Identification and quantification of soluble and insoluble-bound phenolics in lentil hulls using HPLC-ESI-MS/MS and their antioxidant potential

The identification and quantification of soluble- and insoluble-bound phenolics in lentil hulls were studied using HPLC-DAD-ESI-MSn and their antioxidant potential determined using DPPH radical scavenging ability (DRSA), reducing power (RP), and hydroxyl radical scavenging ability (HRSA) assays to test their electron and hydrogen donating abilities. A number of soluble phenolics such as phenolic acids, flavonoids, and proanthocyanidins were found, which lead to the remarkable antioxidant potential as reflected in DRSA, RP, and HRSA. Meanwhile, insoluble-bound phenolics displayed a relatively lower number of peaks and contents than their corresponding soluble phenolics, leading to a lower antioxidant potential than that of soluble phenolics. Moreover, dihydrokaempferol dimer and carboxylated kaempferol diglucoside were identified for the first time in the insoluble-bound form in lentils. This study offers important data for the identification of phenolic compounds derived from lentils and their antioxidant potential.