Finally, the µF/mnESI displayed a data structure comparable to the AF/ESI workflow both via unsupervised multivariate data analysis (PCA) and supervised (OPLS-DA) methods. The µF/mnESI method provided a broader coverage of lipids contributing to class separation, as illustrated in Fig. with an increase in oxidized TGs and a decrease in SISE after exposure to combination therapy. Sitosterols are plant-derived sterols which are currently evaluated as nutraceuticals in clinical applications . Their esterified forms were not yet reported in mammalian in vitro systems. Fetal calf serum (FCS) used in cell culture preparation could be a probable source of its substrates, as it has been reported that FCS composition can greatly influence cell culture experimental outcomes . Monitoring the metabolic products of sitosterols can be of importance considering the growing clinical interest for this class of compounds. Extension of coverage to oxidized TG species with µF/mnESI is also of importance, as it indicated an otherwise hardly detectable contribution of reactive oxygen species (ROS)-dependent processes to the overall effect of the cell treatment in this study. For instance, tubacin, dasatinib and erlotinib, included in the treatment combination, are known to activate apoptotic pathways in malignant cells via increased ROS generation . Therefore, the presented µF/mnESI approach is indispensable for studying oxidative effects induced by drugs on lipid metabolism in cell cultures, with the aim of further characterizating the mode of action of multidrug combination therapies.