Anticancer activity of flavonoids isolated from spent hops and their derivatives obtained by microbial transformations

Hops are primarily used in beer brewing to add bitterness and flavour to beer. It is also good source of desired, biologically active prenylated flavonoids. The major prenylflavonoids from hops is xanthohumol, which it is known from its various biological properties such as antioxidant [1], anti-inflammatory [2], antibacterial [3], antiviral [3], antifungal [4] and antiplasmodial [5] activities.  Xanthohumol was isolated from spent hops - the CO2 extracted hops, a waste product of the hop processing industry. Xanthohumol was extensively tested as a substrate for microbial transformations using over one hundred and forty strains including bacteria, yeasts and fungi. It was also used for the synthesis of other naturally occuring hop prenylfalvonoids such as isoxanthohumol, 8-prenylnaringenin and their synthetic derivatives. Obtained microbial and synthetic compounds were examinated for antiproliferative activity against human cancer cell lines. Tested flavonoids, among them the natural ones,  showed potent anticancer activity, while several of them were more active than cisplatin, the reference drug used in anticancer therapy. Our studies showed how the antiproliferative activity depends on the molecular structure of prenylated flavonoinds (SAR) and indicates that xanthohumol derivatives can be recognized as potential drugs used in anticancer treatment.