BLBS102-c37 BLBS102-Simpson March 21, 2012 14:15 Trim: 276mm X 219mm Printer Name: Yet to Come
714 Part 6: Health/Functional Foods2-Phenyl-1,4-benzopyrone
(The basic backbone
structure of flavonoids)MyricetinOOH
OHOHOHOH
OHOHOHOH
OHHO B
AOOOHHO
AOBOOHHOB
O
AOOQuercetinKaempferolCatechinApigeninGenisteinNaringeninNaringinOOH OOH
O OOO
O
OH
OHOHOHOHOOHH 3 C
HOHOOHOOHHO
OHOHOHOOH OHOOHOHO OHOOHOHOOH OOHO OOOOOHOOHHOHOH 3 CHOHO OHOCH 3HOOCH 3HesperidinHesperetinFigure 37.7.Structures of common flavonoids.have a common core structure, the benzopyrone ring (Fig. 37.7),
which bears a structural resemblance to the flavylium ion of
anthocyanins or anthocyanidins (Fig. 37.6). Flavonoids are sub-
divided into five sub-classes: the flavanols, the flavanones, the
flavonols, the flavones, and the isoflavones. These five groups of
compounds exhibit subtle differences in structure, such as de-
gree of saturation or unsaturation, and/or position of substituent
groups (Fig. 37.7). Examples of the flavanols are catechin, epi-catechin, epigallocatechin, epicatechin gallate, epigallocatechin
gallate, and theaflavins; examples of the flavanones are butin,
hesperidin, hesperetin, naringenin and naringin; the flavonols
include azaleatin, quercitin, kaempferol, myricetin, morin, and
rhamnetin; members of the flavones family include apigenin,
baicalein, chrysin, luteolin, tangeritin, and wogonin; and the
isoflavones are typified by daidzein, genistein, and glycitein.
The flavonoids have lower coloring power compared with the