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The most researched class of compounds isolated from H. perforatum is the naphthodianthrones, which occur in concentrations ranging from 0.1 up to 0.3 (9,25,26). The most common naphthodianthrones include hypericin, pseudohypericin, isohypericin, and protohypericin (10,21). Of those, hyper-icin is the best known and, to date, the most studied.