The present invention relates to compositions and methods for reversing advanced glycosylation end product-mediated cross-linking and protein aging. Accordingly, compositions are described which comprise thiazolium compounds substituted with heterocyclic groups which are capable of reversing the formation of advanced glycosylation end product cross-links. Both industrial and therapeutic applications for the invention are disclosed, as food spoilage and animal protein aging can be treated. Such compounds have particular application in the treatment of protein aging such as is responsible for the complications of aging and diabetes.