I hear high dose melatonin 75mg has been used safely for years in women in some place in europe and it is said to work as a contraceptive at such high dose(though this is still debated).
Would need more research, as lot of articles saying melatonin might interfere with birth control. Of course cheap unpatentable natural substances always under attack, and barely any research goes into them(hear FDA even threatens on making them drug requiring prescription if research proves too much effectiveness regardless of safety, as melatonin is rumored safer than water.)
Melatonin is a naturally occurring hormone that helps regulate when we feel tired. Learn how it interacts with birth control.
www.sleepfoundation.org
article discussing melatonin's older research as potential contraceptive.
Another article on melatonin
www.ncbi.nlm.nih.gov
It also affects sperm quality at certain doses, so it might even be able to function as male contraceptive with proper dosing.
Another interesting factoid
Why did Slate start a sleep blog? Find out here.
slate.com
Very good book on the importance of melatonin is Walter Pierpaoli's the melatonin miracle
A few case studies suggest very high potential.
A patient with parkinson's at 70s iirc, got cured of parkinsons and lived to 102 a very high age.
Identical twins with a diagnosis of alzheimers, one on melatonin saw no progress of alzheimer's while the other without melatonin suffered massive loss of function.
Melatonin and aging:
culturapierpaoli.ch