25773
It was found that the PAMPA - BBB assay preserves its predictive power in the case of natural products and provides high phytochemical selectivity , which enables its use as a unique filtering tool in terms of selecting brain - penetrable compounds from plant extracts .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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