Development of a fast extraction method and optimization of liquid chromatography–mass spectrometry for the analysis of phenolic compounds in lentil seed coats

• A systematic optimization for LC–MS analysis of polyphenols in lentil seed coats.
• Acid extraction of polyphenols resulted in the breakdown of polymeric compounds.
• Polyphenols were extracted efficiently in 1 h with acetone: H2O (70: 30, v/v).
• A core–shell Kinetex PFP column gave better isomer separation than C18 columns.
• We developed a 30 min LC–MS method that showed differences among three genotypes.

A systematic set of optimization experiments was conducted to design an efficient extraction and analysis protocol for screening six different sub-classes of phenolic compounds in the seed coat of various lentil (Lens culinaris Medik.) genotypes. Different compounds from anthocyanidins, flavan-3-ols, proanthocyanidins, flavanones, flavones, and flavonols sub-classes were first optimized for use as standards for liquid chromatography mass spectrometry (LC–MS) with UV detection. The effect of maceration duration, reconstitution solvent, and extraction solvent were investigated using lentil genotype CDC Maxim. Chromatographic conditions were optimized by examining column separation efficiencies, organic composition, and solvent gradient. The results showed that a 1 h maceration step was sufficient and that non-acidified solvents were more appropriate; a 70:30 acetone: water (v/v) solvent was ultimately selected. Using a Kinetex PFP column, the organic concentration, gradient, and flow rate were optimized to maximize the resolution of phenolic compounds in a short 30-min analysis time. The optimized method was applied to three lentil genotypes with different phenolic compound profiles to provide information of value to breeding programs.