Cytotoxic activity of stigmasteryl esters and products of their thermo-oxidative degradation against drug sensitive and drug resistant human acute lymphoblastic leukemia cells.

Abstract

Phytosterols are mainly known as a cholesterol-lowering factor, although they form oxidation products during food storage and processing. Moreover, phytosterol oxidation products (POP) can be ab- sorbed and found in human serum, so there is the need to investigate their impact on different kinds of cells. Esters of fatty acids (oleic, linoleic and linolenic) with stigmasterol were synthetized and heated at 180°C, for 1–12 hours. The cytotoxic effect on the leukemic cells of unheated stigmasteryl esters and the mixture of compounds after heating was determined using MTT assays. POP were identified using GC-MS. The total number of POP was analysed by SPE fractionation and GC-FID separation. Dimers, trimers and oligomers in non-polar fraction were determined by gel permeation chromatography with refractive index detection. After heating, stigmasterol oxidation products were formed (up to 1.1 mg/g ester). The heating increased the potency of the compounds to reduce cell population and form POPs and oligomers in a time-dependent manner. The cytotoxicity depends on the kind of ester, dose and time. The strongest cytotoxic effect was found after 72 hours of cell treatment. Among the three stigmasteryl esters tested the most cytotoxic effect was caused by stigmasteryl linoleate.