PROBLEM TO BE SOLVED: To provide a decomposer (cleaving agent) excellent in an action of decomposing (action of cleaving) "AGEs" which is a product resulted from Maillard reaction.SOLUTION: A cleaving agent of the invention contains free gallic acid as an active ingredient. An example of a route for obtaining the free gallic acid from a plant is utilizing the gallic acid contained in a residue (low-temperature decompression dry distillation residue R) when subjecting the plant to dry-distillation under low temperature and decompression conditions, or an extract from the low-temperature decompression dry distillation residue R by a solvent (residue extractable matter E).
