Valoneic acid dilactone is a hydrolysable tannin that can be isolated from the heartwood of Shorea laevifolia and in oaks species like the North American white oak (Quercus alba) and European red oak (Quercus robur). It shows an inhibitory effect on 5α-reductase, an enzyme involved in steroids metabolism and prostate cancer. References External links Ellagitannins 5α-Reductase inhibitors Lactones Trihydroxybenzoic acids