Techniques for topic extraction and opinion mining are described. For example, a machine accesses a document from a document record of a database. The machine builds a syntax tree of a sentence of the document based on parsing the sentence. The machine assigns a polarity impact to one or more words of the sentence. The machine determines that a plurality of words in the sentence have conflicting polarity based on the syntax tree and the polarity impact of the plurality of words. The machine determines a classification of the sentence based on the determining that the plurality of words in the sentence have conflicting polarity. The machine generates a classification record of the classification in the database.