Hydroxy Radical Mediated DNA Oxidative Damage Protective Effect of Polyphenols from Lycopus lucidus Turcz. at Different Harvest Times

The phenolic content of free and bound phenolic extracts from Lycopus lucidus Turcz. harvested from two sites (S1 and S2) at three different times (T1, T2 and T3) was determined by Folin-Ciocalteu method. The content of gallic acid, chlorogenic acid, caffeic acid and rosmarinic acid in the phenolic extracts was detected by HPLC. Meanwhile, the protective effect of polyphenolic extracts on ·OH mediated DNA oxidative damage was evaluated. The results revealed that the phenolic contents of free and bound phenolic extracts were in the range of 86.53~181.40 and 89.70~193.58 μg GAE/mg, respectively. Higher amount of caffeic acid was found in the bound phenolic extract and the content of S2 L. lucidus Turcz. was higher than that of S1. Where as higher amount of rosmarinic acid was observed in the free phenolic extract. Furthermore, the rosmarinic acid content in S2 L. lucidus Turcz. was higher than that of S1 at T1 and T3. On the contrary, lower rosmarinic acid content was detected in S2 L. lucidus Turcz. at T2. The contents of caffeic acid and rosmarinic acid varied greatly with the harvest sites. The percentage of DNA double helices of free (25~300 μg/mL) and bound phenolic extracts (3.125~50 μg/mL) were in the range of 1.81%~55.04% and 1.67%~70.83%, respectively. The DNA damage protective effect of bound phenolics was higher than that of free phenolics.