Abstract: Fallen leaves of hawthorn(Crataegus maximowiczii Schneid.) in autumn was used as raw material to extract flavonoids by 70% ethanol as solvent after treated by microwave irradiation. Yield of flavonoids was measured by using rutin as standard substance. Extraction conditions of flavonoids from hawthorn leaves assisted by microwave were investigated through experiments. The results showed that the extraction conditions were as follows: granularity of hawthorn leaves 0.212～0.55mm, microwave irradiation power 210 W, irradiation time 15min, ratio of material to solvent 1:10, extracting for 4 times under 75℃ and 0.5:h each time. Average yield of flavonoids from hawthorn leaves was 8.38%(as rutin) and relative standard deviation was 1.14%, indicating a good repeatability. Average yield of flavonoids of extraction assisted by microwave was 1.13% higher than that of traditional method. Therefore, microwave irradiation is favorable to extraction of flavonoids from hawthorn leaves.

Key words: hawthorn leaves, microwave, flavonoids