The reaction rate started to decrease after a few minutes, and
the de novo synthesis leveled off in the course of 60 min monitored.
Even for the lamella part of the fruiting body, the reaction rate
slowed down after 30 min. As UV-B light is not able to penetrate
deeply into the mycelium, the reaction rate must cease when the
superficial ergosterol is used up. The yields of ergocalciferol are
thus limited, but at the same time the risk of accumulating
extreme doses is low. With molar conversion rates of around
2–3%, the precursor ergosterol, a proven antioxidant (Schneider
et al., 2011), remained almost unchanged. Thus, neither the