A Cucurbitane Aldehyde from the Fruit Pulp of Momordica charantia
- PDF / 170,161 Bytes
- 4 Pages / 594 x 792 pts Page_size
- 92 Downloads / 179 Views
A CUCURBITANE ALDEHYDE FROM THE FRUIT PULP OF Momordica charantia
Chiy-Rong Chen,1 Yun-Wen Liao,2 Jue-Liang Hsu,2,3,4 Yun-Sheng Lin,5 and Chi-I Chang2,6,*
A cucurbitane triterpenoid, 7β-butoxy-3β-hydroxy-25-methoxycucurbita-5,23(E)-dien-19-al (1), was isolated from the fruit pulp of Momordica charantia. Structure determination of the new compound was accomplished by spectroscopic analyses including 1D and 2D NMR (1H, 13C, COSY, HMQC, HMBC, and NOESY) and EI-MS and comparison with the data of known analogues. Keywords: Momordica charantia, Cucurbitaceae, fruit, triterpenoid, cucurbitane. Bitter melon, Momordica charantia L. (Cucurbitaceae), is widely cultivated as a vegetable crop in many tropical and subtropical areas of the world, including Asia, Africa, and South America. It has extensively been used in folk medicine as a remedy for diabetes in Asia. Various types of biological activities such as cytotoxic, antidiabetic, and anti-inflammatory activities [1–4] have been reported for the crude extracts and compounds from this plant. More than 90 cucurbitane-type triterpenes have been isolated from its fruits [4–9], seeds [10–12], roots [13], vines [14–17], stems, and leaves [18, 19]. Our continuous interest in the secondary metabolites of Taiwanese M. charantia led to the isolation and structure elucidation of 30 cucurbitanetype triterpenoids from the MeOH extract of the stems [20–24] and fruit pulp of this plant [25, 26]. One more new cucurbitane-type triterpenoid, 7β-butoxy-3β-hydroxy-25-methoxycucurbita-5,23(E)-dien-19-al (1), was identified from the extracts of the fruit pulp of M. charantia (Fig. 1). Herein, the extraction, isolation, purification, and structure elucidation of the new compound is described. Compound 1 was obtained as a white powder and deduced to be a triterpenoid due to a positive Liebermann-Burchard test. Its molecular formula was determined as C35H58O4 from the 13C NMR data and an [M]+ ion at m/z 542.4338 in the HR-EI-MS, indicating seven indices of hydrogen deficiency. The IR spectrum showed absorption bands for hydroxy (3441 cm–1), (E)-configured double-bond (3055, 1656, 974 cm–1), and aldehyde (2855, 2746, 1711 cm–1) functionalities. The 1H and 13C NMR spectra of 1 (Table 1) displayed characteristic resonances of six tertiary methyls [δH 0.74, 0.90, 1.05, 1.24 (3H each, s), and 1.23 (3H × 2, s)], one secondary methyl [δH 0.89 (3H, d, J = 6.4 Hz)], a methoxy [δH 3.12 (3H, s); δC 50.3 (q)], a trisubstituted double bond [δH 5.90 (1H, dd, J = 1.2, 5.2 Hz); δC 122.6 (d), 145.6 (s)], and an (E)-configured double bond [δH 5.37 (1H, d, J = 15.6 Hz), 5.50 (1H, ddd, J = 5.6, 8.4, 15.6 Hz); δC 128.3 (d), 136.9 (d)]. With the aid of 1H–1H COSY, the resonances of a set of butoxyl group [δH 3.30, 3.36 (each 1H, m, H-1′), 1.48, (2H, m, H-2′), 1.30 (2H, m, H-3′), 0.87 (3H, t, J = 7.6 Hz, H-4′); δC 68.2 (t, C-1′), 32.0 (t, C-2′), 19.3 (t, C-3′), 13.9 (q, C-4′)] were assigned. In the 13C NMR spectrum, 35 carbon signals were observed, which were assigned by DEPT experiments as nine methyl, 10 methylene,
Data Loading...
