Since
flavonoids scavenge
reactive oxygen species, they may potentially protect against
ischemia/reperfusion injury. This study compared the scavenging capacity of specific
flavonoids towards different
reactive oxygen species. Whether the differential
oxidant scavenging capacity correlated with their protective efficacy in
ischemia/reperfusion injury of cardiomyocytes was determined. The
free radical scavenging capacity of five
flavonoids (
wogonin,
baicalin,
baicalein,
catechin and
procyanidin B2) was analyzed using electron spin resonance spectrometry for 3 radicals: 1,1-diphenyl-2picrylhydrazyl (DPPH),
superoxide and
hydroxyl radical. A well-established chick cardiomyocyte model of
ischemia (1 h)/reperfusion (3 h) was used to evaluate
flavonoid-induced protection against
ischemia/reperfusion injury in chronic treatment (pretreated 72 h and treated through
ischemia/reperfusion) and acute treatment protocols (during
ischemia/reperfusion or only at reperfusion). The cell viability was assessed by
propidium iodide. The DPPH scavenging was most significant with
catechin, followed by
procyanidin B2,
baicalein,
baicalin, and
wogonin. The
superoxide scavenging was, similarly, most significant with
catechin, followed by
baicalein,
procyanidin B2, and
baicalin. For
hydroxyl radical, only
baicalein showed a significant scavenging capacity (>50% reduction in ESR signal). For the cardiomyocyte studies, all
flavonoids but
wogonin showed protection against
ischemia/reperfusion injury in the chronic treatment protocol. When
flavonoids were administered only during
ischemia/reperfusion,
baicalein,
procyanidin B2, and
catechin significantly reduced cell death. If
flavonoids were administered just at reperfusion, only
baicalein and
procyanidin B2 had protective effects, and the efficacy was less.
Flavonoids possess specific but differential radical scavenging capacity, which, in conjunction with the timing of treatment, affects their protective efficacy in cardiomyocytes exposed to
ischemia/reperfusion.