A compound (including salts thereof) according to Formula I in which R1 is H, methyl or ethyl R2 is H, OH, fluorine, C1-C4 linear or branched alkyl, C1-C6 alkoxy wherein the alkyl group is linear or branched, or a C3-C5 cycloalkyl moiety R3 is H, methoxy, methyl or ethyl or R2 and R3 together form a bridging moiety -O-CH2-O- between the phenyl carbon atoms to which they are connected R4 is OH or methoxy and R5 and R6 are independently H or methyl R1, R2, R3, R4, R5 and R6 are such that, (i) when R2 and R3 together form a bridging moiety -O-CH2-O- between the phenyl carbon atoms to which they are connected, R1, R5, R6 are H, and R4 is OH and (ii) when R4 is OH and R1-R3 are H, at least one of R5, R6 is methyl.
