Gymnemic acid

Gymnemic acids are a class of chemical compounds isolated from the leaves of Gymnema sylvestre (Apocynaceae). They are anti-sweet compounds, or sweetness inhibitors.^[1] After chewing the leaves, solutions sweetened with sugar taste like water.

Chemically, gymnemic acids are triterpenoid glycosides. The central structure is the aglycone gymnemagenin (C₃₀H₅₀O₆).^[2] This is adorned with a sugar such as glucuronic acid and with various ester groups. These variations give rise to the different gymnemic acids.^[3] More than 20 homologs of gymnemic acid are known.^[4]

Gymnemic acid I has the highest anti-sweet properties. It suppresses the sweetness of most of the sweeteners including intense artificial sweeteners such as aspartame and natural sweeteners such as thaumatin, a sweet protein. The anti-sweet activity is reversible, but sweetness recovery on the tongue can take more than 10 minutes.^[5]

Example chemical structures

Gymnemic acids[5]
Chemical structure
Name	Gymnemic acid I	Gymnemic acid II	Gymnemic acid III	Gymnemic acid IV
R1	tigloyl	2-methylbutanoyl	2-methylbutanoyl	tigloyl
R2	acetyl	acetyl	H	H
CAS Number	122168-40-5	122144-48-3	122074-65-1	121903-96-6
PubChem ID	11953919	91617872	14264066	14264063
Chemical formula	C43H66O14	C43H68O14	C41H66O13	C41H64O13
Molar mass (g/mol)	806.98	809.00	766.97	764.95

See also

Other anti-sweeteners:

• Hodulcine, a dammarane-type triterpene glycoside from the leaves of Hovenia dulcis
• Lactisole, sodium 2-(4-methoxyphenoxy)propanoate
• Ziziphin, a triterpene glycoside, C₅₁H₈₀O₁₈
• Gurmarin