Hesperidin
Hesperidin is a flavanone glycoside found in citrus fruits. Its aglycone form is called hesperetin. Its name is derived from the word "hesperidium", for fruit produced by citrus trees. Hesperidin was first isolated in 1828 by French chemist Lebreton from the white inner layer of citrus peels (mesocarp, albedo). Hesperidin is believed to play a role in plant defense. Sources. Section::::"Lamiaceae". Peppermint contains hesperidin. Content in foods. Approximate hesperidin content per 100 ml Metabolism. Hesperidin 6-O-alpha-L-rhamnosyl-beta-D-glucosidase, an enzyme that uses hesperidin and HO to produce hesperetin and rutinose, is found in the  Ascomycetes species. Research. As a flavanone found in the rinds of citrus fruits (such as oranges or lemons), hesperidin is under preliminary research for its possible biological properties in vivo. One review did not find evidence that hesperidin affected blood lipid levels or hypertension. Another review found that hesperidin may improve endothelial function in humans, but the overall results were inconclusive. Biosynthesis. The biosynthesis of hesperidin stems from the phenylpropanoid pathway, in which the natural amino acid L-phenylalanine undergoes a deamination by phenylalanine ammonia lyase to afford ("E")-cinnamate. The resulting monocarboxylate undergoes an oxidation by cinnamate 4-hydroxylase to  afford ("E")-4-coumarate, which is transformed into ("E")-4-coumaroyl-CoA by 4-coumarate-CoA ligase. ("E")-4-coumaroyl-CoA is then subjected to the type III polyketide synthase naringenin chalcone synthase, undergoing successive condensation reactions and ultimately a ring-closing Claisen condensation to afford naringenin chalcone. The corresponding chalcone undergoes an isomerization by chalcone isomerase to afford (2"S")-naringenin, which is oxidized to (2"S")-eriodictyol by flavonoid 3’-hydroxylase. After "O"-methylation by caffeoyl-CoA "O"-methyltransferase, the hesperitin product undergoes a glycosylation by flavanone 7-"O"-glucosyltransferase to afford hesperitin-7-"O"-β-D-glucoside. Finally, a rhamnosyl moiety is introduced to the monoglycosylated product by 1,2-rhamnosyltransferase, forming hesperidin