An antimicrobial agent

A compound of general formula (I): wherein R1 and R2 may be the same or different and are selected from the group consisting of hydrogen, optionally substituted C4-30 alkyl and optionally substituted C4-30 alkenyl, provided that R1 and R2 may not both be hydrogen, or R1 and R2 together with the nitrogen atom from which they depend form a saturated or unsaturated, optionally substituted heterocyclic group which may include additional heteroatoms selected from the group consisting of O, N and S, or R1 and R2 together with the nitrogen atom from which they depend form an optionally substituted lactam moiety; X1 is selected from the group consisting of OR3, SR3, NR3R'3, hydrogen, halogen, CN, C(O)NR3R'3, C(O)OR3, OSO3R3, OPO3R3, NNR3R'3, SNR3R'3, NHSR3, SSR3 and substituted alkyl; X2 is selected from the group consisting of OR4, SR4, NR4R'4, hydrogen, halogen, CN, C(O)NR4R'4, C(O)OR4, OSO3R4, OPO3R4, NNR4R'4, SNR4R'4, NHSR4, SSR4 and substituted alkyl; X3 is selected from the group consisting of OR5, SR5, NR5R'5, hydrogen, halogen, CN, C(O)NR5R'5, C(O)OR5, OSO3R5, OPO3R5R'5, NNR5R'5, SNR5R'5, NHSR5, SSR5 and substituted alkyl; X4 is selected from the group consisting of OR6, SR6, NR6R'6, hydrogen, halogen, CN, C(O)NR6R'6, C(O)OR6, OSO3R6, OPO3R6R'6, NNR6R'6, SNR6R'6, NHSR6, SSR6 and substituted alkyl; R3, R'3, R4, R'4, R5, R'5, R6 and R'6 are the same or different and are selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted aralkyl, optionally substituted aryl, optionally substituted acyl and a carbohydrate moiety; or a pharmaceutically acceptable salt thereof.