Novel uses of porphyrin compounds

A method for killing or attenuating the growth of microorganisms comprising administering to a patient an effective amount of a compound of Formula I or II

• wherein:
• X1, X2, X3 and X4 independently represent a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group, or a cationic group of the following formula;
• —L—R1—N+(R2)(R3)R4
• wherein:
• L is a linking moiety or is absent;
• R1 represents lower alkylene, lower alkenylene or lower alkynylene, which is optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), fluoro, OR5, C(O)R6, C(O)OR7, C(O)NR8R9, NR10OR11 and N+R12R13R14;
• and
• R2, R3 and R4 independently represent H, aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR5, C(O)R6, C(O)OR7, C(O)NR8R9, NR10R11 and N+R12R13R14
• Z is —CH or N;
• and
• Y1, Y2, Y3 and Y4 are absent or independently represent aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR5, C(O)R6, C(O)OR7, C(O)NR8R9, NR10R11, N+R12R13R14, or, taken in conjunction to the pyrrole ring to which they attach, forms a cyclic group;
• and
• R5, R6, R7, R8, R9, R10, R11, R12, R13 and R14 independently represent H or lower alkyl
• provided that at least one of X1, X2, X3 and X4 is a cationic group as defined above and at least one of X1, X2, X3 and X4 is a hydrogen atom,
• M is a metallic element or a metalloid element, and
• wherein the compound of Formula I or II is not exposed to a stimulus which activates antimicrobial activity.