I've done some searching looking for good sites both for checking for drug / herbal interactions (Drugs.com) They allow you to enter all the drugs you currently take and all the supplements you currently take and then show you the interactions to watch out for :
http://www.drugs.com/drug_interactions.php
And for checking on the validity of herbal supplement claims. This website also shows the references for each claim if you are interested in where the data comes from! (Memorial Sloan Kettering Cancer Center) They allow you to do a search of any herbal supplements and then give the claims and the research from which those claims were developed: (you have to scroll to the bottom of the page to find the place to enter your supplement)
https://www.mskcc.org/cancer-care/tr...medicine/herbs