Analysis and assay of flavonoid content in the vegetative and reproductive organs of the showy tick trefoil

We report here a many-year study of the qualitative and quantitative content of flavonoids in the reproductive organs of the showy tick trefoil (Desmodium canadense (L.) DC., Fabaceae) - stems, leaves, buds, inflorescences,pods, and seeds - collected at different phases of growth at the Department of Medicinal Plants, Kaunas Botanical Garden, Vytautas Magnus University. HPLC studies identified 15 aglycone and glycoside flavonoids: apigenin, apigenin-7-O-glycoside, luteolin, rutin, vicenin-2, vitexin, isovitexin, vitexin rhamnoside, orientin, homoorientin, quercetrin, quercetin, hyperoside, astralagin, and kaempferol. The largest quantities of flavonoids in the vegetative organs from year 2 to year 4 of plant growth were present in the leaves (2.64% and 2.61% at budding and flowering in the second year respectively), while during year 5 maximum quantities were present during budding, flowering, and the beginning of fruiting, during year 6 in budding, and during year 7 during regrowth and budding. In stems, the greatest flavonoid quantities accumulated during the second year of growth during budding and flowering (up to 0.61%). In the reproductive organs, the maximum quantities of flavonoids accumulated in the inflorescences during years 3 – 6 of growth, reaching 2.37% in the flowering phase in year 6. Thus, not only the herb part, but also the leaves of the showy tick trefoil can be used as raw material for herbal remedies. The optimum time for collecting leaves is during flowering, the onset of fruiting, and budding of regrowth after mowing, and the plantation lifetime is seven years.