokolwane, mkukubuyo, morama, and moretologa-kgomo oils were 2238.60, 262.40, 246.20, 199.10, and 128.0 μg/g, respectively. GC–MS determination of the relative percentage composition of phytosterols showed 4-desmethylsterols as the most abundant phytosterols in the oils, by occurring up to 90% in moretologa-kgomo, mkukubuyo, and manketti seed oils, with β-sitosterol being the most abundant. Mokolwane seed oil contained the largest percentage composition of 4,4-dimethylsterols (45.93%). Besides 4-desmethylsterols (75%), morama oil also contained significant amounts of 4,4-dimethylsterols and 4-monomethylsterols (15.72% total). GC–MS determination of the absolute amounts of 4-desmethylsterols, after SPE fractionation of the unsaponifiable matter, confirmed that β-sitosterol was the most abundant phytosterol in the test seed oils, with manketti seed oil being the richest source (1326.74 μg/g). The analysis showed total 4-desmethylsterols content as 1617.41, 1291.88, 861.47, 149.15, and 109.11 μg/g for manketti, mokolwane, mkukubuyo, morama, and moretologa-kgomo seed oils, respectively.     

NMR,GC–MS and ESI-FTICR-MS Profiling of Fatty Acids and Triacylglycerols in Some Botswana Seed Oils

In the search for non-traditional seed oils, physicochemical parameters, fatty acid (FA) and triacylglycerol (TAG) profiles for five Botswana seed oils, obtained by Soxhlet extraction, were determined. GC–MS and ¹H-NMR analyses showed the FA profiles for mkukubuyo, Sterculia africana, and manketti, Ricinodendron rautanenii, seed oils dominated by linoleic and oleic acids, 26.1, 16.7 and 51.9, 24.4%, respectively, with S. africana containing significant amounts of cyclic FAs (19.9%). Mokolwane, Hyphaene petersiana, seed oil was typically lauric; 12:0 and 14:0 acids were 25.9 and 13.4%, respectively. Morama, Tylosema esculentum, seed oil resembled olive oil; 18:1 (47.3%) and 18:2 (23.4%) acids dominated. Moretologa-kgomo, Ximenia caffra, seed oil had 45.8% of 18:1 FA, plus significant amounts of very long chain FAs: 26:1 (5.8%), 28:1 (13.9%), 30:1 (3.9%), and acetylenic acids, 9a-18:1 (1.5%) and 9a, 11t-18:2 (16.0%). TAG classes and regiochemistry were determined with ESI-FTICR-MS, and ¹³C-NMR spectra, respectively. Morama showed seven major TAG classes with C54:4 and C54:3 dominating; mokolwane had 16 major classes with C32:0, C38:0 and C42:2 dominating; manketti had 11 major classes with C54:7, C54:6 and C54:4 dominating; mkukubuyo had 12 major classes with C52:4, C52:3 and C54:4 dominating; moretologa-kgomo had 30 major TAG classes with C64:5, C64:3 and C62:3 dominating. Saturated FAs were generally distributed over the sn-1(3) position for morama, manketti, and moretologa-kgomo but at the sn-2 position for mokolwane and mkukubuyo. These findings indicate that morama and manketti seed oils can be developed for food uses, whilst moretologa-kgomo and mkukubuyo seed oils only for nonfood uses.