Difference in protective effects of three structurally similar flavonoid glycosides from Hypericum ascyron against H₂O₂-induced injury in H9c2 cardiomyoblasts.

According to previous studies, hyperoside possesses myocardial protective effects. To investigate whether isoquercitrin and isohyperoside have similar functions, the protective effects of isoquercitrin and isohyperoside against H2O2‑induced injury in H9c2 rat cardiomyoblasts were evaluated using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide assay. The mechanism of action was investigated by assessing the leakage of lactate dehydrogenase (LDH) of hyperoside and isoquercitrin‑pretreated H9c2 cardiomyocytes following H2O2‑induced injury, and examining their effects on the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) activity. The isolation of two flavonoid glycosides from H. ascyron was performed, following extraction, using semi‑preparative high performance liquid chromatography. Using the spectral characteristics, the structures of these compounds were identified as isoquercitrin and isohyperoside. This was the first time, to the best of our knowledge, that isohyperoside has been identified from H. ascyron. The results revealed that isoquercitrin and isohyperoside possessed similar protective effects to hyperoside against H2O2‑induced injury in H9c2 cells. The half maximal inhibitory concentration values of hyperoside, isoquercitrin and isohyperoside were 0.0008, 0.0017 and 0.0002 µM, respectively. Based on these results, isohyperoside possessed more marked protective effects against H2O2‑induced injury in the H9c2 cardiomyoblasts. The significant reduction in LDH leakage, decrease in MDA level and increase in SOD activity also provided evidence of the cardioprotective effects of isoquercitrin and isohyperoside. The present study reported for the first time, to the best of our knowledge, the myocardial protective effects of isoquercitrin and isohyperoside. The mechanism of action may involve protection of the cell membrane from oxidative damage.