Identification of Terpene Lactones and Flavonol Glycosides in Preparations Based on Ginkgo Biloba Extract and a New Way of Semi-Quantitative Determination of Flavonol Glycosides by 1H NMR Spectroscopy

Abstract

The composition of terpen lactones and flavonol glycosides of commercial preparation series based on Ginkgo biloba extracts was investigated by ¹H NMR spectroscopy. The content of individual terpen lactones was determined using DMSO-d₆ and acetone-d₆ solvents. The effect of the structure of flavonol glycosides on the signal of the hydroxyl proton at a position 5 of the ring A was examined. A new approach was proposed for semiquantitative determination of the total amount of flavonol glycosides by the integral intensity of this signal, which is a superposition of the singlets in the region of 12.5–12.65 ppm of individual flavonoids in DMSO-d₆. Since the corresponding signals of aglycones (quercetin, kaempferol, isorhamnetin), which are minor components of the Ginkgo biloba extracts, appear separately in a slightly different region (12.45–12.48 ppm), the proposed method can also be used for detecting adulteration of Ginkgo biloba extracts by means of the addition into them of relatively cheap aglycones or rutin as well as for assessment of the content of flavonoids of similar structure in some types of plant raw materials.