Purpose: Discovering new antimyocardial
ischemia drug candidates that are highly efficient, have low toxicity, and originate from natural products is a popular trend for new
cardiovascular drug development at present. The
ethanol extract of Livistona chinensis leaves showed a favorable
antioxidant activity in our preliminary screening test. This study aims to screen out
antioxidants from the herb leaves further and evaluate their efficacy in acute
myocardial ischemia treatment at the cellular level. Materials and methods: Guided with online 1, 1-diphenyl-2-picrylhydrazyl (DPPH)-high-performance liquid chromatography (HPLC) screening,
antioxidants were first separated and isolated from the
ethanol extract of L. chinensis leaves by preparative-HPLC. Subsequently, offline DPPH approach was used to validate the
free radical scavenging activity of the components. Ultimately, the resulting
antioxidants were evaluated against the
hypoxia/reoxygenation (H/R)-, H2O2-, or
adriamycin (ADM)-induced injury in H9c2 cells to verify their cardioprotective effects in vitro. Results: Five
antioxidant ingredients, namely,
orientin,
isoorientin,
vitexin,
isovitexin, and
tricin, were quickly distinguished and isolated from L. chinensis leaves. The IC50 values of these ingredients were further examined by offline DPPH assay, as follows: 15.51±0.22, 6.64±0.38, 11.86±0.24, 8.89±0.66, and 31.86±0.24 μg/mL, respectively. Out of these ingredients,
isoorientin showed the strongest antioxidation, which was equivalent to that of the positive control drug (
vitamin C, IC50: 6.99±0.62 μg/mL). Using H/R-, H2O2-, and ADM-induced H9c2 cell injury models, the five ingredients had different extents of cardioprotective effects in vitro. In particular,
isoorientin showed the strongest protection. All the five ingredients also showed insignificant cytotoxic effect to normal H9c2 cells. Conclusion: The
ethanol extract of L. chinensis leaves contained five
antioxidants with low cardiac cytotoxicity.
Isoorientin possessed the strongest antioxidation, which can predominantly account for the myocardial protection effects within the extract.