Influence of extraction methods on stability of flavonoids.

The LC-MS/MS was applied for the determination of flavonoids' stability under four types of solvent extraction methods (reflux heating, sonication, maceration and microwave) from maize samples. The 11 flavonoids belong to different groups: flavonols (kaempferol, myricetin, rhamnetin, quercetin, rutin), flavanones (naringenin, naringin, hesperedin), flavones (apigenin, luteolin), isoflavones (genistein) were studied. The effect of the degradation of flavonoids depended on extraction mode and chemical structure. The smallest decomposition was observed by heated reflux extraction procedure within 30 min in water bath and by microwave assisted extraction under 160 W during 1 min. The decomposition for flavonoids depends on number of substituents in flavonoid molecule. The most unstable compound (recovery below 50%) in tested condition was myricetin. The higher number of hydroxyl groups promote degradation of flavonoids, whereas sugar moiety and methoxyl groups protect flavonoids of degradation during microwave and ultrasonic assisted extraction.