Complex sentence: Raw cranberries, cranberry and cranberry extracts are a source of polyphenols-including proanthocyanidins and flavonols and quercetin, which are being studied in vivo and in vitro.
Split into simpler sentences: Raw cranberries, cranberry juice and cranberry extracts are a source of polyphenols-including proanthocyanidins, flavonols and quercetin. These compounds are being studied in vivo and in vitro.