A compound represented by formula I or II. R1 and R2 are at each occurrence selected from the group consisting of hydrogen, methyl, phenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,4,5-trimethoxyphenyl, 2-hydroxyphenyl, 3-hydroxyphenyl, 4-hydroxyphenyl, 2-fluorophenyl, 2-chlorophenyl, 2-bromophenyl, 3-fluorophenyl, 3-chlorophenyl, 3-bromophenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 2-fluoro-3-methoxyphenyl, 3-methoxy-4-chlorophenyl, 2,4-difluorophenyl, 2,4-dichlorophenyl, 2,4-dibromophenyl, 2-fluoro-4-chlorophenyl, 2-bromo-4-chlorophenyl, 3-fluoro-4-chlorophenyl, 3-bromo-4-chlorophenyl, 3,4-difluorophenyl, 3,4-dichlorophenyl, 3,4-dibromophenyl, 2-chloro-4-fluorophenyl, 2-bromo-4-fluorophenyl, 3-chloro-4-fluorophenyl, 3-bromo-4-fluorophenyl, 2-fluoro-4-bromophenyl, 2-chloro-4-bromobenzene group, 3-fluoro-4-bromophenyl, 3-chloro-4-bromophenyl, 2,3,4-trichlorophenyl, 2-methoxy-4-chlorophenyl, 2-hydroxy-4-chlorophenyl, 2-hydroxy-4-methoxyphenyl, 3-fluoro-4-(4-methylpiperazinyl)phenyl, 4-(N,N-dimethylamino)phenyl, and 3-fluoro-4-(4-morpholinyl)phenyl. R3 and R4 are hydrogen, or R3 and R4 are at each occurrence selected from the group consisting of —CH2CH2COOH, —CH2CH2CH2CH2COOH, —CH2CH═CHCH2COOH, and —CH2CH2CH2CH2CH2CH2CH2COOH; or R3 and R4 are —COR5, and R5 is selected from the group consisting of 3-pyridyl, —CH2CH2COOH, —CH2CH2CH2CH2COOH, —CH2CH═CHCH2COOH, and —CH2CH2CH2CH2CH2CH2CH2COOH.