A metabolite-profiling approach to assess the uptake and metabolism of phenolic compounds from olive leaves in SKBR3 cells by HPLC-ESI-QTOF-MS.

Olive leaves, an easily available natural low-cost material, constitute a source of extracts with significant antitumor activity that inhibits cell proliferation in several breast-cancer-cell models. In this work, a metabolite-profiling approach has been used to assess the uptake and metabolism of phenolic compounds from an olive-leaf extract in the breast-cancer-cell line SKBR3 to evaluate the compound or compounds responsible for the cytotoxic activity. For this, the extract was firstly characterized quantitatively by high-performance liquid chromatography coupled to electrospray ionization-quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS). Then, SKBR3 cells were incubated with 200 µg/mL of the olive-leaf extract at different times (15 min, 1, 2, 24, and 48 h). A metabolite-profiling approach based on HPLC-ESI-QTOF-MS was used to determine the intracellular phenolic compounds, enabling the identification of 16 intact phenolic compounds from the extract and four metabolites derived from these compounds in the cell cytoplasm. The major compounds found within the cells were oleuropein, luteolin-7-O-glucoside and its metabolites luteolin aglycone and methyl-luteolin glucoside, as well as apigenin, and verbascoside. Neither hydroxytyrosol nor any of its metabolites were found within the cells at any incubation time. It is proposed that the major compounds responsible for the cytotoxic activity of the olive-leaf extract in SKBR3 cells are oleuropein and the flavones luteolin and apigenin, since these compounds showed high uptake and their antitumor activity has been previously reported.

Identification of phenolic compounds from pollen extracts using capillary electrophoresis-electrospray time-of-flight mass spectrometry.

In this work, a new, easy and rapid method of analyzing phenolic compounds in pollen extract, based on capillary electrophoresis coupled with electrospray ionization time-of-flight-mass spectrometry (CE-ESI-TOF-MS), has been developed. A systematic investigation of separation parameters has been performed with respect to resolution, sensitivity, analysis time and peak shape. The electrophoretic parameters and electrospray conditions must be optimized to obtain reproducible analyses. Using this method, several important phenolic compounds such as acetin-glucoside, 7-O-methylherbacetin-3-sophoroside, galloyl-glucose, quercetin-3-sophoroside, apigenin-6,8-di-C-glycoside, quercetin-3-rutinoside, genistein-7-O-beta-D: -glucoside, luteolin-7-O-glucoside, apigenin-7-O-glucoside and 2',4',6'-trihydroxy-3'-formyldihydrochalcone have been determined directly from pollen extract. The efficiency, the rapidity, the small amounts of sample required, and the high resolution of CE coupled with the sensitivity, the selectivity, the accurate masses and the true isotopic patterns obtained using TOF-MS point to the potential of this approach for identifying the phenolic compounds present in pollen.