The head-to-tail cyclic peptide SunFlower Trypsin Inhibitor-1 (SFTI-1) is produced in the seeds of the common sunflower (Helianthus annuus). It comprises 14 amino acids including two cysteines forming a disulfide bond that together with the cyclic backbone creates a highly stable bicyclic structure. The genetic origin and biosynthesis of SFTI-1 is intriguing. The gene Paws1 encodes a precursor protein with a dual fate, SFT1-1 and an unrelated albumin seed storage protein. The PawS1 precursor is post-translationally processed by an aspariginyl endopeptidase into a mature two-chain albumin, and during this process SFTI-1 is also cleaved out and cyclized. We have used recombinant expression of Paws1 in E. coli to produce isotopically enriched material for NMR studies. The 3D structure of Paws1 was solved using multi dimensional and triple resonance NMR, revealing two independent domains separated by a flexible linker. The SFTI-1 part of Paws1 has an active site loop that is identical to the mature form, while the cyclisation loop lacks definition in this precursor form. Using genetic approaches to search for Paws1 analogues and liquid chromatography-mass spectrometry based screening for SFTI-1 like peptides a number of cyclic and acyclic analogues with structural and sequence homology to SFTI-1 were shown to exist in various species of the family Asteraceae, and we now refer to these as PawS-Derived Peptides (PDPs). NMR spectroscopy was employed to characterize the 3D structures of a number of PDPs showing that in general they form well-defined, rigid structures with a diverse range of folds as a result of their different sequences. The closest relatives of SFTI-1 are able to inhibit trypsin, however, no biological significance for the more structurally diverse peptides remain an enigma.