Occurrence of tocopheryl fatty acid esters in vegetables and their non-digestibility by artificial digestion juices

Sample preparation of free sterols from vegetable oils by countercurrent chromatography in co-current mode

Countercurrent chromatography (CCC) is a preparative instrumental method where both the mobile and stationary phases are liquids and which are predominantly used for the isolation of natural products. In this study, we widened the scope of CCC by using it as an instrumental method for the direct enrichment of the free sterol fraction from plant oils to which they contribute with ~ 1%. For the enrichment of sterols in a narrow band, we employed the so-called co-current CCC (ccCCC) mode in which both liquid phases of the solvent system (here: n-hexane/ethanol/methanol/water (34:11:12:2, v/v/v/v)) are moved at different flow rates in the same direction. Different from previous applications of ccCCC, the lower and predominant "stationary" phase (LP_s) was pumped twice as fast as the mobile upper phase (UP_m). This novel reversed ccCCC mode improved the performance but also required a higher demand of LP_s compared to UP_m. Therefore, the exact phase composition of UP_m and LP_s was determined by gas chromatography and Karl Fischer titration. This step enabled the direct preparation of LP_s which considerably reduced the waste of solvents. Internal standards (phenyl-substituted fatty acid alkyl esters) were synthesised and utilised to frame the free sterol fraction. This approach allowed a fractionation of free sterols based on the UV signal and compensated run-to-run variations. The reversed ccCCC method was then applied to the sample preparation of five vegetable oils. In addition to free sterols, free tocochromanols (tocopherols, vitamin E) were also eluted in the same fraction as free sterols.

Free tocopherols and tocotrienols in 82 plant species' oil: Chemotaxonomic relation as demonstrated by PCA and HCA

The tocopherol (T) and tocotrienol (T3) profile were investigated in the present study for four hundred and eighteen plant oil samples, including thirty-one families, eighty-two species, and five cross-species. Fifteen species were dominated by tocotrienols, while sixty-seven - by tocopherols. The mean proportion of γ-T was almost half of the total tocochromanol content (49.3%) in the investigated samples, while α-T constituted to one quarter (25.0%), and the remaining other tocochromanols were present as minor constituents. A strong relationship between the taxonomic plant origin and the presence of the characteristic tocochromanol profile in oils obtained from those plants was noted. This is the first study to demonstrate that not only monocotyledonous, but also dicotyledons families can be rich in tocotrienols. The usefulness of statistical tools - principal component analysis (PCA) and hierarchical cluster analysis (HCA) for plant sample discrimination based on their tocochromanol profile was also shown.

Chemical composition of the lipophilic compounds from the rind and pith of papyrus (Cyperus papyrus L.) stems

Papyrus (Cyperus papyrus L.) is a sedge plant with a high rate of biomass productivity that represents an interesting raw material to produce chemicals, materials and fuels, which are currently still obtained from fossil resources, in the context of a lignocellulosic biorefinery. In this work, the content and chemical composition of the lipids present in papyrus stems were thoroughly studied. For this, the papyrus stems were separated into the rind and the pith. The lipid content accounted for 4.1% in the rind and 4.9% in the pith (based on dry matter). The main compounds identified in both parts of the papyrus stem were hydrocarbons, n-fatty acids, 2-hydroxyfatty acids, alcohols, alkylamides, mono- and diglycerides, steroids (sterols, ketones, hydrocarbons, esters and glycosides), tocopherols, tocopherol esters, phytol, phytol esters, alkyl ferulates, ω-carboxyalkyl ferulates (and their monoglycerides), and acylglycerol glycosides. The rind presented a predominance of n-fatty acids (6790 mg/kg; that represented 28.6% of all identified compounds), steroid compounds (6255 mg/kg; 26.3%), phytol and phytol esters (4985 mg/kg; 21.0%), and isoprenoid hydrocarbons, namely phytadiene and squalene (2660 mg/kg; 11.2%), while the most abundant lipids in the pith were steroids (8600 mg/kg; 44.4% of all identified compounds) and fatty acids (6245 mg/kg; 32.2%). Due to the great diversity and significant abundance of the compounds identified in papyrus, it can be considered as a potential raw material for biorefineries to obtain valuable phytochemicals of interest to various industrial sectors.

Free and Esterified Tocopherols, Tocotrienols and Other Extractable and Non-Extractable Tocochromanol-Related Molecules: Compendium of Knowledge, Future Perspectives and Recommendations for Chromatographic Techniques, Tools, and Approaches Used for Tocochromanol Determination

Free and esterified (bound) tocopherols, tocotrienols and other tocochromanol-related compounds, often referred to "tocols", are lipophilic antioxidants of great importance for health. For instance, α-tocopherol is the only tocochromanol with vitamin E activity, while tocotrienols have a positive impact on health and are proposed in the prevention and therapy of so-called modern diseases. Tocopherols, tocotrienols and plastochromanol-8 are the most well-known tocochromanols; in turn, knowledge about tocodienols, tocomonoenols, and other rare tocochromanol-related compounds is limited due to several challenges in analytical chemistry and/or low concentration in plant material. The presence of free, esterified, and non-extractable tocochromanols in plant material as well as their biological function, which may be of great scientific, agricultural and medicinal importance, is also poorly studied. Due to the lack of modern protocols as well as equipment and tools, for instance, techniques suitable for the efficient and simultaneous chromatographical separation of major and minor tocochromanols, the topic requires attention and new solutions, and/or standardization, and proper terminology. This review discusses the advantages and disadvantages of different chromatographic techniques, tools and approaches used for the separation and detection of different tocochromanols in plant material and foodstuffs. Sources of tocochromanols and procedures for obtaining different tocochromanol analytical standards are also described. Finally, future challenges are discussed and perspective green techniques for tocochromanol determination are proposed along with best practice recommendations. The present manuscript aims to present key aspects and protocols related to tocochromanol determination, correct identification, and the interpretation of obtained results.

Tocopherols and Tocotrienols-Bioactive Dietary Compounds; What Is Certain, What Is Doubt?

Tocopherols and tocotrienols are natural compounds of plant origin, available in the nature. They are supplied in various amounts in a diet, mainly from vegetable oils, some oilseeds, and nuts. The main forms in the diet are α- and γ-tocopherol, due to the highest content in food products. Nevertheless, α-tocopherol is the main form of vitamin E with the highest tissue concentration. The α- forms of both tocopherols and tocotrienols are considered as the most metabolically active. Currently, research results indicate also a greater antioxidant potential of tocotrienols than tocopherols. Moreover, the biological role of vitamin E metabolites have received increasing interest. The aim of this review is to update the knowledge of tocopherol and tocotrienol bioactivity, with a particular focus on their bioavailability, distribution, and metabolism determinants in humans. Almost one hundred years after the start of research on α-tocopherol, its biological properties are still under investigation. For several decades, researchers' interest in the biological importance of other forms of vitamin E has also been growing. Some of the functions, for instance the antioxidant functions of α- and γ-tocopherols, have been confirmed in humans, while others, such as the relationship with metabolic disorders, are still under investigation. Some studies, which analyzed the biological role and mechanisms of tocopherols and tocotrienols over the past few years described new and even unexpected cellular and molecular properties that will be the subject of future research.

Fate of free and bound phytol and tocopherols during fruit ripening of two Capsicum cultivars

Phytol and tocopherols and their fatty acid esters (PFAE and TFAE) are isoprenoid lipid components which can be found for instance in vegetables. Their behavior during maturation of fruits and vegetables could reveal valuable information on their biosynthetic formation and biological function. As pods of the genus Capsicum contain considerable amounts of both PFAE and TFAE, two cultivars (i.e. Capsicum annuum var. Forajido and Capsicum chinense var. Habanero) were grown in a greenhouse project. The date of flowering and fruit formation of each blossom was noted and fruits were harvested in four specific periods which corresponded with different stages of ripening, i.e. unripe, semi-ripe, ripe and overripe. Quantification by means of gas chromatography mass spectrometry and creation of development profiles strongly supported the suggestion that PFAE and TFAE were formed as storage molecules during fruit ripening and parallel degradation of chlorophyll. Additionally, compound-specific carbon isotope ratios (δ¹³C values (‰)) of originally in PFAE and chlorophyll bound phytol ultimately proved that PFAE, besides tocopherols, serve as sink for the cytotoxic phytol moiety released from chlorophyll degradation during fruit ripening. Furthermore, color measurements were successfully implemented to simplify the usually cumbersome separation of chili fruits into different ripening degrees.

Chemical Composition and In Vitro Bioaccessibility of Antioxidant Phytochemicals from Selected Edible Nuts

The ultimate health benefits of peanuts and tree nuts partially depend on the effective gastrointestinal delivery of their phytochemicals. The chemical composition and in vitro bioaccessibility of tocopherols, tocotrienols and phenolic compounds from peanuts and seven tree nuts were evaluated by analytical and chemometric methods. Total fat and dietary fiber (g 100 g-1) ranged from 34.2 (Emory oak acorn) to 72.5 (pink pine nut; PPN) and from 1.2 (PPN) to 22.5 (pistachio). Samples were rich in oleic and linoleic acids (56-87 g 100 g-1 oil). Tocopherols and tocotrienols (mg·kg-1) ranged from 48.1 (peanut) to 156.3 (almond) and 0 (almond, pecan) to 22.1 (PPN) and hydrophilic phenolics from 533 (PPN) to 12,896 (Emory oak acorn); flavonoids and condensed tannins (mg CE.100 g-1) ranged from 142 (white pine nut) to 1833 (Emory oak acorn) and 14 (PPN) to 460 (Emory oak acorn). Three principal components explained 90% of the variance associated with the diversity of antioxidant phytochemicals in samples. In vitro bioaccessibility of tocopherols, tocotrienols, hydrophilic phenolics, flavonoids, and condensed tannins ranged from 11-51%, 16-79%, 25-55%, 0-100%, and 0-94%, respectively. Multiple regression analyses revealed a potential influence of dietary fiber, fats and/or unsaturated fatty acids on phytochemical bioaccessibility, in a structure-specific manner.

Stable Carbon and Nitrogen Isotope Ratios of Red Bell Pepper Samples from Germany, The Netherlands, and Spain

Bell pepper is one of the most cultivated crops in the world. By means of δ¹³C and δ¹⁵N values (‰), red bell peppers from Germany, The Netherlands, and Spain could be distinguished from each other. German fruits cultivated under greenhouse conditions were extremely depleted in ¹³C with δ¹³C values for fatty acids of partly less than -50‰. The strong depletion in ¹³C was in accordance with the use of biomethane-derived CO₂ as growth regulator in the greenhouses. Seasonal variations in the δ¹³C values (‰) of German samples were tentatively assigned to varying CO₂ enrichment during the annual production cycle. δ¹³C values (‰) of Dutch samples also correlated with greenhouse production, whereas Spanish samples most likely originated from open field cultivation. Additionally, the use of color measurement as a tool for presorting the samples was investigated in order to slim the scattering ranges of δ¹³C and δ¹⁵N values (‰) for clearer differentiation.