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Furthermore , we observed that the oppositely directed H ( + ) - gradient can drive the secretion of metformin from placenta to maternal circulation , confirming apical efflux of metformin from trophoblast by MATE1 .
 Chemical: H ( + ); Chemical: metformin; Chemical: metformin
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: metformin; Chemical: metformin