Chemo-enzymatic synthesis of sapienic acid esters of functional phenolics and evaluation of their antioxidant and cytotoxicity activities

Novel fatty acid ester derivatives comprising sapienic acid [(Z)-6-hexadecenoic acid] and functional phenolics were synthesized following a chemo-enzymatic approach. Sapienic acid was synthesized by Wittig coupling of triphenylphosphonium bromide salt of 6-bromohexanoic acid and decanal with a cis specific reagent. Sapienic acid was chemo selectively esterified with six phenolic compounds to produce sapienate esters of six phenolics using a lipase in organic solvent medium. Structural characterization of the prepared fatty acid ester derivatives was done by spectral data (IR, mass spectra, and NMR). The sapienic acid ester derivatives were screened for in vitro antioxidant and cytotoxicity evaluation. These derivatives exhibited good radical scavenging activity as determined by the diphenylpicryl hydrazyl (DPPH) radical scavenging assay. Sapienic ester of hydroxytyrosol was found to exhibit highest DPPH radical scavenging activity and was greater than commercial antioxidants. Cytotoxicity evaluation against four cancer cell lines showed that three esters out of six were found to exhibit moderate cytotoxicity with coniferyl derivative being more active than the others against all the tested cell lines.