Neamphamide B, new cyclic depsipeptide, as an anti-dormant mycobacterial substance from a Japanese marine sponge of Neamphius sp

A new cyclic depsipeptide, designated neamphamide B (1), was isolated from a marine sponge of Neamphius sp. collected at Okinawa, Japan in 1993 as an anti-mycobacterial substance against active and dormant bacilli. The planar structure of neamphamide B (1) was determined on the basis of spectroscopic analysis, and stereostructure of amino acid was deduced by chromatographic comparison of the acid hydrolysate of 1 with appropriate amino acid standards after derivatizing with FDAA or GITC. Neamphamide B (1) showed potent anti-mycobacterial activity against Mycobacterium smegmatis under standard aerobic growth conditions as well as dormancy-inducing hypoxic conditions with MIC of 1.56 μg/mL. Neamphamide B (1) was also effective to Mycobacterium bovis BCG with MIC in the ranging of 6.25-12.5 μg/mL.