Methods of depolymerizing lignin and products obtained therefrom. The methods include reacting lignin in a liquid solvent comprising an oxidation catalyst with the solvent being in contact with 02 gas. The solvent can include aprotic polar solvents. The oxidation catalyst can include heterogeneous catalysts. The methods can be used in the oxidative catalytic fractionation of raw biomass to generate soluble aromatic monomers and a solid carbohydrate residue. Depolymerized lignin products include phenolic and benzoquinone monomers, such as p-hydroxybenzoic acid, vanillin, syringaldehyde, vanillic acid, and/or syringic acid.