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.

[EX Q]: Analysis of mammalian alcohol dehydrogenase 5 (ADH5): characterisation of rat ADH5 with comparisons to the corresponding human variant.
[EX A]: alcohol

[EX Q]: Nuclear receptors in bile acid metabolism.
[EX A]: bile acid

[EX Q]: The effects of the phosphodiesterase type 5 inhibitor vardenafil on cognitive performance in healthy adults: a behavioral- electroencephalography study.
[EX A]:
vardenafil