Cyclotides (cyclo peptides) are plant peptides of ~30 amino acids with a head to-tail cyclic backbone and six cysteine residues involved in three disulphide bonds. The cyclotides are extremely resistant to proteolysis and are remarkably stable. Cyclotides display a diverse range of biological activities, including uterotonic activity, inhibition of neurotensin binding, hemolytic, anti-HIV and anti-microbial activity. This range of biological activities makes cyclotides amenable to potential pharmaceutical and agricultural applications. Although their precise role in plants has not yet been reported, it appears that they are most likely present as defence molecules [PMID: 10600388, PMID: 12482862, PMID: 12482868, PMID: 12946412].