Plants and their oils, roots, seeds, berries, or flowers are used to make herbal supplements. Echinacea, flaxseed, ginseng, ginkgo, saw palmetto, St John's wort, black cohosh, evening primrose, milk thistle, and garlic are just a few of the herbal supplements available on the market. Green tea and Ginkgo biloba, for example, have been shown to interact with prescription medicines, according to new study published in the British Journal of Clinical Pharmacology. Herbal supplements have been used to treat a range of illnesses for hundreds of years. Plants and/or their oils, roots, seeds, berries, or berries, as well as their fruits and leaves, are used to make herbal supplements.