We have been continually searching for novel chemical compounds from culture broths of various actinomycetes using a physicochemical screening system. During the course of this program, we have previously reported the discovery of two new natural products, designated mangromicins A and B, discovered in a broth of a rare actinomycete strain, Lechevalieria aerocolonigenes K10-0216. Mangromicins have a unique and rare structure, a cyclopentadecane skeleton with a tetrahydrofuran unit and a 5,6-dihydro-4-hydroxy-2-pyrone moiety. New mangromicin analogs were isolated by using an improved production medium. As a consequence, six analogs, together with mangromicins A and B, were isolated from a cultured broth of L. aerocolonigenes K10-0216. We named them mangromicins D, E, F, G, H and I. All mangromicins showed radical scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and nitric oxide generated from LPS-stimulated RAW264.7 cells, a murine macrophage cell line. Among the analogs, mangromicins A and I showed the most potent DPPH radical scavenging activity and nitric oxide scavenging activity, respectively.