154
N. N. Win and H. Morita
Fig. 17 Structures of fatty
acid derivatives 92–95
isolated from ethanol and
acetone extracts of E. scaber
O
O
92 (ethyl hexadecanoate)
O
O
93 (ethyl-9,12-octadecadienoate)
94 (ethyl-(Z)-9-octadecenoate)
O
O
95 (ethyl octadecanoate)
O
O
Fig. 18 Structures of
triterpene 96 and sterols 97
and 98 isolated from ethanol
and acetone extracts of E.
scaber
HO
96 (lupeol)
97 (stigmasterol)
HO
98 (stigmasterol glucoside)
O
O
HO
HO
OH
OH
and iso-17,19-dihydrodeoxyelephantopin (90) [87] (Fig. 16), a known sesquiterpene lactone, deoxyelephantopin (91) [88] (Fig. 16), four fatty acid derivatives,
ethyl hexadecanoate (92) [89], ethyl-9,12-octadecadienoate (93) [90], ethyl-(Z)-9octadecenoate (94) [91], and ethyl octadecanoate (95) [92] (Fig. 17), the triterpene
lupeol (96) [93], and two sterols, stigmasterol (97) [94] and its glucoside 98 [94]
(Fig. 18), were isolated from ethanol and acetone extracts of the whole plants of
E. scaber. Among these, 17,19-dihydrodeoxyelephantopin (89) is an epimer of iso17,19-dihydro-deoxyelephantopin (90) at C-2. In turn, deoxyelephantopin (91) is
a structural analog of 17,19-dihydrodeoxyelephantopin (89) with a methacryloxy