Application of Standard Addition Method in the Spectrophotometric Determination of Flavonoids in Mulberry Leaves

[Objective] The aim was to study the determination methods of flavonoids in mulberry leaves and optimize the determination condition.[Method] With water as extractant,the flavonoids were extracted in boiling bath for 5 min.The total quantity of flavonoids in mulberry leaves was determined by NaNO2-Al(NO3)3-NaOH spectrophotometry and the standard addition method was applied into the determination operation to optimize the determination condition.[Result] The single factor experiments showed that when the addition of 60% ethanol was 0～11 ml,the dose of NaNO2 was 0.50～2.00 ml,the dose of Al(NO3)3 was 0.75～2.00 ml or the dose of NaOH was 1.50～5.00 ml,the differences on absorption value among colored solutions were little and that induced by extraction time was little,too.But when Al(NO3)3 was too much excessive,the stability of colored solution became worse.When the dose of NaOH was less than 3.00 ml,the coloring reaction was slower.[Conclusion] Determination of flavonoids in mulberry leaves by standard addition method could avoid the circumstance that the flavonoids couldn't be determined normally due to too much consumption of tested sample solution.The method of extraction with ratio of sample to water being 1∶100 and in boiling bath for 5 min could extract the most flavonoids from the grinded mulberry leaves.