Sure you can get a lot even from net vinblastine, vincristine, taxol are anticancer drugs. in the same way other alkaloids Venalstonine, Vindolinine, Flavonoids like (Flavone, Flavanone) Curcumin, Sylmarine, Oleuropien and saponin like Aescine, and frostanol based steroidal saponins from T.tribulus etc are mostly clinically tested .
All clinical trials should be registered in one of the databases that are available online, including those using natural health products/natural compounds.
The ones I know are https://www.clinicaltrialsregister.eu/ for Europe and www.clinicaltrials.gov mostly for North America.
In addition, there should be information on the regulatory websites for each country, e.g. Health Canada for Canada, FDA for the US etc.