Racemomycin-A, -C and -B, like racemomycin-D, exhibited insecticidal activity against the adults of Blattella germanica and Musca domestica. These racemomycin compounds, like racemomycin-D, also showed a delayed toxicity on the adult of Blattella germanica. The insecticidal effect of racemomycin-A, -C and -B on both insects was in the order of B>C>A. As the number of β-lysine residues increased, the antibacterial effect increased along with the insecticidal effect. However, racemomycinic A acid, produced by opening of the lactam ring of the streptolidine moiety of racemomycin-A, showed no insecticidal effect. This would suggest an intimate relationship between the streptolidine moiety in the molecule of streptothricin antibiotics and the activity. Citromycin, a streptothricin-like antibiotic, also exhibited an insecticidal effect against the adults of Blattella germanica and Musca domestica, like racemomycin series compounds.
