Separation and characterization of phenolic compounds from dry-blanched peanut skins by liquid chromatography–electrospray ionization mass spectrometry

• Published in: Journal of Chromatography A Vol. 1356; pp. 64 - 81
• Main Authors: Ma, Yuanyuan, Kosińska-Cagnazzo, Agnieszka, Kerr, William L., Amarowicz, Ryszard, Swanson, Ruthann B., Pegg, Ronald B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 22.08.2014; Elsevier
• Subjects: Arachis - chemistry; Biflavonoids; Biological and medical sciences; Chromatography, High Pressure Liquid - methods; Chromatography, Liquid; Chromatography, Reverse-Phase; Dry-blanched peanut skins; ESI–MSn; Esters; Flavonoids - chemistry; Flavonoids - isolation & purification; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; HILIC; Mass Spectrometry; Nuts - chemistry; Phenols - chemistry; Phenols - isolation & purification; Plant Extracts - chemistry; Plant Extracts - isolation & purification; Proanthocyanidins (PACs); RP-HPLC; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; Proanthocyanidins (PACs); RP-HPLC; Dry-blanched peanut skins; ESI–MSn; Biflavonoids; HILIC; Tandem mass spectrometry; Phenolic acid; HPLC chromatography; Oligomer; Flavonoid; Electrospray; Polyphenol; Peel; Proanthocyanidin; Quantitative analysis; Peanut; Catechin; Fruit; Coupled method; Hydrophilic Interaction Liquid chromatography; ESI-MS; Stilbene derivatives; Reversed phase chromatography; Phenols; Skin; ESI–MS(n)
• ISSN: 0021-9673; 1873-3778
• DOI: 10.1016/j.chroma.2014.06.027

•A large variety of phenolic compounds were identified in dry-blanched peanut skins (PS) by HPLC–MSn.•PS contain significantly more PACs compared to free phenolic compounds.•p-Coumaroyl derivatives account for roughly 3/4 of the non-PAC phenolics found in PS.•HILIC with fluorescent detection revealed the profile of the PACs found in PS.•Our findings reported here greatly enrich the phenolics database of PS. A large variety of phenolic compounds, including phenolic acids (hydroxybenzoic acids, hydroxycinnamic acids, and their esters), stilbenes (trans-resveratrol and trans-piceatannol), flavan-3-ols (e.g., (−)-epicatechin, (+)-catechin, and their polymers {the proanthocyanidins, PACs}), other flavonoids (e.g., isoflavones, flavanols, and flavones, etc.) and biflavonoids (e.g., morelloflavone), were identified in dry-blanched peanut skins (PS) by this study. High-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI–MSn) was applied to separate and identify the phenolic constituents. Reversed-phase HPLC was employed to separate free phenolic compounds as well as PAC monomers, dimers, and trimers. PACs with a degree of polymerization (DP) of >4 were chromatographed via hydrophilic interaction liquid chromatography (HILIC). Tentative identification of the separated phenolics was based solely on molecular ions and MSn fragmentation patterns acquired by ESI–MS in the negative-ion mode. The connection sequence of PAC oligomers (DP <5) could be deduced mainly through characteristic quinone methide (QM) cleavage ions. When the DP reached 6, only a proportion of the flavan-3-ols could be ascertained in the PACs because of the extremely complicated fragmentation patterns involved. The identification of free phenolic acids, stilbenes, and flavonoids was achieved by authentic commercial standards and also by published literature data. Quantification was performed based on peak areas of the UV (free phenolic compounds) or fluorescence (PACs) signals from the HPLC chromatograms and calibration curves of commercial standards. Overall, PS contain significantly more PACs compared to free phenolic compounds.