Hymenistatin is a

cyclic peptide Cyclic peptides are polypeptide chains which contain a circular sequence of bonds. This can be through a connection between the amino and carboxyl ends of the peptide, for example in cyclosporin; a connection between the amino end and a side chai ...

isolated from the

sea sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through th ...

'' Phakellia fusca''. It is a cyclic octapeptide whose sequence is cyclo le-Ile-Pro-Pro-Tyr-Val-Pro-Leu

References

Cyclic peptides {{organic-compound-stub