Gymnemic acids structure

H. M. Lui, F. Kiuchi, and Y. Tsuda, Isolation and structure elucidation of gymnemic acids, antisweet principles of Gymnema sylvestre, Chem. Pharm. Bull. (Tokio), 40 (1992) 1366-1375. 

Figure 2. Structure of gymnemic acid A, (III), the most abundant gymnemic acid.

Gymnemagenin and Gymnestrogenin. Gymnemagenin (1), mp 328-335°C,the major sapogenin from G. sylvestre was obtained by hydrolysis of gymnemic acid mixture by y -glucuronidase followed by alkaline hydrolysis. Its structure was elucidated to be 1/9,16/ , 21/3,22k, 23,28-hexahydroxyolean-.12-ene... 

A recent review by Kurlhara deals with structures and physiological action of sweetness-masking substances such as gymnemic acids, ziziphin, heat-stable sweet protein, mabinlins and taste converting protein from sourness to sweetness such as miraculins and curculins. 

Structures of compounds 87-148 are shown in the text. b Potency compared with gymnemic acid I (90) (x I). 

Since the initial reports of sweetness-inhibitory oleanane-type gymnemic acids from the leaves of Gymnema sylvestre, plant species of the family Asclepiadaceae have served as bountiful sources of sweetness-inhibitory compounds. The initial isolation and structural characterization of these compounds was very challenging, and these early investigations have been reviewed [19]. In 1989, gymnemic acids I-VI (90-95) were isolated with a common gymnemagenin (149) aglycone structure and a... 

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