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]: High-mannose-type glycan modifications of dihydrofolate reductase using glycan-methotrexate conjugates.
[EX A]: dihydrofolate

[EX Q]: Reinforcement enhancing effects of nicotine via smoking.
[EX A]: nicotine

[EX Q]: Inhibition of testicular LDH-X from laboratory animals and man by gossypol and its isomers.
[EX A]:
gossypol