Hydrolases-mediated transformation of oleuropein into demethyloleuropein
Phenolic compounds present in extra virgin olive oil have recently attracted considerable attention due to their pharmacological activities. Among them oleacein (3,4-DHPEA-EDA), structurally related to oleochantal (4-HPEA-EDA), is one of the most studied. 3,4-DHPEA-EDA has been synthesized through decarboxylation of demethyloleuropein catalyzed by Er(OTf)3. Demethyloleuropein is extracted from black olives drupes in very limited amounts and only in particular periods of the year. The availability of demethyloleuropein could be increased by a selective hydrolysis of the methyl ester moiety of oleuropein, a secoiridoid present in large amount in olive leaves. In this work we describe a new enzymatic method for carrying out a selective hydrolysis of oleuropein via the screening of a panel of hydrolases (lipases, esterases and proteases). Among all the enzymes tested the best results was obtained using α-chymotrypsyn from bovine pancreas as biocatalyst, thus revealing a classic example of catalytic enzyme promiscuity.