A comprehensive profiling of free, conjugated and bound phenolics and lipophilic antioxidants in red and green lentil processing by-products

A systemic approach was taken in profiling the hydrophilic and lipophilic antioxidants in lentil hulls using a combination of HPLC, LC-ESI-MS2 and GC techniques. A total of 37 phenolics were tentatively identified in the hydrophilic fractions, while four carotenoids and three tocopherols were found in the lipophilic fraction. Results showed that in addition to the high free extractable phenolics, phenolic compounds in conjugated and bound forms also exist in similar amounts. Information on conjugated and bound phenolics are particularly important as these forms of phenolics often go unnoticed by chromatographic profiling of extractables. All phenolic, carotenoid and tocopherol fractions contributed to antioxidant activities. Information about bioactives from lentil hulls, specifically conjugated and bound phenolics are reported here for the first time. The comprehensive profiling of these bioactives lays a good foundation for further assessment of the value-added uses of lentil hulls which are by-products of pulse processing.