Research Article Antioxidant activity of phosphatidyl derivatives of hydroxytyrosol in edible oils Diana Martin 1,2 , Alba Garcia‐Serrano 1,2 , Víctor Casado 1,2 , Luis Vázquez 1,2 , Guillermo Reglero 1,2,3 and Carlos F. Torres 1,2 1 Departamento de Producción y Caracterización de Nuevos Alimentos, Instituto de Investigación en Ciencias de la Alimentación (CIAL), CEI UAMþCSIC, Madrid, Spain 2 Facultad de Ciencias, Sección Departamental de Ciencias de la Alimentación, Universidad Autónoma de Madrid, CEI UAMþCSIC, Madrid, Spain 3 Imdea‐Food Institute, CEI UAMþCSIC, Madrid, Spain A comparative study of the antioxidant activity of hydroxytyrosol (HT) and phosphatidyl derivatives of hydroxytyrosol (PHT) added at increasing concentrations to diverse edible oils (lard oil, refined olive oil, and diacylglycerol‐rich oil) was performed. Antioxidant activity index was estimated as the ratio of induction time in presence of the compounds to induction time in their absence, after oxidation under Rancimat conditions. Tocopherol (TOC) and phosphatydilcholine (PC) were used as reference, and combinations PHT:TOC, PHT:PC, HT:TOC, and PC:TOC were also tested. PHT and HT showed a protective effect as the added concentration of antioxidants increased. However, the protective effect of PHT was superior to HT for olive oil and diacylglycerol oil, and similar to HT for lard oil. The magnitude of the protection of both PHT and HT was higher in lard oil, followed by olive oil and the poorest protection was for diacylglycerol oil. Both HT and PHT were superior to TOC. Furthermore, PC showed a lack of antioxidant activity compared to PHT. A lack of synergism between the combinations of antioxidants was found. Practical applications: Including phosphatidyl derivatives of hydroxytyrosol in edible oils provides two advantages. First, they serve as a source of hydroxytyrosol and second they stabilize the lipid matrix, and in this respect the phosphatidyl derivatives perform better than hydroxytyrosol or tocopherols. Keywords: Antioxidants / Edible oils / Hydroxytyrosol / Lipid delivery / Phospholipids Received: January 27, 2014 / Revised: March 21, 2014 / Accepted: April 8, 2014 DOI: 10.1002/ejlt.201400053 1 Introduction The popularity of phenolic compounds in general as bioactive natural antioxidants is currently well known [1–3]. Within polyphenolic compounds, hydroxytyrosol (HT) is being an attractive molecule in the last decades that have shown a great bioactivity and antioxidant power, related to antiatherogenic, antiplatelet aggregation, anti‐inflammatory, antimicrobial, and antitumor effects, or regulation of aging [4–6]. HT has been described as an antioxidant with a high hydrophilic/lipophilic balance (HLB), and solubility in polar media is preferred. This circumstance determines the mode of interaction with membrane cells, its metabolism, bioavailability, or antioxidant effect, which finally determines the magnitude of its final effect. On the other hand, its bioavailability is poor because it is rapidly metabolized in enterocyte and liver to minor metabolites and free intact HT is only found at minor levels in plasma and tissues [7, 8]. Furthermore, it has been also shown that absorption and excretion of HT and metabolites varies depending on the vehicle used in the administration of the compound [9]. Correspondence: Dr. Diana Martin, Departamento de Producción y Caracterización de Nuevos Alimentos, Instituto de Investigación en Ciencias de la Alimentación (CIAL), Campus de la Universidad Autónoma de Madrid, 28049 Madrid, Spain E‐mail: diana.martin@uam.es Fax: þ34 910017905 Abbreviations: AAI, antioxidant activity index; DO, DAG‐rich oil; ELSD, evaporative light scattering detector; HLB, hydrophilic/lipophilic balance; HT, hydroxytyrosol; LO, lard oil; PC, phosphatidylcholine; PHT, phospha- tidylhydroxytyrosol; OO, refined olive oil; TOC, tocopherol; TPC, total phenolic compounds Eur. J. Lipid Sci. Technol. 2014, 116, 1035–1043 1035 ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com