The present invention provides for a method to deconstruct a biomass: the method comprising: (a) introducing a solvent comprising a polyamine, or a mixture of polyamines, to a biomass to dissolve at least part of solid biomass in the solvent, wherein the polyamine is a Brønsted or Lewis base, and/or the polyamine is a hydrogen bond donor and/or acceptor; (b) optionally introducing an enzyme and/or a microbe to the solubilized biomass mixture such that the enzyme and/or microbe produces a sugar from the solubilized biomass mixture; (c) optionally separating the sugar from the solubilized biomass mixture; and (d) optionally separating the lignan from the solubilized biomass mixture.