Qualitative screening of phenolic compounds in olive leaf extracts by hyphenated liquid chromatography and preliminary evaluation of cytotoxic activity against human breast cancer cells

Abstract

In this work, high-performance liquid chromatography (HPLC) coupled to electrospray time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap multiple-stage tandem mass spectrometry (ESI-IT-MS(2)) has been applied to screen phenolic compounds in olive leaf extracts. The use of a small particle size C18 column (1.8 micro) provided great resolution and made separation of a lot of isomers possible. The structural characterization was based on accurate mass data obtained by ESI-TOF-MS, and the nature of fragmentation ions were further confirmed by ESI-IT-MS(2) when possible. In addition, we employed tetrazolium salt (MTT)-based assays to assess the effects of olive leaf extracts on the growth of human tumor-derived cells. Upon this approach, we achieved an accurate profile of olive leaf phenolics along with the identification of several important isomers of secoiridoids and flavonoids. This will allow a better understanding of the complete composition of olive-leaf-bioactive compounds as well as their involvement in Olea europaea L. biochemical pathways. Importantly, olive leaf extracts exhibited dose-dependent inhibitory effects on the metabolic status (cell viability) of three breast cancer models in vitro. Since the tumoricidal activity of the extracts should be mainly attributed to the identified olive leaf phenolics, these findings warrant further investigation at the structure-function molecular level to definitely establish the anticancer value of these phytochemicals.

Olive Leaf Extracts Are a Natural Source of Advanced Glycation End Product Inhibitors

“…The later-eluting peak was identified as the isomeric secologanoside, which elutes after oleoside under reverse-phase conditions. 14 The MS of the peaks arising at 30.6 min (Peak O5) and 34.6 min (Peak O8) displayed a precursor ion at m/z 555; the MS 2 spectrum obtained by fragmentation of this ion presented the following m/z values: 537, 393, and 323, described in literature for 10-hydroxy oleuropein and maybe one of its isomers.…”

“…For the remaining compounds for which no standards were available, identification was based on accurate mass measurements of the pseudomolecular [M-H] -ions and their fragmentation pattern as documented in the literature. 13,14 The total ion current (TIC) chromatograms of MOLE and AOLE are presented in Figure 1. Data obtained from the ESI-MS n analysis of the extracts are summarized in Table 1.…”

A review: benefit and bioactive properties of olive (Olea europaea L.) leaves

“…Several studies have shown that olive leaf extract exhibits a large spectrum of in vitro and in vivo properties, including antioxidant activity [85,86], radio-protective effects [85], anti-proliferative effect on leukemia cells by inducing apoptosis [39,57,87,88], cytotoxic activity against human breast cancer cells [47,89], anti-HIV virus effect [90], antifungal activity [91], gastroprotective activities [92], attenuation of diabetic neuropathic pain [93] and amelioration of gentamicin nephrotoxicity [94]. Several biological properties such as antioxidant, anti-atherosclerotic, hypoglycemic and cardioprotective effects of olive leaves have been reviewed in the literature [76,82].…”

“…Hydroxytyrosol and tyrosol are described as the main representatives of the simple phenolic compounds in olive leaves and in olives [12,[40][41][42][43][44][45][46][47][48].…”

Systematic bottom-up approach for flavonoid derivative screening in plant material using liquid chromatography high-resolution mass spectrometry

“…Based on these findings, increasing research interest has been focused on the deeper understanding of the mechanisms of action of these compounds. For these purposes, however, wide-scope flavonoid profiling methods are required that can provide comprehensive information regarding the various forms of flavonoid compounds in the sample [6][7][8].…”