The present invention relates to a compound of formula (I), or a pharmaceutically acceptable salt thereof, wherein Z is OR1 or NR1R2 wherein each of R1 and R2 is independently H, or a hydrocarbyl group; X is an alkylene, alkenylene, or alkynylene group, each of which may be optionally substituted by one or more substituents selected from alkyl, COOH, CO2-alkyl, alkenyl, CN, NH2, hydroxy, halo, alkoxy, CF3 and nitro; Y is a polar functional group selected from OH, NO2, CN, COR3, COOR3, NR3R4, CONR3R4, SO3H, SO2—R3, SO2NR3R4 and CF3, where each of R3 and R4 is independently H or a hydrocarbyl group; A is an aryl or heteroaryl group, each of which may be optionally substituted; and B is (CH2)n where n is 0, 1, 2, 3, 4 or 5; with the proviso that: (i) when A is phenyl, n is 0, and Z is OH, X—Y is other than meta-C≡—C—(CH2)2CO2H, meta-C≡—C—(CH2)2OH, meta-C≡C—(CH2)2CO2Me, meta-(CH2)4CO2H, ortho-CH2CO2H, ortho-(CH2)2CO2H and ortho-(CH2)4CO2H; and (ii) when A is phenyl, n is 0, and Z is OMe, X—Y is other than meta-C≡C—(CH2)4OH. Further aspects of the invention relate to the use of such compounds in the preparation of a medicament for the treatment of a muscular disorder, a gastrointestinal disorder, or for controlling spasticity or tremors.