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.

Example Input: Ellagic acid attenuates bleomycin and cyclophosphamide-induced pulmonary toxicity in Wistar rats.
Example Output: bleomycin

Example Input: The role of extranuclear signaling actions of progesterone receptor in mediating progesterone regulation of gene expression and the cell cycle.
Example Output: progesterone

Example Input: Efficient induction of apoptosis in HeLa cells by a novel cationic porphycene photosensitizer.
Example Output:
porphycene