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 chain, for example in bacitracin ; the carboxyl end and a side chain, for example in colistin ; or two side chains or more complicated arrangements, for example in amanitin . Many cyclic peptides have been discovered in nature and many others have been synthesized in the laboratory. Their length ranges from just two amino acid residues to hundreds. In nature they are frequently antimicrobial or toxic; in medicine they have various applications, for example as antibiotics and immunosuppressive agents. 
I tried the cup of raisins before bed and woke up before dawn with an erection reminiscent of days gone by, that lasted for over an hour. Pretty awesome! Though peeing was a long and drawn out affair.
I just had my T checked as I was not getting them any more, neither was I much interested in sex. The test came back with a paltry 305 @ 46yrs old. Just a year ago my erections used to have a bitter sweet ache to them. After going close to zero carb I lost my power, my head hair, got rosacea, limp erections, and my nitric oxide plummeted. I stopped training as it was painful and although I was eager to exercise my body just didn’t seem up to it. ( come to think of it now after reading all these articles, it would seem that lower elasticity of my arteries(low NO) was the reason.)