xanthohumol

Xanthohumol is a natural product found in the female inflorescences 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. Xanthohumol is a prenylated chalconoid, biosynthesized by a type III polyketide synthase (PKS) and subsequent modifying enzymes.

== Biosynthesis == Xanthohumol is a prenylated chalconoid derived from a plant type III PKS, and is synthesized in the glandular trichromes of hop cones. L-Phenylalanine 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 4-hydroxy-cinnamoyl CoA, the starter unit for PKS extension. This molecule is extended three times with malonyl CoA, cyclized through a Claisen condensation, and aromatized through tautomerization 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.