RESUMO
Objective: To prepare hydroxytyrosol (HT) by alkaline hydrolysis of oleuropein and to investigate its anti-oxidative property. Methods: According to single factor experiments, four variables: temperature, sodium hydroxide concentration, time, and the ratio of solid to liquid, were selected. On the basis of single factor experiments, orthogonal tests of L9(34) were carried out. HPLC-MS method was also further applied for the qualitative analysis on HT. Under the same conditions, contrast experiments on the acid and alkaline actions were made. Finally, anti-oxidative activity of HT was evaluated. Results: The results showed that the selected variables were all highly significant. Also, the descending influence orders on HT were temperature > sodium hydroxide concentration > time > the ratio of solid to liquid. Lastly, the optimal conditions on HT yield were obtained as follow: temperature 90°C, sodium hydroxide concentration 0.2 mol/L, time 45 min, and the ratio of solid to liquid 1:15. The HPLC retention time of HT was about 10.3 min, and its relative molecular weight of fragment ion by MS was 134.8. By comparison with the acid action, it was proved that the alkaline action was better in HT yield. In addition, the anti-oxidative activity of HT was carried out on scavenging DPPH radical. The results showed that DPPH scavenging capability of HT was 2.45 times of BHT. Conclusion: HT yield is well obtained under the alkaline condition and has a good anti-oxidation.