Xanthohumol is a natural product found in the female of Humulus lupulus, also known as hops. This compound is also found in beer and belongs to a class of compounds that contribute to the bitterness and flavor of hops.
Biosynthesis
Xanthohumol is a prenylated chalconoid derived from a plant type III PKS, and is synthesized in the glandular trichromes of hop cones.
serves as the starting material, which is converted to
cinnamic acid by the PLP-dependent phenylalanine ammonia lyase.
Cinnamic acid is oxidized by cinnamate-4-hydroxylase and loaded onto
coenzyme A (CoA) by 4-coumarate CoA ligase to yield
Coumaroyl-CoA, the starter unit for PKS extension.
This molecule is extended three times with
Malonyl-CoA, cyclized through a Claisen condensation, and aromatized through
to form naringenin chalcone (chalconaringenin).
This intermediate has the potential to form a variety of different products depending on the enzymes that modify the core structure.
In the case of xanthohumol, a prenyltransferase called
Humulus lupulus prenyltransferase 1 (HlPT-1) attaches a molecule of dimethylallyl pyrophosphate from the DXP pathway.
HlPT-1 has a broad substrate specificity and also participates in making other prenylated flavonoids in the hop plant.
Finally, an O-methyltransferase methylates a phenol substituent using S-adenosyl methionine.
Total syntheses of xanthohumol and derivatives have been achieved, though extraction from hops remains a primary source.
Beer
In commercial beers, the concentration of xanthohumol ranges from about 2 μg/L – 1.2 mg/L.
During the
brewing process, xanthohumol and other prenylated flavonoids are lost as they are converted to the corresponding
.
Different hop varieties and different beers contain varying quantities of xanthohumol.
Research
Xanthohumol is under
basic research for its potential biological properties.
Xanthohumol can be
extract with pressurized hot water.
[A. Gil-Ramírez, J.A. Mendiola, E. Arranz, A. Ruíz-Rodríguez, G. Reglero, E. Ibáñez, F.R. Marín. [1] Highly isoxanthohumol enriched hop extract obtained by pressurized hot water extraction (PHWE). Chemical and functional characterization]. Innovative Food Science and Emerging Technologies 2012 October, vol 16 Pages 54-60. doi: 10.1016/j.ifset.2012.04.006.]
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See also
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Isoxanthohumol, the corresponding prenylated flavanone
-
8-Prenylnaringenin, a related prenylflavanoid with estrogenic activity
-
, a class of bitter compounds in hops
-
Myrcene, humulene, and caryophyllene, essential oils in hops
