The Analysis of Phenolic Compounds in Walnut Husk and Pellicle by UPLC-Q-Orbitrap HRMS and HPLC

Abstract

Husk and pellicle as the agri-food waste in the walnut-product industry are in soaring demand because of their rich polyphenol content. This study investigated the differential compounds related to walnut polyphenol between husk and pellicle during fruit development stage. By using ultra-high performance liquid chromatography-quadrupole-orbitrap (UHPLC-Q-Orbitrap), a total of 110 bioactive components, including hydrolysable tannins, flavonoids, phenolic acids and quinones, were tentatively identified, 33 of which were different between husk and pellicle. The trend of dynamic content of 16 polyphenols was clarified during walnut development stage by high-performance liquid chromatography (HPLC). This is the first time to comprehensive identification of phenolic compounds in walnut husk and pellicle, and our results indicated that the pellicle is a rich resource of polyphenols. The dynamic trend of some polyphenols was consistent with total phenols. The comprehensive characterization of walnut polyphenol and quantification of main phenolic compounds will be beneficial for understanding the potential application value of walnut and for exploiting its metabolism pathway.

Thinned Nectarines, an Agro-Food Waste with Antidiabetic Potential: HPLC-HESI-MS/MS Phenolic Characterization and In Vitro Evaluation of Their Beneficial Activities

“…Compound 3 showed a [M-H] − ion at m / z 169 and two fragment ions at m / z 141 [M-H-CO] − and m / z 125 [M-H-CO 2 ] − . According to the literature data, this compound was identified as gallic acid [ 26 ]. Compound 4 produced a [M-H] − ion at m / z 343 and a base peak ion at m / z 297, corresponding to the loss of water and CO.…”

Phenolic Compounds: Classification, Chemistry, and Updated Techniques of Analysis and Synthesis

“…Other techniques for analysis of phenolic compounds include capillary electrophoresis (CE) and micellar electro-kinetic chromatography. [22] Recent methods of analysis include ultra-high performance liquid chromatography (UHPLC) [23], ultra-high performance liquid chromatography-quadrupoleorbitrap (UHPLC-Q-Orbitrap) [24], high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS /MS) [25], liquid chromatography coupled with electrospray-ionization triple quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS) and high-performance liquid chromatography-photo diode array (HPLC-PDA) [26], ESI-Ms/MS [27].…”

By-Products of Walnut (Juglans regia) as a Source of Bioactive Compounds for the Formulation of Nutraceuticals and Functional Foods

“…In this sense, several studies reported concentrations of the three most abundant phenolic compounds (juglone, syringic acid and ellagic acid) up to 20 times higher in the skin, compared to the seed [8]. In addition, it is reported that the concentration of phenolic compounds increases gradually from the fruiting stage to the mature stage, reporting TPC and TFC values of 52.05-279.3 mg GAE/g DW and 8.95 mg RE/g FW, respectively [5,25]. As can be seen, the presence of non-flavonoid-type phenolic compounds stands out [25].…”

“…In addition, it is reported that the concentration of phenolic compounds increases gradually from the fruiting stage to the mature stage, reporting TPC and TFC values of 52.05-279.3 mg GAE/g DW and 8.95 mg RE/g FW, respectively [5,25]. As can be seen, the presence of non-flavonoid-type phenolic compounds stands out [25]. Reports stated that most of the compounds present in the walnut skin belong to hydrolyzable tannins, such as digalloyl-glucose, ellagic acid galloyl pentose or galloyl methylgalloyl dexoyhexoside isomer.…”