Stable Isotope Dilution Analysis of the Major Prenylated Flavonoids Found in Beer, Hop Tea, and Hops

Abstract

Prenylated flavonoids from hops (Humulus lupulus) have become of interest in recent years due to a range of bioactivities. The potential health benefits of prenylated flavonoids include anti-cancerous activities and treatment of the metabolic syndrome among others. Since prenylated flavonoids from hops have shown pharmaceutical potential in clinical trials, robust analytical methods to determine their concentrations in food, supplements, and beverages are required. One such, the gold standard of analytical methods, is stable isotope dilution analysis due to its ability to compensate matrix effects and losses during sample work-up. As no commercial standards were available, the synthesis of seven different prenylated flavonoid isotopes utilizing various strategies (microwave assistance, acid base catalyst in the presence of deuterated substance and lastly, the use of Strykers catalyst) is described. The produced prenylated flavonoid isotopes were then applied in the first stable isotope dilution analysis method that quantified six natural prenylated flavonoids (Isoxanthohumol, Isoxanthohumol-C, 8-Prenylnaringenin, 6- Prenylnaringenin, Xanthohumol, and Xanthohumol-C) in beer, hop tea and hops to prove its applicability. The SIDA-LC-MS/MS method was validated resulting in LODs and LOQs for all analytes between 0.04 and 3.2 μg/L. Moreover, due to the simple clean-up the developed method allows the prospect for measuring clinical samples in the future.

The Potent Phytoestrogen 8-Prenylnaringenin: A Friend or a Foe?

“…Polyclonal antibodies were used for the design of a radioimmunoassay (RIA), and monoclonal for devising an enzyme-linked immunosorbent assay (ELISA) [ 33 , 34 ]. The most recent new technique described for 8-PN quantification is stable isotope dilution analysis (SIDA) [ 16 ].…”

“…For example, in a study reported by Stevens and Page (2004) [ 9 ], European lager was found to contain a mere 1 µg/L, whereas American porter possessed a concentration of 240 µg/L. Still, in people harboring high intestinal and/or hepatic biotransformation capacities (see 8-PN pharmacokinetics), the ultimate source of 8-PN is, in most cases, IX, because its concentration in beer exceeds that of 8-PN by 10–40-fold [ 9 , 15 , 16 ]. Assuming the consumption of 1 L of, for example, “imported stout” beer with 8-PN and IX concentrations of 69 and 2100 µg/L, respectively [ 15 ], a person endowed with efficient conversion capability (80%; [ 17 ]) would be exposed to ~1700 µg 8-PN.…”

“…Apart from hops, the occurrence of 8-PN has been reported in at least 21 ethnomedicinally applied plants [ 20 ], including citrus plants [ 21 ]. It may also occur in herb or hop teas at low concentrations (<10 µg/L); IX concentrations seem to be only slightly higher in these products (<15 µg/L) [ 15 , 16 ].…”

Exploration of Antimicrobial Ingredients in Psoralea corylifolia L. Seed and Related Mechanism against Methicillin-Resistant Staphylococcus aureus

“…Based on previous studies, we knew that most of the flavonoids in PCSs are IPFs [ 12 ]. Compared with common flavonoids, isopentenyl flavonoids have special UV absorption and mass spectrometry pyrolysis [ 17 , 18 ]. Therefore, we can quickly pick them out by identifying their characteristic cleavage peaks.…”

Synthesis of xanthohumol and xanthohumol-d3 from naringenin

“…15,16 Deuterated compounds are also considered as attractive drug candidates due to the inuence of the kinetic isotope effect on pharmacokinetics. [17][18][19] Although approaches to 13 C-enriched xanthohumol 20,21 and hydrogen/ deuterium exchange in 1a 22 were reported, no scalable and cost-effective synthesis of the deuterium-labeled derivative of 1a (i.e. 1b) has been disclosed to date.…”