According to the Natural Products Branch, which is a part of the Developmental Therapeutic Program of NCI (National Cancer Institute), agencies worldwide are collecting thousands of samples of plants and other natural product sources (such as marine organisms) to research and identify new molecules. It is estimated that only 1% of the approximately 500,000 plant species worldwide have been thus far investigated for their medicinal properties. (Palombo, 2006).
Hartwell (1969, 1970, 1971) surveyed and collected data on about 3000 plants known to possess anticancer properties. Half of all the anticancer drugs approved globally are either based on or derived from natural products. New drugs are also being continuously discovered and entering the market.
Ayurveda and Traditional Chinese Medicine, two of the largest and the most popular herbal systems of the world, together make a mention of under 1500 plants with medicinal properties.
Most modern medicine available to us today is of plant origin. It is only later in the drug discovery lifecycle that drugs move to chemical-based manufacture. Chemical-based manufacturing helps bring consistency in efficacy and ease of manufacture than plant-based drugs where there are challenges for raw materials, genetic inconsistency, and fear of mutations.
The world of plants is huge, and there is still a lot to explore. To take a deep dive into the world of plants and natural solutions you can explore this selection of books.