Flavonoids from Malus hupehensis and their cardioprotective effects against doxorubicin-induced toxicity in H9c2 cells

Three biflavonoid glycosides along with 12 known flavonoids, were isolated from leaves of Malus hupehensis. The complete structures of two of the compounds were established from analysis of MS, NMR spectroscopic and CD data, as well as DFT CD calculations they were determined to be atropisomeric along a central biaryl axis. The antioxidant activities and protective effects of the compounds against doxorubicin-induced cardiomyopathy in H9c2 cells were also investigated. Amongst all of the isolated compounds, quercetin was the most active radical scavenger with EC(50) values of 3.2 μM and 17.8 μM by the DPPH and ABTS(+) methods, respectively. The results indicated that three of the flavanoids also had a strong protective influence against doxorubicin-induced cell death with EC(50) values of 8.3, 5.2 and 7.6 μM, respectively.