Chrysin, also called 5,7-dihydroxyflavone, is a flavone found in honey, propolis, the passion flowers, Passiflora caerulea and Passiflora incarnata, and in Oroxylum indicum. It is extracted from various plants, such as the blue passion flower (Passiflora caerulea). Following oral intake by humans, chrysin has low bioavailability and rapid excretion. It is under basic research to evaluate its safety and potential biological effects. Chrysin is an ingredient in dietary supplements. As of 2016, there was no clinical use of chrysin, and no evidence for its effect on testosterone levels. In 2016, the US Food and Drug Administration did not recommend chrysin be included on the list of bulk drug substances that can be used in compounding under section 503A of the Federal Food, Drug, and Cosmetic Act. Occurrence A component in various medicinal plants (e.g. Scutellaria baicalensis), chrysin is a dihydroxyflavone, a type of flavonoid. It is also found in honey, propolis, the passion flowers, Passiflora caerulea and Passiflora incarnata, in Oroxylum indicum, carrots, chamomile, many fruits, and in mushrooms, such as the mushroom Pleurotus ostreatus. It is extracted from various plants, such as the blue passion flower (Passiflora caerulea). The amount of chrysin in honey from various plant sources is about 0.2 mg per 100 g. Chrysin is typically found at higher amounts in propolis than in honey. A 2010 study found the amount of chrysin was 0.10 mg/kg in honeydew honey, and 5.3 mg/kg in forest honeys. A 2010 study found the amount of chrysin in propolis was as much as 28 g/L. A 2013 study found the amount of chrysin in various mushrooms from the island of Lesvos, Greece, varied between 0.17 mg/kg in Lactarius deliciosus to 0.34 mg/kg in Suillus bellinii. Bioavailability The effects of chrysin are reliant on its bioavailability and solubility. Following oral intake by humans, chrysin has low bioavailability and rapid excretion. As a result, it is poorly absorbed. A 1998 study determined that the highest amounts in plasma was from 12 to 64 nM. As of 2015, the serum levels of chrysin have not been cited in the literature. Following oral intake by humans, the bioavailability was reported to be from 0.003% to 0.02%. Oral and topical application There is insufficient information to determine how long chrysin has been used in pharmacy compounding. Chrysin is used as an ingredient in dietary supplements, but there is no information on systemic exposure from topical application.