Patent ID: 8053461

Claim:
A compound represented by the following general formula (I): wherein R 1 to R 8 may have a hydrogen atom, a halogen atom, a hydroxy group, a C1-C 6 alkyl group, a C2-C8 alkenyl group, a C1-C6 alkylcarbonyl group or —COOR 9 as a substituent, wherein R 9 represents a hydrogen atom, a C1-C6 alkyl group or a C2-C8alkenyl group; and X represents a sulfur atom, an oxygen atom or NR 10 , or a pharmaceutically acceptable salt thereof, wherein R 10 represents a hydrogen atom, a halogen atom, a hydroxy group, a C1-C6 alkyl group, a C2-C8 alkenyl group or a C1-C6 alkoxy group.