New cycloartane and flavonol glycosides from Corchorus depressus

Article abstract of DOI:10.1002/1522-2675(200202)85:2<689::AID-HLCA689>3.0.CO;2-V

Two new monodesmosidic cycloartane triterpene glycosides, depressosides E and F, and two new flavonol glycosides, depressonol A and B, were isolated from the butanol-soluble part of the EtOH extract of Corchorus depressus L. The structures of the new comp

Full text of DOI:10.1002/1522-2675(200202)85:2<689::AID-HLCA689>3.0.CO;2-V

Helvetica Chimica Acta Vol. 85 (2002)
689
New Cycloartane and Flavonol Glycosides from Corchorus depressus
by Muhammad Zahida), Akbar Alib), Omar Ishurda), Amir Ahmedb), Zulfiqar Ali, Viqar Uddin Ahmadb),
and Yuanjiang Pan*a)
a) Department of Chemistry, Zhejiang University, Hangzhou 310027, P.R. China
b) HEJ Research Institute of Chemistry, International Center for Chemical Sciences, University of Karachi
75270, Pakistan
Two new monodesmosidic cycloartane triterpene glycosides, depressosides E and F, and two new flavonol
glycosides, depressonol A and B, were isolated from the butanol-soluble part of the EtOH extract of Corchorus
depressus l. The structures of the new compounds were elucidated as (22R,24S)-22,25-epoxy-9,19-cyclo-
lanostane-3b,16b,24-triol 3-[a-l-rhamnopyranosyl-(1 ! 4)-b-d-glucopyranoside] (1), (22R,24S)-22,25-epoxy-
9,19-cyclolanostane-3b,16b,24-triol 3-[a-d-glucopyranosyl-(1 ! 3)-b-d-glucopyranoside] (2), kaempferol 3-[b-
d-glucopyranosyl-(1 ! 4)-b-d-galactopyranoside] 7-[a-l-arabinofuranoside] (4), and kaempferol 3-[b-d-gluco-
pyranosyl-(1 ! 6)-b-d-galactopyranoside] 7-[a-l-arabinofuranoside] (5) on the basis of chemical evidence and
detailed spectroscopic studies.
Introduction. Corchorus depressus l., belonging to the family Tiliaceae, is a
medicinal plant growing wild in sandy, clayey, and saline areas of Pakistan [1]. It is
commonly known as −bhauphali× and has been used in folk medicine in the subcontinent
[2]. Previous phytochemical investigations of this species have led to the isolation of
flavonoids, a-amyrin derivatives, and cycloartane-type glycosides [3 6]. Our re-
investigation of the chemical constituents of C. depressus led to the isolation and
structure elucidation of two new cycloartane triterpene saponins, depressosides E (1)
and F (2), and two new kaempferol glycosides, depressonols A (4) and B (5), in
addition to the already reported compounds from this species.
Results and Discussion. The EtOH extract of the whole plants of Corchorus
depressus was partitioned into hexane-, AcOEt-, BuOH-, and H2O-soluble fractions.
The BuOH extract was subjected to vacuum liquid chromatography (VLC; silica gel),
column chromatography (Sephadex LH-20), and reversed-phase flash chromatography
(FC) to yield two fractions, each containing two compounds. Further purification by
HPLC afforded the two saponins, depressosides E (1) and F (2) and the two flavonol
glycosides, depressonols A (4) and B (5) in pure form.
Depressoside E (1) was isolated as an amorphous powder. The positive-ion FAB-
‡
MS of 1 exhibited quasi-molecular ion peaks at m/z 805 ([M ‡ Na] ) and 783 ([M ‡
‡
H] ), corresponding to the molecular formula C42H70O13 for 1. The fragment ions at
m/z 659 and at 497indicated the presence of two sugar units, one hexose and one
deoxyhexose, in the molecule. The presence of two sugars in the molecule of 1 was also
confirmed by the negative-ion FAB-MS. The assignments of all the 1H- and 13C-NMR
1
signals of 1 were successfully carried out with H,1H COSY, HMQC, and HMBC
experiments (Table 1). Thus, depressoside E (1) was identified as (22R,24S)-22,25-

690
Helvetica Chimica Acta Vol. 85 (2002)
epoxy-9,19-cyclolanostane-3b,16b,24-triol 3-[a-l-rhamnopyranosyl-(1 ! 4)-b-d-gluco-
pyranoside].
The 1H-NMR spectrum (500 MHz, CD3OD) of 1 contained 6 s for tertiary Me groups at d 0.88 (Me(29)),
0.98 (Me(30)), 1.09 (Me(28)), 1.18 (Me(18)), 1.23 (Me(27)), and 1.32 (Me(26)), 2 d for secondary Me groups at
d 0.93 (J ˆ 6.8 Mz, Me(21)), 1.25 (J ˆ 6.0 Hz, Me(6'')), and 2 d for a cyclopropyl CH2 group at d 0.35 and 0.55
(each J ˆ 3.9 Hz, CH2 (19)), indicating a cycloartane skeleton in the molecule. The two anomeric-proton signals
at d 4.58 (d, J ˆ 8.5 Hz, HÀC(1')) and 5.20 (d, J ˆ 1.6 Hz, HÀC(1'')) suggested the presence of one b-d- and one
a-l-linked sugar in 1. The 13C-NMR spectrum (125 MHz, CD3OD) was compatible with a cycloartane-type
triterpene for the aglycone of 1. Of the total of 42 C-signals, 30 were attributed to the triterpenoid moiety and 12
to the saccharide part. The 13C-NMR and DEPT spectra allowed the attribution of the 30 signals to 7Me, 9 CH 2,
8 CH, and 6 quaternary C-atoms of the aglycone. Comparison of the 13C-NMR data showed good general
agreement with the previously reported saponin depressoside D [6], except for the signals in the sugar region.

Helvetica Chimica Acta Vol. 85 (2002)
691
Table 1. 13C- (125 MHz) and 1H-NMR (500 MHz) Data of Depressoside E (1) from 1D- and 2D-NMR
Experiments in CD3OD (d in ppm, J in Hz)
d(C)a)
d(H)
CH2(1)
CH2(2)
CH(3)
C(4)
CH(5)
CH2(6)
CH2(7)
CH(8)
C(9)
33.06
30.35
89.99
42.05
48.871.30 (
22.08
27.27
49.50
21.05
27.42
27.33
34.38
48.20
47.56
47.60
73.10
53.01
19.42
31.01
1.19, 1.53
1.73, 2.10
3.20 (dd, J ˆ 4.1, 10.9)
dd, J ˆ 3.0, 11.8)
0.81, 1.63
0.98, 1.28
1.62 (dd, J ˆ 3.9, 12.2)
C(10)
CH2(11)
CH2(12)
C(13)
1.13, 2.03
1.36, 1.65
C(14)
CH2(15)
CH(16)
CH(17)
Me(18)
CH2(19)
1.37, 1.95
4.51 (ddd, J ˆ 5.3, 8.0, 8.2)
1.96 (dd, J ˆ 6.8, 11.9)
1.18 (s)
0.35 (d, J ˆ 3.9)
0.55 (d, J ˆ 3.9)
2.28 (m)
0.93 (d, J ˆ 6.8)
4.02 (ddd, J ˆ 3.0, 7.2, 8.3)
1.78 (m)
CH(20)
Me(21)
CH(22)
CH2(23)
33.38
16.02
81.12
36.24
2.21 (m)
CH(24)
C(25)
78.35
84.21
26.01
23.15
26.171.09 (
15.50
20.54
104.0
73.8
77.00
78.64
77.40
61.80
4.03 (dd, J ˆ 4.0, 6.9)
Me(26)
Me(27)
Me(28)
Me(29)
Me(30)
Glc: CH(1')
CH(2')
CH(3')
CH(4')
CH(5')
CH2(6')
1.32 (s)
1.23 (s)
s)
0.88 (s)
0.98 (s)
4.58 (d, J ˆ 8.5)
3.08 (m)
3.45 (m)
4.51 (m)
3.37 (m)
3.69 (dd, J ˆ 5.2, 10.7)
3.85 (dd, J ˆ 2.8, 10.7)
5.20 (d, J ˆ 1.68)
3.51 (m)
3.43 (m)
3.11 (m)
Rha: CH(1'')
CH(2'')
CH(3'')
CH(4'')
CH(5'')
102.3
71.80
72.20
73.70
68.80
18.10
3.01 (m)
1.25 (d, J ˆ 6.0)
Me(6'')
a) Attached protons by DEPT.

692
Helvetica Chimica Acta Vol. 85 (2002)
The presence of 3 downfield CH signals at d 89.99, 73.10, and 78.35 and a far-downfield quaternary C-atom at
d 84.21 confirmed that the aglycone in 1 is the previously described genin depressogenin [5]. The presence of an
additional Me group in 1 was attributed to the rhamnopyranosyl unit. The 13C-NMR spectrum contained 2
anomeric C-signals at d 102.3 and 104.0. The sugar moieties were identified as a-l-rhamnopyranose and b-d-
glucopyranose. The 13C-NMR glycosidation shift for C(3) and the HMBC signals observed between HÀC(1')
(d 4.58) of the glucose unit and C(3) (d 89.99) of the aglycone confirmed that the oligosaccharide moiety is
attached at C(3) of the aglycone. The anomeric proton of the rhamnose moiety at d 5.20 (HÀC(1'')) exhibited
long-range correlations with C(4') of the glucose moiety at d 78.64. A strong inter-residual NOE between the
anomeric proton of the rhamnose (d 5.20) and HÀC(4') of the glucose (d 4.51) unit was clearly observed, which
further supported a 1 ! 4 linkage between the rhamnose and glucose units [7].
Depressoside F (2) was isolated as white solid. The positive-ion FAB-MS of 2
‡
‡
exhibited a quasi-molecular-ion peak at m/z 821 ([M ‡ Na] , [C42H71O14 ‡ Na] ). The
fragment ions at m/z 659 and 497and the negative-ion FAB-MS indicated the presence
of two hexose units in the molecule. The enzymatic hydrolysis of saponin 2 with the
enzyme a-glucosidase gave the previously reported glycoside depressoside A (3) [5],
1
establishing that the terminal sugar in 2 is a-d-glucose. In accord with the H- and
13C-NMR data (Table 2), depressoside F (2) was identified as (22R,24S)-22,25-epoxy-
9,19-cyclolanostane-3b,16b,24-triol 3-[a-d-glucopyranosyl-(1 ! 3)-b-d-glucopyranoside].
The 1H-NMR spectrum (500 MHz, CD3OD) of 2, in addition to other signals, showed two anomeric signals
at d 4.32 (d, J ˆ 3.5 Hz) and 4.58 (d, J ˆ 8.0 Hz) also suggesting the presence of one a-d- and one b-d-linked
sugar in the molecule. In the 13C-NMR spectrum (CD3OD, 125 MHz), the anomeric C-atoms were observed at
d 100.2 and 103.5. It has been reported earlier that the anomeric C-atom of methyl a-d-glucopyranoside appears
at d 100.0 and of methyl b-d-glucopyranoside at d 103.9 [8]. As the anomeric proton corresponding to d(C)
100.2 of 2 showed a small coupling constant (3.5 Hz), the presence of one a-d-glucose unit was confirmed. The
position of the sugar residues was unambiguously assigned by comparison of the 13C-NMR data with that of the
aglycone, depressogenin, and was further confirmed by a HMBC experiment. The cross peak due to long-range
correlations between C(3) (d 90.01) of the aglycone and HÀC(1') of b-Glc (d 4.58) confirmed that the glucose
residue was linked to C(3) of the aglycone. The cross peaks between C(3') of b-Glc (d 83.9) and HÀC(1'') of a-
Glc (d 4.32) confirmed the location of the second glucose unit at C(3') of b-Glc.
The flavonol glycosides 4 and 5 were obtained as dark yellow amorphous powders,
which appeared violet on TLC under UV light (366 nm) and turned yellow with NH3.
Acid hydrolysis of 4 and 5 with 2n HCl yielded kaempferol (ˆ 3,5,7-trihydroxy-2-(4-
hydroxyphenyl)-4H-1-benzopyran-4-one) (co-elution with standard on TLC (co-
TLC), UV, EI-MS, and 1H-NMR), glucose, galactose, and arabinose. The sugars were
identified by co-TLC and also by GC analysis after trimethylsilylation [9]. The
conclusions drawn from FAB-MS, 1H-NMR, NOE difference measurement, and
13C-NMR of 4 were also confirmed by 1H,1H COSY, HMQC, and HMBC experiments
(see Table 3) and by comparison with published data (see below). Therefore,
compound 4 is identified as kaempferol 3-[b-d-glucopyranosyl-(1 ! 4)-b-d-galactopyr-
anoside] 7-(a-l-arabinofuranoside).
On the basis of spectroscopic data (Table 3) and comparison with 4, the structure of
compound 5 is established as kaempferol 3-[b-d-glucopyranosyl-(1 ! 6)-b-d-galacto-
pyranoside] 7-(a-l-arabinofuranoside).
The UV spectrum of 4 in MeOH had absortion maxima at 263 and 347nm, which is typical for a flavonol
glycoside [10]. The bathochromic shift (47nm) of band-I in AlCl 3/HCl solution/MeOH and the absence of a
shift on band-II in NaOAc/MeOH solution suggested that 4 is a 3,7-disubstituted flavonol glycoside [11][12].
The EI-MS of 4 showed a base peak at m/z 286 along with other diagnostic fragments, which confirmed

Helvetica Chimica Acta Vol. 85 (2002)
693
Table 2. 13C- (125 MHz) and 1H-NMR (500 MHz) Data of Depressoside F (2) from 1Dand 2D-NMR
Experiments in CD3OD (d in ppm, J in Hz)
d(C)a)
d(H)
CH2(1)
CH2(2)
CH(3)
C(4)
CH(5)
CH2(6)
CH2(7)
CH(8)
C(9)
33.08
30.30
90.01
42.15
49.0
22.12
27.55
49.79
21.10
27.32
27.23
34.40
48.54
47.59
47.91
73.0
1.20, 1.55
1.72, 2.13
3.22 (dd, J ˆ 4.0, 10.5)
1.35 (dd, J ˆ 3.4, 11.7)
0.80, 1.64
0.97, 1.29
1.60 (dd, J ˆ 3.8, 12.0)
C(10)
CH2(11)
CH2(12)
C(13)
1.15, 2.01
1.30, 1.63
C(14)
CH2(15)
CH(16)
CH(17)
Me(18)
CH2(19)
1.38, 1.92
4.55 (ddd, J ˆ 5.4, 8.1, 8.5)
1.98 (dd, J ˆ 7.0, 12.1)
1.18 (s)
0.37( d, J ˆ 4.2)
0.58 (d, J ˆ 4.2)
2.25 (m)
0.95 (d, J ˆ 6.9)
4.00 (ddd, J ˆ 2.9, 7.1, 8.0)
m)
52.72
19.22
29.89
CH(20)
Me(21)
CH(22)
CH2(23)
33.35
16.05
81.12
36.271.7
(
7
2.20 (m)
CH(24)
C(25)
78.49
84.18
26.05
23.32
26.29
15.45
20.62
103.5
73.8
83.9
68.9
77.4
61.8
4.02 (dd, J ˆ 4.1, 7.1)
Me(26)
Me(27)
Me(28)
Me(29)
Me(30)
b-Glc: CH(1')
CH(2')
CH(3')
CH(4')
CH(5')
CH2(6')
1.33 (s)
1.25 (s)
1.10 (s)
0.89 (s)
0.96 (s)
4.58 (d, J ˆ 8.0)
3.06 (m)
4.02 (m)
3.26 (m)
3.19 (m)
3.72 (m)
3.40 (m)
4.32 (d, J ˆ 3.5)
3.09 (m)
3.14 (m)
3.09 (m)
3.15 (m)
3.65, 3.45 (2m)
aGlc: CH(1'')
CH(2'')
CH(3'')
CH(4'')
CH(5'')
100.2
72.3
75.9
70.2
76.5
60.8
CH2(6'')
a) Attached protons by DEPT.

694
Helvetica Chimica Acta Vol. 85 (2002)
Table 3. 13C-Data (125 MHz) of Depressonols A (4) and B (5) from 1Dand 2D-NMR Experiments in CD 3OD
(d in ppm)
d(C)a) of 4
d(C)a) of 5
C(2)
C(3)
C(4)
C(5)
158.3
135.5
178.9
163.9
99.8
158.1
135.2
180.1
162.8
99.9
CH(6)
C(7)
CH(8)
163.8
95.9
163.1
95.5
C(9)
C(10)
C(1')
CH(2')
CH(3')
C(4')
158.5
104.2
121.5
132.5
117.5
160.2
117.5
132.5
101.1
71.4
73.9
75.6
77.4
62.5
103.4
74.3
76.5
69.769.5
76.7
61.9
158.3
103.5
122.1
132.3
116.9
159.5
116.9
132.3
99.9
71.3
74.3
69.8
77.5
CH(5')
CH(6')
Gal: CH(1'')
CH(2'')
CH(3'')
CH(4'')
CH(5'')
CH2(6'')
Glc: CH(1''')
CH(2''')
CH(3''')
CH(4''')
CH(5''')
CH2(6''')
Ara: CH(1'''')
CH(2'''')
CH(3'''')
CH(4'''')
CH2(5'''')
67.2
103.5
74.2
76.0
76.4
62.8
108.9
81.5
77.6
87.5
62.5
108.4
81.4
77.3
85.2
61.1
a) Attached protons by DEPT.
kaempferol as the aglycone. The positive-ion FAB-MS of 4 displayed a quasi-molecular-ion peak at m/z 765
‡
‡
([M ‡ Na] , [C32H38O20 ‡ Na] ). In addition, two fragment-ion peaks were observed at m/z 471 ([M ‡ Na À
‡
‡
132 À 162] ) and 309 ([M ‡ Na À 132 À 2  162] ), indicating the attachment of either two interlinked hexoses
at position C(3) and a pentose at C(7) or of one hexose interlinked to a pentose at position C(3) and a hexose at
1
position C(7) of the aglycone or vice versa. In the H-NMR spectrum of 4, three one-proton d at d 5.54 (J ˆ
6.9 Hz), 5.30 (J ˆ 7.2 Hz), and 5.68 (J ˆ 1.0 Hz), typical for b-d- and a-l-sugar configurations, were assigned to
the anomeric protons of a galactose, glucose, and arabinose moiety, respectively. The remaining sugar protons
resonated at d 3.30 4.58 ppm. In the NOE experiments, irradiation of HÀC(8) of the aglycone enhanced the
anomeric-proton signal of arabinose, indicating its attachment at C(7). Similarly, irradiation of HÀC(2') and
HÀC(6') produced an NOE at the anomeric protons of galactose, indicating its attachment at C(3) of the
aglycone. A strong inter-residual NOE connecting the anomeric proton of glucose to HÀC(4'') of galactose at
d 3.68 was clearly detected, which supported a 1 ! 4 type linkage [7]. The 13C-NMR chemical shifts of
compound 4 were similar to those reported for kaempferol 3-(sophorside) 7-(a-l-arabinofuranoside) [13],
except for the signals arising from the sugars at position C(3), which were consistent with those already
published for lilyn (kaempferol 3-(glucosyl galactoside)) [14]. The a-d-anomeric linkage between the
arabinofuranose and the flavone is supported by the small coupling constant (ca. 1.0 Hz) of the anomeric proton

Helvetica Chimica Acta Vol. 85 (2002)
695
of this sugar moiety [13]. The anomeric C-atoms of the galactose, glucose, and arabinose units of 4 appeared at
d 101.1, 103.4, and 108.4, respectively. A comparison of the 13C-NMR sugar signals with the reported values for
lilyn indicated a 5.8-ppm downfield shift for C(4'') of the galactose [14]. This downfield shift of C(4'') established
the 1 ! 4 linkage between the glucose and galactose units and confirmed the results obtained by NOE
experiments. The 13C-NMR signals additional to those of a kaempferol 3-(glucosylgalactoside) were observed at
d 108.7, 82.6, 78.5, 86.4, and 63.0 and were consistent with published data for an arabinofuranoside rather than an
arabinopyranoside moiety [15 17].
The UV and EI- and FAB-MS data of compound 5 were similar to those of compound 4. In the 1H-NMR
spectrum of 5, the ds for three anomeric protons were observed at d 5.28 (J ˆ 7.2 Hz), 5.59 (J ˆ 6.9 Hz), and 5.62
(J ˆ 1.3 Hz). The 13C-NMR, NOE difference measurements, and 2D NMR experiments showed that the only
difference between compounds 4 and 5 is the 1 ! 6 interglycosidic linkage between the glucose, and galactose
units, which was also confirmed by a downfield shift (6.5 ppm) of C(6'') of the galactose unit. Anomeric C-atom
signals of the galactose, glucose, and arabinose units appeared at d 99.9, 103.5, and 108.9, respectively.
All new and known depressosides are currently being tested for different enzyme-
inhibition activities. Depressoside A (3) has shown inhibitory activity against a-
glucosidase enzyme type-VI (Sigma, No G6136) with an IC50 of 0.236 mm.
Experimental Part
General. VLC (CHCl3/MeOH): silica gel 60 (35 70 mesh, Merck). Column chromatography (CC):
Sephadex LH-20 (Pharmacia). Flash chromatography (FC): Eyela EF-10 flash-chromatography instrument;
column packed with RP-8 silica (Merck, No 16105). HPLC: Shimadzu LC-6A dual-pump system with RID-6A
and SPD-6A UV detectors; RP-18 reversed-phase semi-prep. column. TLC: pre-coated silica gel 60, F 254
aluminum sheets (Merck). GC: sugar analysis was carried out by GC of trimethylsilyl derivatives on SE-54
(25 Â 0.25 mm) at a flow rate of 4.0 ml minÀ1 with N2 as carrier gas. Optical rotations: Jasco DIP-360 instrument.
M.p.: uncorr.; Gallenkamp melting-point apparatus. UV: in nm. IR: Jasco A-320 spectrophotometer; in cmÀ1
.
1H- and 13C-NMR (125 MHz): at 500 and 125 MHz, resp.; Bruker AM-500 spectrometer; chemical shifts d in
ppm, coupling constants J in Hz; 2D-NMR experiments included H,1H COSY, HMQC, NOESY, DEPT, and
1
HMBC. EI-MS: Finnigan MAT-312 double-focusing mass spectrometer. FAB-MS: Jeol JMS-HX-110
spectrometer; in m/z (rel. int. %).
Plant Material. The plant material was collected in Karachi in August 2000. A voucher specimen of the
plant is deposited at the herbarium of the Department of Botany, University of Karachi (voucher specimen
#2300).
Extraction and Isolation Procedures. Air-dried whole plants of Corchorus depressus (10 kg) were extracted
with EtOH (7days Â3). The EtOH extract was evaporated and the gummy residue (200 g) partitioned between
hexane, AcOEt, and BuOH. The BuOH extract was evaporated and the solid residue (25 g) then subjected to
VLC (gradient CHCl3/MeOH). The VLC fraction eluted with CHCl3/MeOH 75 :25 gave a mixture of crude
saponins that was subjected to CC (Sephadex LH-20, MeOH/H2O 1 :1). The fractions obtained were subjected
to reversed-phase FC (Lichrosphere RP-8 silica gel (20 g). The fractions eluted with MeOH/H2O 60 :40
revealed the presence of two partially overlapping spots on TLC (BuOH/AcOH/H2O 12 :3 :5). These FC
fractions were submitted to HPLC (semi-prep. RP-18 (24.4 cm  40 mm), isocratic MeOH/H2O 70 :30, flow rate
1 ml/min, refractive-index detector): 1 (15.7mg; tR 11.7min) and 2 (12.3 mg; tR 15.3 min).
The VLC fractions eluted with CHCl3/MeOH 70 :30 to 65 :35 showed the presence of partially overlapping
yellow spots on TLC (BuOH/AcOH/H2O 12 :3 :5) along with impurities. These combined fractions were
subjected to CC (Sephadex LH-20, MeOH/H2O 60 :40). The fractions obtained containing partially overlapped
yellow spots free of impurities were purified by HPLC (semi-prep. RP-18 (24.4 cm  40 mm), isocratic MeOH/
H2O 60 :40), flow rate 1.5 ml/min, UV detector): 4 (11.6 mg; tR 7.5 min) and5 (9.8 mg; tR 9.4 min). The purity of
1, 2, 4, and 5 was again checked on HP-TLC plates, and spots were visualized by spraying with ceric ammonium
sulfate reagent followed by heating.
Depressoside E (ˆ(3b,16b,22R,24S)-22,25-Epoxy-3-{[4-O-(a-l-rhamnopyranosyl)-b-d-glucopyranosyl]-
oxy}-1,19-cyclolanostane-16,24-diol ˆ (3b,16b,22R,24S)-22,25-Epoxy-16,24-dihydroxy-1,19-cyclolanostan-3-yl
4-O-(a-l-Rhamnopyranosyl)-b-d-glucopyranoside; 1). Amorphous solid. M.p. 212 2148. [a]2D5 ˆ À19.8 (c ˆ
1
‡
‡
0.18, MeOH). H- and 13C-NMR (CD3OD): Table 1. FAB-MS (pos.): 805 ([M ‡ Na] ), 783 ([M ‡ H] ), 659

696
Helvetica Chimica Acta Vol. 85 (2002)
‡
([M ‡ Na À 146]‡), 641 ([M ‡ Na À 146 À H2O]‡), 497([ M ‡ Na À 146 À 162]‡), 461 ([M ‡ Na À 146 À 162 À H2O] ).
‡
H2O] ). FAB-MS (neg.): 781 ([M À H]À), 635 ([M À H À 146]À), 473 ([M À H À 146 À 162]À), 455 ([M À
H À 146 À 162 À H2O]À).
Depressoside F (ˆ(3b,16b,22R,24S)-22,25-Epoxy-3-{[3-O-(a-d-glucopyranosyl)-b-d-glucopyranosyl]oxy}-
1,19-cyclolanostane-16,24-diol ˆ (3b,16b,22R,24S)-22,25-Epoxy-16,24-dihydroxy-1,19-cyclolanostan-3-yl 3-O-
(a-d-Glucopyranosyl)-b-d-glucopyranoside; 2) Amorphous solid. M.p. 202 2048 (dec.). [a]2D5 ˆ À10.9 (c ˆ
1
‡
‡
0.24, MeOH). H- and 13C-NMR (CD3OD): Table 2. FAB-MS (pos.): 821 ([M ‡ Na] ), 799 ([M ‡ H] ), 659
‡
‡
‡
([M ‡ Na À 162] ), 641 ([M ‡ Na À 162 À H2O] ), 497([ M ‡ Na À 2  162] ), 479 ([M ‡ Na À 2  162 À
H2O] ). FAB-MS (neg.): 797 ([M À H]À), 635 ([M À H À 162]À), 599 ([M À H À 162 À 2 H2O]À), 473 ([M À
‡
H À 2 Â 162]À), 455 ([M À H À 2 Â 162 À H2O]À).
Enzymatic Hydrolysis of 2. Saponin 2 (0.2 mm), mixed with sodium phosphate (50 mm) and sodium
chloride (100 mm) (pH 6.8), was incubated with the enzyme a-glucosidase (from Brewers yeast; 0.032 U/ml,
Sigma No. 6136) for 1 h at 378, and the product was extracted with MeOH. The hydrolyzed product was
identified as depressoside A (ˆ(22R,24S)-22,25-epoxy-9,19-cyclolanostane-3b,16b,24-triol 3-b-d-
glucopyranoside] ˆ (3b,16b,22R,24S)-22,25-epoxy-16,24-dihydroxy-1,19-cyclolanostan-3-yl b-d-glucopyrano-
side), by comparing its NMR data with the literature values [5], thus confirming that the second sugar unit
of 2 has an a-d-glucosidic linkage.
Depressonol A (ˆ 7-[(a-l-Arabinofuranosyl)oxy]-3-{[4-O-(b-d-glucopyranosyl)-b-d-glucopyranosyl]-
oxy}-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one; 4). Yellow amorphous powder. UV (MeOH): 261, 346.
UV (MeOH ‡ NaOMe): 266, 380. UV (MeOH ‡ AlCl3/HCl soln.): 270, 300, 345, 393. UV (MeOH ‡ NaOAc/
1
H3BO3): 266, 350. H-NMR (CD3OD, 500 MHz): 5.30 (d, J ˆ 7.2, HÀC(1) of Glc); 5.54 (d, J ˆ 6.9, HÀC(1) of
Gal); 5.68 (d, J ˆ 1.0, HÀC(1) of Ara); 6.43 (d, J ˆ 2.2, HÀC(6)); 6.70 (d, J ˆ 2.2, HÀC(8)); 6.88 (d, J ˆ 8.8 Hz,
HÀC(3'), HÀC(5')); 7.99 (d, J ˆ 8.8, HÀC(2'), and HÀC(6')). 13C-NMR (CD3OD): Table 3. EI-MS: 286 (100),
‡
285 (17.0), 258 (8.1), 153 (5.8), 121 (30.5), 93 (10.8). FAB-MS (pos.): 765 ([M ‡ Na] ), 471 ([M ‡ Na À 132 À
‡
‡
162] ), 309 ([M ‡ Na À 132 À 2  162] ).
Depressonol B (5). Yellow amorphous powder. UV (MeOH): 266, 347. UV (MeOH‡ NaOMe): 266, 386.
UV (MeOH ‡ AlCl3): 262, 299, 346, 394. UV (MeOH ‡ AlCl3/HCl): 270, 274, 300, 393. UV (MeOH ‡ NaOAc/
1
H3BO3): 266, 348. H-NMR (CD3OD, 500 MHz): 5.28 (d, J ˆ 7.2, HÀC(1) of Glc); 5.59 (d, J ˆ 6.9, HÀC(1) of
Gal); 5.62 (d, J ˆ 1.3, HÀC(1) of Ara); 6.42 (d, J ˆ 2.0, HÀC(6)); 6.73 (d, J ˆ 2.0, HÀC(8)); 6.89 (d, J ˆ 8.1,
HÀC(3'), HÀC(5')); 8.05 (d, J ˆ 8.1, HÀC(2'), HÀC(6')). 13C-NMR (CD3OD): Table 3. EI-MS: 286 (100), 285
‡
(17.0), 258 (8.1), 153 (5.8), 121 (30.5), 93 (10.8). FAB-MS (pos.): 765 ([M ‡ Na] ), 471 ([M ‡ Na À 132 À
‡
‡
162] ), 309 ([M ‡ Na À 132 À 2  162] ).
Acid Hydrolysis of Depressonol A (4) and B (5). Each flavonol glycoside (6.0 mg) in 2n HCl (5 ml) was
refluxed for 1 h. The aglycones were extracted with AcOEt and identified by co-TLC with an authentic sample
of kaempferol, UV, and 1H-NMR spectra. The sugars were isolated from the aq. layer in the usual way and
identified by co-TLC (cellulose, BAW, BEW, EPAW, and BBPW) with authentic samples and by GC analysis of
their Me3Si derivatives [9].
M. Z. gratefully acknowledges the postdoctoral fellowship awarded by the Zhejiang University, Hangzhou,
P.R. China.
REFERENCES
[1] S. I. Ali, E. Nasir, −Flora of Pakistan×, No. 75, Ferozsons, Karachi, Pakistan, 1974, p. 20.
[2] L. Perry, J. Metzger, −Medicinal Plants of East and Southeast Asia×, MIT Press, Cambridge, England, 1980,
p. 407.
[3] M. L. Harsh, T. N. Nag, Geobios 1988, 15, 32.
[4] M. S. Y. Khan, K. Javed, M. H. Khan, M. A. Shamsi, A. A. Siddiqui, Phytochemistry 1991, 30, 1989.
[5] V. U. Ahmad, A. Ali, Z. Ali, F. T. Baqai, F. N. Zafar, Phytochemistry 1998, 49, 829.
[6] V. U. Ahmad, A. Ali, Z. Ali, F. N. Zafar, M. Zahid, Chem. Pharm. Bull. 2000, 49, 829.
[7] S. Homas, Prog. NMR Spectrosc. 1990, 22, 55.
[8] P. E. Pfeffer, K. M. Valentine, F. W. Parish, J. Am. Chem. Soc. 1979, 101, 1265.
[9] K. R. Markham, −Techniques of Flavonoid Identification×, Academic Press, London, 1982.
[10] T. J. Mabry, K. R. Markham, M. B. Thomas, −The Systematic Identification of Flavanoids×, Springer, Berlin,
1970.

Helvetica Chimica Acta Vol. 85 (2002)
[11] M. Veit, G. F. Pauli, J. Nat. Prod. 1999, 62, 1301.
697
[12] A. Hasan, I. Ahmad, M. A. Khan, M. I. Choudhary, Phytochemistry 1996, 43, 1115.
[13] A. K. R. Markham, O. M. Anderson, Phytochemistry 1990, 29, 3919.
[14] E. Nagy, I. Seres, G. Verzar-Petri, Z. Naturforsch., B 1984, 39, 1813.
[15] K. R. Markham, V. M. Chari, in −The Flavanoids: Advances in Research, 1975 1981×, Eds. J. B. Harbone
and T. J. Mabry, Chapman and Hall, London, 1982, p. 19.
[16] P. K. Agarwal, D. C. Jain, R. K. Gupta, R. S. Thakur, Phytochemistry 1985, 24, 2479.
[17] K. Yasukawa, H. Ogawa, M. Takido, Phytochemistry 1990,29, 1707.
Received September 12, 2001