Mass spectrometry in the study of molecular complexes between 5‐fluorouracil and catechins

Abstract

Abstract5‐Fluorouracil (5FU) is a widely employed antineoplastic agent that acts as antimetabolite. However, 5FU activity is strongly reduced against a subset of cancer cells called cancer stem cells (CSCs), which are believed to be responsible for chemoresistance and tumour recurrence. It was found that epigallocatechin‐3‐gallate (EGCG), the most abundant catechin present in green tea extract, suppresses CSCs grown in various cancers. This chemosensitizing effect of EGCG was investigated in 5FU‐resistant (5FUR) CRC cells, showing that EGCG enhances 5FU‐induced cytotoxicity. However, the real mechanism of an improved 5FU chemosensitivity in the presence of EGCG was not evaluated. Considering the capability of catechins to form bimolecular noncovalent complexes, in the present study, the interaction of catechins and 5FU was studied by different mass spectrometric approaches. The ESI(+) and ESI(−) spectra of [5FU‐catechin] mixtures were studied, showing the formation of protonated and deprotonated bimolecular complexes, whose nature was confirmed by MS/MS experiments (product and precursor ion scans). To exclude the possible origin of these species as ESI artefacts, a further series of experiments were performed by high‐resolution liquid chromatography–mass spectrometry. By this approach, bimolecular complexes have been detected at retention times different from those of free 5FU and catechins, proving their presence in the original solution. Analogous studies were performed on 5FU‐green tea extract mixtures, showing that 5FU leads to complexes not only with EGCG but also with other catechins. These molecular species, differently to free 5FU drug alone, would in principle possess a new biological activity and could be an explanation of the described activity cited above.

An investigation on [5 fluorouracil and epigallocatechin-3-gallate] complex activity on HT-29 cell death and its stability in gastrointestinal fluid

“…In fact, an ion source temperature of 120°C and a desolvation gas (sheath gas) temperature of 600°C are present and the latter could be responsible for the decomposition of the bimolecular, non-covalent complex. Hence the MS data seems, at first sight, to exclude the formation of the complex, even if previous results obtained by triple quadrupole (QqQ) instrument operating in softer conditions unequivocally proved its formation [29]. Then the complex has to be considered in principle present in the solution of [5FU+EGCG].…”

“…Looking at these findings and considering our previous experience on the formation of bimolecular noncovalent complexes described in the introduction section, in particular on the formation of [5FU+EGCG] complex [29], it was considered of interest to undertake the present investigation on its possible role in the biological activity described for 5FU and EGCG mixtures.…”

“…Considering the previous results related to the detection of [5FU+EGCG] complex in triple quadrupole conditions [29] and the absence of complex identification by qTOF instrument above discussed, a series of experiments were performed by direct infusion of 5FU, EGCG and the mixture of [5FU+EGCG] in the ESI source of a triple quadrupole mass spectrometer (QqQ), operating in positive and negative ion conditions [ESI(+) and in ESI(−) respectively]. Tandem mass spectrometry (MS/MS) experiments were carried out by product ion and precursor ion scans [43] of the ions of interest.…”

“…Considering the capability of catechins to form bimolecular non-covalent complexes, the interaction of catechins and 5FU was recently studied by different mass spectrometric approaches [29]. It was found that 5FU and catechins interact, leading to the formation of non-covalent complexes.…”

Discovery of a New CDK4/6 and PI3K/AKT Multiple Kinase Inhibitor Aminoquinol for the Treatment of Hepatocellular Carcinoma

“…(Bollard et al, 2017;Teo et al, 2017;Wang et al, 2018). 5-Fluorouracil (5-Fu) is a widely employed antineoplastic agent that acts as anti-metabolite (Wang et al, 2018;Moracci et al, 2021). Sorafenib has been used as a first-line drug in clinical practice for patients with advanced liver cancer for more than a decade (Bollard et al, 2017;Kudo 2020).…”