The present disclosure relates to a compound of formula (I), or a pharmaceutically acceptable salt thereof, wherein Z is selected from OH, NHCH2CH2F, NHCH(Me)CH2OH and NHCH2CH2OH; 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 phenyl or pyridyl; and B is (CH2)n where n is 0; with the proviso that: (i) when A is phenyl, and Z is OH, X—Y is other than C≡C—(CH2)2CO2H, C≡C—(CH2)2CO2Me, (CH2)4CO2H. Uses of such compounds as medicaments for the treatment of a muscular disorder, a gastrointestinal disorder, or for controlling spasticity or tremors are provided.