Effects of Olive Metabolites on DNA Cleavage Mediated by Human Type II Topoisomerases.
Biochemistry. 2015 Jul 1. Epub 2015 Jul 1. PMID: 26132160
Kendra R Vann
Several naturally occurring dietary polyphenols with chemopreventive or anticancer properties are topoisomerase II poisons. In order to identify additional phytochemicals that enhance topoisomerase II-mediated DNA cleavage, a library of 341 Mediterranean plant extracts was screened for activity against human topoisomerase IIα. An extract from Phillyrea latifolia L., a member of the olive tree family, displayed high activity against the human enzyme. Based on previous metabolomics studies, we identified several polyphenols (hydroxytyrosol, oleuropein, verbascoside, tyrosol, and caffeic acid) as potential candidates fortopoisomerase II poisons. Of these, hydroxytyrosol, oleuropein, and verbascoside enhanced topoisomerase II-mediated DNA cleavage. The potency of these olive metabolites increased 10- to 100-fold in the presence of an oxidant. Hydroxytyrosol, oleuropein, and verbascoside displayed hallmark characteristics of covalent topoisomerase II poisons: 1) the activity of the metabolites was abrogated by a reducing agent, 2) compounds inhibited topoisomerase II activity when incubated with the enzyme prior to the addition of DNA, and 3) compounds were unable to poison a topoisomerase IIα construct thatlacked the N-terminal domain. Because hydroxytyrosol, oleuropein, and verbascoside are broadly distributed across the olive family, extracts from the leaves, bark, and fruit of 11 olive tree species were tested for activity against human topoisomerase IIα. Several of the extracts enhanced enzyme-mediated DNA cleavage. Finally, a commercial olive leaf supplement and extra virgin olive oils pressed from a variety of Olea europea subspecies enhanced DNA cleavage mediated by topoisomerase IIα. Thus, olive metabolites appear to act as topoisomerase II poisons in complex formulations intended forhuman dietary consumption.