Antioxidant activity of oak (Quercus) leaves infusions against free radicals and their cardioprotective potential

The aim of present study was to evaluate antioxidant capacity and cardioprotective potential of leaves infusions and partially purified fractions of Quercus sideroxyla and Q. eduardii (red oaks) and Q. resinosa (white oak). Consumption of polyphenol-rich beverages derived from plants, such as oak may represent a beneficial diet in terms of cardiovascular protection. Infusions from Oak leaves were obtained and probed for total phenolics by Folin-Ciocalteu, DPPH and hydroxyl radicals scavenging by DPPH test and Deoxy-D-ribose method, the antioxidant capacity was evaluated by FRAP and ORAC tests, inhibitions of Low Density Lipoproteins (LDL) oxidation and Angiotensin Converting Enzyme (ACE) activity were measured. A HPLC analysis was performed by HPLC-MS. Bioactive polyphenols such as gallic and ellagic acids, catechin, quercetin and derivatives: naringenin and naringin were detected in Quercus infusions. A distinctive HPLC profile was observed among the red and white oak samples. Q. resinosa infusions have exhibited the highest antioxidant activity in comparison with the other species, although in the inhibition of LDL oxidation no differences were observed. In the inhibition of the ACE, Q. resinosa was more effective (IC50, 18 ppm) than Q. sideroxyla, showing same effect as the control Captopril. From the results it is possible to postulate that not only chelating activity is important in these infusions, especially in Q. resinosa.