Natural Products in Food, Spices, and Beverages - Natural Products Chemistry: Sources, Separations, and Structures - page 146

OH

HO OH

OH OH

FIGURE 13.1 Chemical structure of xylitol.

O

O OCH 3

H

OH NH 2 O

FIGURE 13.2 Structure of the sweetener aspartame.

HO

OH

HO

CI

O CI

O

HO O

OH

CI

FIGURE 13.3 Structure of sucralose.

known as sweetleaf, is widely grown for its sweet leaves. Stevia's taste has a slower
onset and longer duration than that of sugar, although some of its extracts may have
a bitter or licorice-like aftertaste at high concentrations.
The steviol glycoside extracts have up to 300 times the sweetness of sugar. The
tongue's taste receptors react to the glucose in the glycosides; those with more glucose
(rebaudioside) taste sweeter than those with less (stevioside). Some of the tongue's
bitter receptors react to the aglycones. Further, in the digestive tract, rebaudiosides
are metabolized into stevioside. Then stevioside is broken down further into glucose
and steviol. The glucose released in this process is used by bacteria in the colon and
is not absorbed into the bloodstream. Steviol cannot be further digested and is passed
out from the digestive system in the urine or feces.

13.6 LICORICE
Glycyrrhizin (also known as glycyrrhizic acid or glycyrrhi zinic acid) is the main
sweet-tasting compound from licorice root and is 30 to 50 times as sweet as sucrose