During the last decade, the drug industry has followed an assumption that a single drug hitting a single target was the "rational" way to design drugs. We're learning that Mother Nature may be a bit too complicated for that. "Strategies for targeting single genes or proteins ignore a very important fact that most, if not all diseases, involve a sophisticated network system." For example, one little family of immune molecules involves about 50 different keys fitting into about 20 different locks, often acting with redundancy, making selection of an appropriate drug to antagonize one key or one lock ineffective in the long run. A whole list of agents has been developed to target a specific molecule for the treatment of inflammatory bowel disease, for example, but they have all flopped. That's why drug companies are now working on so-called "promiscuous" drugs that try to affect multiple pathways simultaneously.
Meanwhile, since ancient times, natural agents derived from plants-fruits, vegetables, spices, beans, and grains-have been preferred as potential therapeutics for most chronic diseases, not only because of their safety, affordability, and long-term use, but also "for their ability to target multiple cell signaling pathways, a therapeutic virtue."