Licorice root. A natural sweetener and an important ingredient
in Chinese medicine*
Isao Kitagawa
School of Pharmaceutical Sciences, Kinki University,
3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan
Abstract: This paper reviews our investigations on
the chemical constituents of several kinds of botanically identified
licorice roots, which led to the characterization of 13 then-new glucuronide-saponins
named licorice-saponins (AL), apioglycyrrhizin, and araboglycyrrhizin,
together with glycyrrhizin and 18a-glycyrrhizin
and also of 49 kinds of phenolic compounds and their glycosides (11
then-new). The restoration-promoting activity of licorice-saponin B2
for CCl4-intoxicated hepatocyte function and the structuresweetness
relationship of saponins were discussed. Biologically interesting, but
isolable in minor quantities, several licorice-saponins were favorably
synthesized from abundantly available glycyrrhizin. With 15 saponins
and 49 phenolic compounds (including their glycosides) at hand, chemical
evaluation of licorice root processings was undertaken. It was shown
that the cortex contained a rich amount of phenolic compounds, whereas
the xylem was rich in phenolic glycosides and the saponins contained
were richer in the xylem than in the cortex. It was also found that
roasted licorice root contained an increased amount of glycyrrhetic
acid monoglucuronide, which was secondarily formed from glycyrrhizin
through thermal hydrolysis and was known to taste 5 times sweeter than
glycyrrhizin.
* A special topic issue on the
science of sweeteners.
** Corresponding author.
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