18933
SAR analysis indicates that H - donor substitution at C - 3 position of oleanolic acid may be advantageous for improvement of cytotoxicity against PC3 , A549 and MCF - 7 cell lines .
 Chemical: H; Chemical: oleanolic acid
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: H; Chemical: oleanolic acid