Reinvestigation of Phenolic Glycosides of Solanum Glaucophyllum Desf.

The current study is primarily aimed at reinvestigating the flavonoid glycoside composition of Solanum glaucophyllum Desf. (SG). Only a few substances were described in the literature. The analysis of glycosidic compounds of SG is a focus of interest to improve the understanding of glycosylation patterns. Probably these results will help in isolation and determination of 1,25-dihydroxycholecalciferol (1,25(OH)2D3) derivatives. Up to now, only two glycosides of 1,25(OH)2D3 were discussed in the literature while a much more complex situation is expected. We have discovered in SG via size-exclusion chromatography, up to more than 10 sugar units could be bound.

Acidic hydrolyses of a crude leaf extract (acetone/water) and subsequent analyses by HPLC-DAD revealed that almost solely quercetin derivatives were present in SG (>95%). Preparative reverse phase chromatography using water/methanol as mobile phase allowed isolation of 3 pure flavonoid-glycosides that were unequivocally identified as isoquercitrin (A), rutin (B) and quercetin-3-O-apiosylrutinoside (C) via HRMS and 1D-/2D-NMR. All structures were known from the literature and occurred in a ratio of 0.4/1.0/0.4 (A/B/C). Moreover, small amounts (<5% of total flavonoids at 350 nm) of more polar quercetin derivatives were observed. One of them is supposed to be quercetin-3-O-rutinoside-7-O-glucoside (D) which is described for the first time in SG ([Fig. 1]).

Fig. 1 HPLC-DAD chromatogram of Solanum glaucophyllum extract at 350 nm.

In summary, glycosylation of quercetin in SG is solely based on glucose, rhamnose and apiose. This finding will help in the determination of the more complex glycosidic pattern of 1,25(OH)2D3.

Conflict of Interest SA is an employee of Herbonis. Funding This project was funded by Herbonis.

 

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Artikel online veröffentlicht:
16. November 2023