Quantitative hplc estimation of flavonoids in showy tick trefoil (Desmodium canadense) herbs

Quantitative and qualitative analyses of flavonoids in showy tick trefoil (Desmodium canadense L., Fabaceae) herbs during various vegetative phases were performed using HPLC techniques at the Department of Medicinal Herbs of the Kaunas Botanical Garden (Vytautas Magnus University). A total of 15 flavonoids of aglycone and glycoside nature was determined including apigenin, apigenin-7-O-glycoside, luteolin, rutin, 2-vicenin, vitexin, isovitexin, vitexin rhamnoside, orientin, homoorientin, quercitrin, quercetin, hyperoside, astragalin, and kaempferol. The maximum amount of identified flavonoids was observed during the flowering phase and was 2.45% in the second vegetative year and 1.28% in the sixth vegetative year, i.e., it decreased constantly during the plant perennial vegetation process. Of these, orientin and homoorientin varied from 45.9 to 38.9% of the total flavonoids; 2-vicenin, from 16.3 to 12.8; vitexin, from 12.7 to 8.6; isovitexin, from 13.0 to 7.7; rutin, from 11.6 to 6.9. The optimum collection time of showy tick trefoil herbs as plant raw material was the flowering and budding phases of herbs regrowing after mowing. The recommended optimal exploitation time of a plantation is up to six years.