There are described compounds of general formula (I) and isomeric forms thereof wherein n is 0, 1, 2 or 3, saturated or unsaturated; most preferably at least one of R1 to R5 represents halogen; at least one of R1, R2, R3, R4 and R5 is selected from —S—R or —COOR, or two or more Of R1-R5 comprise a linking group such as —S—(CH2)mS—, where m is 1, 2 or 3 and R is selected from alkyl having 1 to 5 carbon atoms, cycloalkyl having 3-6 carbon atoms, hydroxy, and aryl having 6 to 10 carbon atoms, such groups being optionally substituted, and when R1 is selected from —S—R, then at least one of R2, R3 and R5 is most preferably selected from halogen; and R1, R2, R3, R4 and R5 are otherwise the same or different and are selected from hydrogen, halogen, alkyl having 1 to 5 carbon atoms, electron donor groups such as alkoxy having 1-5 carbon atoms or hydroxy, electron acceptor groups selected from cyano, nitro, trifluoroalkyl or amide; alkylamino, benzoyloxy, nitroxy, phenyl or sulpho; and pharmacologically acceptable salts thereof. Compounds described have activity on the melanocortin receptors and have application in the treatment of a wide range of inflammatory, arthritic or central nerve regeneration conditions.