¹³C-Labelling of Xanthohumol in Hop Cones (Humulus lupulus)

Abstract

Biolabelling conditions in hop cones of xanthohumol (Xn) were studied by feeding [U-¹³C]glucose, [1-¹³C]glucose, [ring-¹³C₆]phenylalanine, [2-¹³C]sodium acetate or [2-¹³C]malonic acid as biosynthetic precursors to hop sprouts. Quantitative ¹³C-NMR spectroscopic analysis of the resulting labelled Xn showed different labelling patterns and ratios depending on precursor and feeding concentrations. The highest incorporation rate was achieved with [U-¹³C]glucose (9.41 ± 1.22 %). With [ring-¹³C₆]phenylalanine only ring B was labelled (3.51 ± 0.08 % enrichment). [2-¹³C]sodium acetate and [2-¹³C]malonic acid allowed labelling of the A-ring (1.82 ± 0.02 % and 1.74 ± 0.03 % enrichment). The specific labelling pattern of the prenyl side chain with [1-¹³C]glucose (2.36 ± 0.27 % enrichment) confirmed the biosynthetic origin to be MEP pathway-derived. On the basis of these results radiolabelling of Xn will be performed for in vivo bioavailability studies.

Key words

Xanthohumol - hops - Humulus lupulus - Cannabinaceae - biolabelling - biosynthesis

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