sentence: These included several classes of inhibitors such as salicylidene acylhydrazides , benzimidazoles , 2,2 ′ - thiobis - ( 4-methylphenol ) , ( - ) - hopeaphenol , acylated hydrazones of various salicylaldehydes , monoanionic squaric acids , α - ketocarboxylic acids , and sulfonamides .