Kwanzoquinones A–G and other constituents of Hemerocallis fulva ‘Kwanzo’ roots and their activity against the human pathogenic trematode Schistosoma mansoni

Schistosomiasis is a debilitating disease caused by parasitic trematodes of the genus Schistosoma that afflicts 200 million people worldwide. Daylilies (Hemerocallis spp.) have been used in Asia for the treatment of schistosomiasis; however, the active principles have not been fully characterized. In our studies of Hemerocallis fulva ‘Kwanzo’ Kaempfer roots, we have isolated seven new anthraquinones, kwanzoquinones A (), B (), C (), D (), E (), F (), and G (), two known anthraquinones, 2-hydroxychrysophanol () and rhein (), one new naphthalene glycoside, 5-hydroxydianellin (), one known naphthalene glycoside, dianellin (), one known flavone, 6-methylluteolin (), and α-tocopherol. The structures of the compounds were elucidated by spectroscopic and chemical methods. Compounds and the monoacetates of kwanzoquinones A and B, and , respectively, were tested for their activity against multiple life-stages of Schistosoma mansoni. Compound immobilized all cercariae within 15 s at 3.1 μg/mL. However, upon removal of the compound, 20% of the immobilized cercariae recovered after 24 h. In contrast, compound immobilized cercariae within 12–14 min at 25 μg/mL. Following removal of the compound, all cercariae died within 24 h. The adult worms were also immobilized within 16 h by compounds and at 50 μg/mL. None of the compounds had an effect on the schistosomula stage.