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

[EX Q]: Neuroprotective and anti-inflammatory properties of a coffee component in the MPTP model of Parkinson's disease.
[EX A]: MPTP

[EX Q]: Oncolytic activity and mechanism of action of a novel L-cysteine derivative, L-cysteine, ethyl ester, S-(N-methylcarbamate) monohydrochloride.
[EX A]:
L-cysteine