In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

Q: RDH12, a retinol dehydrogenase causing Leber's congenital amaurosis, is also involved in steroid metabolism.

A: retinol
****
Q: Manipulation of kinetic profiles in 2-aryl propionic acid cyclooxygenase inhibitors.

A: 2-aryl propionic acid
****
Q: The dynamics of cobalamin utilization in L-1210 mouse leukemia cells: a model of cellular cobalamin metabolism.

A:
cobalamin
****