"Non-Taxifolin" Derived Flavonolignans: Phytochemistry and Biology

Flavonolignans are plant natural products, composed of a flavonoid moiety and a lignan (phenylpropanoid) part. Current literature focuses on flavonolignans formed from taxifolin and coniferyl alcohol as e.g. silybin and its congeners from fruit extract from the purple variety of the milk thistle (Silybum marianum) denoted as "silymarin". This review describes chemistry and biological activity of so far neglected "non-taxifolin" based flavonolignans, derived from apigenin, luteolin, tricin, chrysoeriol, naringenin and eriodictyol, as the flavonoid part. Up-to-date knowledge on hydnocarpin, hydnocarpin-D, pseudotsuganol, hydnowightin, neohydnocarpin, palstatin, salcolins A and B, anastatins A and B, sinaiticin, silyamandin and silandrin is summarized in the present paper. Most of non-taxifolin derived flavonolignans have been shown to exhibit in vitro and/or in vivo anti-hepatotoxic, anti-oxidant, free radical scavenging, anti-inflammatory, anti-proliferative, anti-cancer, chemotherapy potentiating, anti-melanogenic, anti-bacterial, vasorelaxing, anti-platelet aggregation and/or hypotriglyceridemic activity, often stronger than silybin. Many of these compounds inhibited Staphylococcus aureus multidrug resistance pump NorA and sensitized multidrug resistant cancer cell lines showing a potential as adjuvants. Non-taxifolin derived flavonolignans are a relatively unexplored group of compounds with interesting biological activity and great application potential. Their detailed study could provide a new insight into the biomimetic synthesis in order to obtain new compounds with greater activity and identify new lead structures for the biomedicinal research.