A method of treating tumor including administering to a subject an effective amount of a compound of the following formula: STR1 wherein m is 1-4; and each of A and B, independently, is H, C1-7 alkyl, C2-7 alkenyl, C2-7 alkynyl, (CH2)n CHO, (CH2)o COOH, C1-7 alkoxy, C2-7 alkoxyalkyl, C1-7 hydroxyalkyl, CN, NO2, halogen, CH(OR1)2, CO.R1, NR2 R3 or its acid salt, CO.NR2 R3, CHR1 NR2 R3 or its acid salt, CH=NR2, C CR4, CR1 =CR5 R6, CO.CH=CHR7, CH=CHR8, or COOR9 ; in which each of n and o, independently, is 0-4; R1 is C1-4 alkyl or C1-4 acyl; each of R2 and R3, independently, is H, C1-4 alkyl, or C1-4 hydroxyalkyl; R4 is H, C1-4 alkyl, C2-4 alkenyl, COR2, COOR10, C1-4 hydroxyalkyl or its acid ester or 2-tetrahydropyranyl ether, C1-4 dihydroxyalkyl or its acid ester or 2-tetrahydropyranyl ether, C1-4 halogenated alkyl; OR1, or NHR7 ; each of R5 and R6, independently, is H, CHO, COR1, COOH, COOR9, CN, or halogen; R7 is H, C1-4 alkyl, 2-thienyl, phenyl, mono-substituted phenyl, or di-substituted phenyl; R8 is COOR2, CO.CHO, C1-4 hydroxyalkyl or its acid ester or 2-tetrahydropyranyl ether; and R9 is H, C1-4 alkyl, phenyl, mono-substituted phenyl, di-substituted phenyl, or 2-thienyl.