The Use of Spectroscopic Methods for Structural Elucidation of Individual Secondary Metabolites Isolated from the Aerial Parts of Corydalis bracteata

Plants of the Corydalis (Papaveraceae) genus are widely used in oriental medicine and are known for their particularly rich content of biologically active substances. One of the species encountered in Russia, the large-flowered corydalis (Corydalis bracteata (Steph. ex Willd.) Pers.), is widespread in Western and Eastern Siberia, but none the less its chemical composition has not been properly studied yet.

The aim of the study was to perform phytochemical analysis of Corydalis bracteata herb through isolation of the main secondary metabolites and elucidation of their structure, using modern chromatographic methods of analysis and NMR spectroscopy.

Materials and methods: the analysis was performed for dried aerial parts of C. bracteata. The isolation of individual compounds was performed using open-column chromatography and glass columns packed with sorbents with different selectivity characteristics— Dianion^® HP-20 (Supelco) and Sephadex® LH-20 (GE Healthcare)—as well as preparative-scale chromatography with a Kromasil^® C18 column and detection at 235 nm. Water and acetonitrile mixed in the ratios 5:95–50:50 v/v with the addition of 0.1% trifluoroacetic acid were used as the eluents. The analysis of fractions before pooling was performed by high-performance thin-layer chromatography with Silica gel 60 F₂₅₄ plates (Merck). The analysis of the individual compound solutions was performed by HPLC using a Prominence LC-20 (Shimadzu) instrument, a SUPELCOSIL™ LC-18 column, and detection at 235 nm. The structures of the isolated individual compounds were elucidated by one- and two-dimensional NMR spectroscopy using a Bruker Avance III 400 MHz NMR spectrometer.

Results: four individual compounds from the С. bracteata aerial parts were isolated and analysed: an isoquinoline alkaloid— coptisine (1) and three flavonoids—rutin (2), quercetin-3-O-β-D-glucopyranoside (3), and kaempferol-3-O-β-D-glucopyranoside (4).

Conclusions: as a result of the phytochemical analysis of the С. bracteata aerial parts, compounds of both alkaloid and flavonoid nature were isolated for the first time, and their structures were elucidated using NMR spectroscopy. С. bracteata should be considered as a promising potential source of biologically active substances.

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