Journal of Asian Natural Products Research
5
MeOH–H2O (7:3:0.5) to give 5 (60 mg).
Fr.4 (6 g) was applied to silica gel
(CHCl3 –MeOH–H2O, 7:3:0.5–6:4:1)
and MCI gel CHP-20P (MeOH–H2O,
1:1–1:0) CC to afford 6 (6 mg) and 7
(12 mg). Fr. 5 (69 g) was separated by
repeated CC over silica gel (CHCl3–
MeOH–H2O, 6:4:1), RP-8 (40–80%
MeOH), and Sephadex LH-20 (5–40%
MeOH) to yield 2 (22 mg) and 4 (2 g).
1.81 (br d, J ¼ 14.5 Hz, H-7a), 1.91-1.92
(m, H-25), 2.00 2 2.03 (2 H, m, H-1b,
24b), 2.05 2 2.06 (m, H-23b), 2.20 2 2.22
(m, H-20), 2.39 (br t, J ¼ 12.1 Hz, H-4a),
2.63 (br d, J ¼ 12.1 Hz, H-4b), 3.56 2 3.60
(m, H-26), 4.73 (d, J ¼ 7.7 Hz, H-26-Glc-1),
4.87 (d, J ¼ 7.8 Hz, H-Gal-1), 4.92
(q, J ¼ 7.2 Hz, H-16), 5.14 (d, J ¼ 7.6 Hz,
H-Glc II-1), 5.15 (d, J ¼ 7.4 Hz, H-Glc I-1),
5.25 (d, J ¼ 7.8 Hz, H-Xyl-1), 5.27
(br s, H-6), 5.55 (d, J ¼ 7.2 Hz, H-Glc
III-1). 13C NMR (pyridine-d5, 400MHz)
(negative ion mode): m/z 1374 [M]2, 1242
[M 2 132]2, 1212 [M 2 162]2, 1080
[M 2 132 2 162]2, 1050 [M 2 162 2
162]2, 918 [M 2 132 2 162 2 162]2,
755[M 2 132 2 162 2 162 2 162 2 H]2,
431 [M 2 132 2 162 2 162 2 162 2
162 2 162 2 H]2. HRESI-MS (negative
ion mode): m/z 1373.6257 [M 2 H]2
(calculated for C62H101O33, 1373.6225).
3.3.1. Pratioside G (1)
White amorphous powder, [a]D 294.9 (c
0.12, MeOH). IR ymax (KBr) 3440 (OH),
1675 and 1635 (a, b-unsaturated ketone)
cm21. 1H NMR (pyridine-d5, 500 MHz): d
0.91 (s, CH3-18), 0.96 (d, J ¼ 6.7 Hz,
CH3-27), 1.10 (s, CH3-19), 1.34 (d,
J ¼ 6.8 Hz, CH3-21), 1.47-1.49 (2 H, m,
H-9, 14), 1.91 (2 H, m, H-25, 17), 2.20-
2.23 (m, H-20), 2.46 (t, J ¼ 10.8 Hz, H-8),
2.62 (br t, J ¼ 11.0 Hz, H-4a), 2.71 (br d,
J ¼ 11.0 Hz, H-4b), 3.29-3.31 (m, H-15),
3.58-3.60 (m, H-26a), 3.82-3.84 (m, H-
Glc-5), 3.86-3.89 (m, H-3), 3.92–3.95 (m,
H-26b,), 4.00-4.03 (m, H-Glc-2), 4.19 (t,
J ¼ 8.8 Hz, H-Glc-3), 5.85 (s, H-6), 4.81
(d, J ¼ 7.7 Hz, H-Glc-1), 4.22 (H, t,
J ¼ 8.8 Hz, H-Glc-4), 4.39-4.41 (m, H-
Glc-6a), 4.55 (br d, J ¼ 8.6 Hz, H-Glc-6b).
13C NMR (pyridine-d5, 400 MHz) spectral
data: see Table 1. FAB-MS (negative ion
mode): m/z 607 [M 2 H]-, 445
[M 2 162 2 H]2. HRFAB-MS (negative
ion mode): m/z 607.3486 [M 2 H]2
(calculated for C33H51O10, 607.3482).
3.4. Acid hydrolysis of 2
Compound 2 (10 mg) dissolved in 2 M
HCl–dioxane (1:1, 4 ml) was hydrolyzed
at 958C for 6 h. After cooling to room
temperature, 2 ml H2O was added into the
reaction mixture, then extracted with
CHCl3 (6 ml £ 3). The CHCl3 phase was
identified as diosgenin by comparing with
authentic sample on TLC. The aqueous
layer was treated using the method as
described in reference [14], and the
absolute configurations of monosacchar-
ides were determined to be D-galactose,
D-glucose, and D-xylose respectively, on
the basis of GC analysis of their
derivatives.
3.3.2. Pratioside H (2)
White amorphous powder, [a]D 253.0
(c 1.09, MeOH). 1H NMR (pyridine-d5,
500 MHz): d 0.85 (s, CH3-18), 0.86 (s,
CH3-19), 0.87 2 0.89 (m, H-9), 0.96
(d, J ¼ 6.4 Hz, CH3-27), 1.01-1.03 (m,
H-14), 1.08 2 1.09 (m, H-12a), 1.32 (d,
J ¼ 6.3 Hz, CH3-21), 1.47 2 1.49 (m,H-11),
1.64 2 1.67(2 H, m, H-1a, 24a), 1.68 2 1.70
(m, H-23a), 1.71 (br d, J ¼ 7.7 Hz, H-12b),
Acknowledgments
The authors are grateful to members of the
Analytical Group in State Key Laboratory of
Phytochemistry and Plant Resources in West
China, Kunming Institute of Botany, for
measurements of all spectra. This work was
financially supported by the 973 Program of
Ministry of Science & Technology of China