Natural Products occupy an important part of small molecule space because they are recognized by at least two proteins: the end of their biosynthetic pathway and their evolutionary biological target. Most of these compounds are for sale, but some are collabocules. Over a third of all drugs are natural products or similar to one. Natural products may be expensive. Please also see the Special Subsets many of which feature natural products and metabolites.
 These databases have been provided to us under collaborative agreements with each respective catalog owner. Catalogs have been filtered for drug discovery relevance, and thus compounds in the original catalog may not be in ZINC. Some documentation on ZINC subsets is available.
ZINC may be used free of charge for research by individuals and institutions. Whereas you are free to share the results of a ZINC search or a screen of molecules from ZINC, you may not redistribute major portions of ZINC without the express written permission of John Irwin.