Hydrocyanic acid is a poison property of ginkgo biloba. Hydrocyanic acid suppress the respiratory enzyme, induce cell hypoxia and suffocation. That will cause headache, fatigue, hard breathing, acute blood pressure increasing, coma, respiratory failure, even cardiac arrest and death. Another poison property of ginkgo biloba is ginkgo acid. Ginkgo acid is one of the most intense exposure allergens, would lead to severe allergic reaction. Additionally, it also would damage the gastrointestinal and myocardial cells, caused gastrointestinal mucosa allergens and shock.
The above two properties are the main known poison components, so the ginkgo biloba on the market has standard on the concentration of this two composition. The ginkgo acid should below 1 parts permillion(ppm) in the recent Europe ginkgo biloba standard. Unfortunately, the standard about hydrocyanic acid was not provided in this standard. But the hydrocyanic acid concentration is very very low in ginkgo biloba, it would not effect human health normally.
Through it has standard of ginkgo biloba to avoid the poison properties harm human, we should take care when we use ginkgo biloba. The dosage should not be high, especially when you take ginkgo biloba the first time. Because the hydrocyanic acid and ginkgo acid is very abundant in leaf, the ginkgo leaf, which was not treated or extracted, should not be taken.