Stylissatin A, a cyclic peptide that inhibits nitric oxide production from the marine sponge Stylissa massa

A new cyclic heptapeptide, stylissatin A (1), was isolated from the Papua New Guinean marine sponge Stylissa massa. Through the use of 1D and 2D NMR spectroscopic analysis, Marfey’s method, and MS/MS analysis, its structure was determined to be cyclo-[Tyr1–Ile2–Phe3–Pro4–Ile5–Pro6–Phe7]. Stylissatin A inhibited nitric oxide production in LPS-stimulated murine macrophage RAW264.7 cells with an IC50 value of 87 μM.