Separation and isolation of β-sitosterol oxides and their non-mutagenic potential in the Salmonella microsome assay

Oxidation of β-sitosterol and campesterol in sunflower oil upon deep- and pan-frying of French fries

Fried foods, both deep-fried and pan-fried, are enjoyed by people worldwide. Frying is one of the main factors leading to formation of phytosterols (PS) oxidation products (POP) in vegetable oils. The aim of this study was to measure the oxidation of β-sitosterol (24α-ethyl-5-cholesten-3β-ol) and campesterol (24α-methyl-5-cholesten-3β-ol) in commercial sunflower oil (SFO) during deep- and pan-frying of French fries for different periods (30, 60, 120 and 240 min). The total amount of PS in SFO was 4732 μg/g, wherein the major PS were β-sitosterol and campesterol. The results of POP were confirmed by the GC-MS analysis that monitored the formation of oxides during frying. Upon frying, total PS content decreased whereas the highest decrease was measured after 240 min of frying. The oxidative stability (OS) of different sitosterol and campesterol during both frying methods was evaluated. In general, pan frying resulted in more PS oxidation than deep frying. β-Sitosterol oxides predominated while campesterol oxides were formed to a lesser extent. 7-Ketositosterol, followed by 7β-hydroxysitosterol, 5,6-epoxy derivatives and 7α-hydroxysitosterol were the main POP induced during frying. The proportion of 7-keto derivatives decreased during frying while the proportion of 7β-hydroxy derivatives increased. The formation of POP might be a limiting factor for frying in SFO for long periods.

Development and validation of a gas chromatography-mass spectrometry method for determination of sterol oxidation products in edible oils

An efficient GC-MS method for determination of sterol oxidation product profiles in edible oils was established by combination with optimized silylation, and validated using the standards of sitosterol oxidation products.

Novel synthesis strategy for the preparation of individual phytosterol oxides

Sterols (cholesterol and phytosterols) are important structural components of cell membranes and major constituents of lipid metabolism. Research on their oxides, such as the factors affecting oxidation, oxides' structures, and qualitative and quantitative analysis, aroused more attention in this decade. However, the biological roles of individual phytosterol oxides are still unclear because no commercial individual phytosterol oxide standards are available. Different from the traditional chemical synthesis, in the present study, chemical synthesis from a starting phytosterol mixture followed with a semipreparative HPLC separation produced individual oxides. TLC and analytical HPLC were used here to not only monitor the reaction process but also specifically analyze the synthetic intermediates and oxides. The chromatographic results exhibited strict rules and similar characteristics. Finally, for the first time, four individual phytosterol oxides were successfully separated and collected by a semipreparative HPLC system, thus providing a novel strategy for the preparation of individual phytosterol oxides.

Genotoxicity assessment of water soluble fractions of biodiesel and its diesel blends using the Salmonella assay and the in vitro MicroFlow® kit (Litron) assay

The designation of biodiesel as an environmental-friendly alternative to diesel oil has improved its commercialization and use. However, most biodiesel environmental safety studies refer to air pollution and so far there have been very few literature data about its impacts upon other biotic systems, e.g. water, and exposed organisms. Spill simulations in water were carried out with neat diesel and biodiesel and their blends aiming at assessing their genotoxic potentials should there be contaminations of water systems. The water soluble fractions (WSF) from the spill simulations were submitted to solid phase extraction with C-18 cartridge and the extracts obtained were evaluated carrying out genotoxic and mutagenic bioassays [the Salmonella assay and the in vitro MicroFlow® kit (Litron) assay]. Mutagenic and genotoxic effects were observed, respectively, in the Salmonella/microsome preincubation assay and the in vitro MN test carried out with the biodiesel WSF. This interesting result may be related to the presence of pollutants in biodiesel derived from the raw material source used in its production chain. The data showed that care while using biodiesel should be taken to avoid harmful effects on living organisms in cases of water pollution.

Current and new insights on phytosterol oxides in plant sterol-enriched food

Over the past 15 years, plant sterol-enriched foods have faced a great increase in the market, due to the asserted cholesterol-lowering effect of plant sterols. However, owing to their chemical structures, plant sterols can oxidize and produce a wide variety of oxidation products with controversial biological effects. Although oxyphytosterols can derive from dietary sources and endogenous formation, their single contribution should be better defined. The following review provides an overall and critical picture on the current knowledge and future perspectives of plant sterols-enriched food, particularly focused on occurrence of plant sterol oxidation products and their biological effects. The final objective of this overview is to evince the different aspects of plant sterols-enriched food that require further research, for a better understanding of the influence of plant sterols and their oxides on consumers' health.