Most natural products are not adequately regulated in most countries and some are not regulated as medical products at all. I do not think there is any database with adverse events related to natural products as their is no clear reporting framework or reporting obligations for these products.
You can try this website: http://bioinformatics.charite.de/transformer/index.php?site=drug_search
I do not know what natural products are in this database, but you can try it out. It will give you the drug-drug and drug-gene interactions within the CYP450 system.