Anti-tumor Properties of Stilbene-based Resveratrol Analogues: Recent Results

Abstract

Recent literature about stilbene-based analogues of resveratrol (1) has been reviewed, and a total of 94 compounds are reported (see structures 4 – 97), selected either for their promising anti-tumor properties or as comparative terms in SAR studies. As a general outline, these recent literature data confirm the previously reported observation that minimal modification in the nature and position of the substituents on the stilbene nucleus may cause large variations in their biological activity and, more specifically, in their anti-tumor properties. Among the polyhydroxylated stilbenes, it has been established that those with either a catechol or pyrogallol moiety are far better radical scavengers than either 1 or other analogues lacking an ortho-dihydroxy group, and this property was shown to be related to pro-apoptotic activity. In the large majority of cases where couples of E- and Z-isomers were evaluated for either cytotoxic or pro-apoptotic activity, the Z-isomers were significantly more active than their E analogues; nevertheless, a general rule stating that stilbenoids with Z configuration of the double bond display a considerably higher antiproliferative activity than their E-isomers cannot be considered as established. A variety of methoxystilbenes has been reported recently: in many cases these analogues showed either potent antiproliferative and pro-apoptotic activity or strong inhibition of TNFα-induced activation of NF- kB. Globally considered, polymethoxystilbenes are a sub-group of great interest among the resveratrol analogues: these analogues appear worthy of a deeper evaluation also in connection with their potential anti-angiogenic properties. In addition, in vivo studies indicate that methoxystilbenes undergo different metabolic conversion and have a higher bioavailability than resveratrol. The potent activity of some amino- and halogenated stilbenes is undoubtedly worthy of attention, but the toxicity of these compounds to normal cells has rarely been evaluated. In conclusion, the synthesis and evaluation of stilbene-based resveratrol analogues proved to be a highly active field of research and has recently afforded compounds with either cytotoxic or pro-apoptotic activity in the nanomolar range. Nevertheless, the exact structural determinants to optimize the anti-tumor properties of these compounds and details of their mechanism of action remain to be clarified.