10.22376/ijpbs.2019.10.1.p1-12 Volume 6 Issue 1 2015 (January - March) Cereulide and valinomycin are both cyclic depsipeptides with 12 stereogenic centers that have a very similar sequence in the structure. Both compounds are hexagonal cylinder-like framework and all the side chains stick outside of the framework. The framework of cyclic D,L-α-peptides were structured different from the cereulide and valinomycin which are performed by cyclic DDLL-peptides. The cyclic D,L-α-peptides consisted of an even number of alternating D- and L- α-amino acid which can adopt flat and stack to form hollow, b-sheet like tubular structures. The amino acid side chains are presented on the outside surface of the framework and the interior surface of such a tube is hydrophilic. In our studies, we found that the original cereulide and valinomycin demonstrated higher antimicrobial activity than the cyclic D,L-α-peptides which are synthesized by using cereulide and valinomycin as a model structure. Furthermore, the combinations of cereulide or valinomycin with clinically used drugs against fungi were found to enhance the antimicrobial efficacy by decreasing the MIC values between 2-128 times. ARTHIT MAKARASEN, NANTHAWAN REUK-NGAM, PIYACHAT CHUYSINUAN, CHAIYAWAT AONSRI, NITIRAT CHIMNOI, MINORU ISOBE AND SUPANNA TECHASAKUL Cereulide, Valinomycin, Cyclic peptide, D,L-α-peptides 77-85