Compounds of formula I: or formula II: or a pharmaceutically acceptable salt of formula I or formula II, wherein: R1 is H, hydroxyl, alkoxy, acyl, alkyl, cycloalkyl, aryl, or heteroaryl; R2 is methyl or haloalkyl; R4 is hydroxyl, carbonyloxy, or carbonyldioxy; and R3 is aliphatic, aryl, aralkyl, or alkylaryl; and R5, R6, R7 and R8 are each individually H, halogen, alkoxy, alkyl, haloalkyl, aryl, nitro, cyano, amino, amido, acyl, carboxyl, substituted carboxyl, or —SO2R10, wherein R10 is H, alkyl, amino or haloalkyl; provided that in formula I, R5 and R7 are not both H or R6 is not H or methoxy; and in formula II that if R4 is carbonyldioxy then R7 is not methoxy.