Quantitative determination of flavonoids from the aerial part of greater knapweed (Centaurea scabinosa L.)

Quantitative determination of flavonoids from the aerial part of greater knapweed (Centaurea scabiosa L.) has been carried out by differential spectrophotometry in combination with a modified method of forming flavonoid complexes with aluminum chloride in HCl. Depending on the plant collection site, the quantitative content of flavonoids in the aerial part of greater knapweed varied within 1.3 - 2.0% (calculated as rutin). The random error of measurement did not exceed 3% at a confidence probability of 0.95. The systematic error of the proposed metohd did not exceed the error of determination. The accumulation dynamics of flavonoids in the aerial part of greater knapweed during the 2006 vegetative peroid have been tracked for plants growing in Tomsk and Kemerovo regions. The maximum content of flavonoids (1.70 ± 0.04% calculated as rutin) was observed in the stage of full flowering, which is therefore the optimum period for collecting the aerial part of the plants for the maximum yield of flavonoids. The maximum amount of flavonoids was accumulated in leaves (1.96 ± 0.04%), which is somewhat greater than the content of flavonoids in the entire aerial part of greater knapweed (1.70 ± 0.04%).