Profiling of phenolic compounds from different apple varieties using comprehensive two-dimensional liquid chromatography

• Comprehensive LC is applied to phenolic compound profiling for the first time.
• Apple procyanidins and other phenolics are simultaneously analyzed in a single run.
• HILIC and RP are combined to increase separation power and identification certainty.
• Different apple varieties are characterized by HILIC × RP-DAD–MS/MS.

An innovative analytical approach based on the use of comprehensive two-dimensional liquid chromatography (LC × LC) is applied to obtain the profiling of phenolic compounds in different apple varieties. The method combines the use of hydrophilic interaction liquid chromatography in the first dimension and a reversed phase separation in the second dimension, as well as the use of diode array and mass spectrometry detection. Using this methodology is possible to obtain in less than 50 min the complete profiling of phenolic compounds in a complex food matrix such as apple. In fact, different flavan-3-ols including procyanidin oligomers with degree of polymerization up to 8, as well as several dihydrochalcones, flavonols and a phenolic acid are separated and tentatively identified in these samples in a single run. Besides, the total phenols and total procyanidins amounts were determined using two in vitro assays. Reinette apples presented the highest content on total phenols (6.46 mg galic acid equiv./g dry matter) whereas Granny Smith apples were the richest on total procyanidins (0.73 mg epicatechin equiv./g dry matter). This work shows the great potential of LC × LC for phenolic compounds profiling in complex food samples.