Comprehensive polyphenol profiling of a strawberry extract (Fragaria × ananassa) by ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry

Abstract

The aim of metabolic untargeted profiling is to detect and identify unknown compounds in a biological matrix to achieve the most comprehensive metabolic coverage. In phytochemical mixtures, however, the complexity of the sample could present significant difficulties in compound identification. In this case, the optimization of both the chromatographic and the mass-spectrometric conditions is supposed to be crucial for the detection and identification of the largest number of compounds. In this work, a systematic investigation of different chromatographic and mass-spectrometric conditions is presented to achieve a comprehensive untargeted profiling of a strawberry extract (Fragaria × ananassa). To fulfill this aim, an ultra-high-pressure liquid chromatography system coupled via an electrospray source to a hybrid quadrupole-Orbitrap mass spectrometer was used. Spectra were acquired in data-dependent mode, and several parameters were investigated to acquire the largest possible number of both mass spectrometry (MS) features and MS mass spectra for unique metabolites. The main classes of polyphenols studied were flavonoids, phenolic acids, dihydrochalcones, ellagitannins, and proanthocyanidins. Method optimization allowed to us identify and tentatively identify 18 and 113 compounds, respectively, among which 74 have never been reported before in strawberries and, to the best of our knowledge, 22 of them have never been reported before. The results show the importance of an extended investigation of the chromatographic and mass-spectrometric method before a complete untargeted profiling of complex phytochemical mixtures.

Impact of elevated carbon dioxide and temperature on strawberry polyphenols

“…The polyphenol profile of strawberries shows that they have a highly diverse composition and La Barbera et al have confirmed or tentatively identified over 130 different individual compounds. The diversity of these compounds must be taken into consideration in fruit nutrition as their biological and pharmacological activities are specific to their chemical structure .…”

“…A range of other phenolic compounds such as phenolic acids (hydroxycinnamic acids, p-coumaroyl, ferulic acid derivatives), stilbenes (resveratrol), and coumarins (p-coumaric acid), which are beneficial to human nutrition and health, have also been identified in strawberry fruits. 9,[11][12][13] However, the strawberry polyphenol profile can vary widely qualitatively and quantitatively as it is affected by various factors, including genotype, environmental factors, and their interactions. [14][15][16][17][18][19][20][21] The genetic makeup of strawberries is the most critical contributory factor in the variability of the nutritional quality of fruits in terms of total polyphenol content (TPC), total antioxidant content (TAC) and levels of individual polyphenols; however, growing conditions or environmental factors also play a significant role in determining the nutritional value of strawberries.…”

Evaluation of column length and particle size effect on the untargeted profiling of a phytochemical mixture by using UHPLC coupled to high‐resolution mass spectrometry

“…The chromatographic method for systems (a) and (b) was chosen based on the work of La Barbera et al Phase B gradient was the following: 5–15% in 10 min, 15–35% in 15 min, 35–50% in 5 min, at 40°C (still air option), with ACN/HCOOH (99.9:0.1, v/v) as phase B and H 2 O/HCOOH (99.9:0.1, v/v) as phase A. The same conditions were kept for systems (c) and (d) but with the following gradient: phase B 5–15% in 20 min, 15–35% in 30 min, and 35–50% in 10 min.…”

“…The coelution of isomeric metabolites makes them indistinguishable and could generate ionization suppression of the less abundant compounds. Therefore, optimizing the chromatographic conditions in an untargeted analysis could be crucial for maximizing the number of detected and consequently identified compounds .…”

“…The feasibility of the qualitative and quantitative analyses was evaluated by a deep investigation on peak shapes, retention times, and peak areas repeatability. Moreover, to provide more insight into the performance of the column systems, nontargeted profiling was carried out on strawberry extracts, due to their well‐known complexity in isomeric antioxidant compounds content . The chromatographic systems were evaluated based on the number of detected features and, finally, on the putative identification of some classes of polyphenol compounds.…”