Quinolizidine Alkaloids from Sophora alopecuroides
Atta-ur-Rahman,*
,²
M. Iqbal Choudhary,*
,²
Khalid Parvez,
²
Aftab Ahmed,
²
Farzana Akhtar,
²
M. Nur-e-Alam,
²
and Naeem M. Hassan
‡
International Center for Chemical Sciences, H.E.J. Research Institute of Chemistry, University of Karachi,
Karachi-75270, Pakistan, and Department of Chemistry, University of Baluchistan, Quetta, Pakistan
Received July 14, 1999
A new matrine-type alkaloid, 7R-hydroxysophoramine (1), was isolated from the aerial parts of Sophora
alopecuroides together with eight known alkaloids, 12-hydroxysophocarpine (2), sophoramine (3), 14-
hydroxymatrine, matrine, sophoridine, sophocarpine, adenocarpine, and baptifoline. The structures of
compounds 1-3 were confirmed through single-crystal X-ray diffraction analysis.
The plant Sophora alopecuroides L. (Leguminosae) is
widely distributed over a large area of the Asian continent.
1
Biological studies on the constituents found in this
plant have been performed in terms of potential sedative,
central nervous system depressant, analgesic, hypother-
mic,
2
antitussive,
3
anticancer,
4,5
nematocidal,
6
antispas-
modic,
7
antipyretic,
8
cardiotonic,
9
hypoglycemic,
l0
and many
other pharmacological activities.
11-14
In this communica-
tion, studies on S. alopecuroides have led to the isolation
of a new alkaloid (1) and several known alkaloids. Among
these alkaloids 12-hydroxysophocarpine (2), 14-hydroxy-
matrine, and adenocarpine have not been isolated previ-
ously from this species.
Results and Discussion
Aerial parts of S. alopecuroides were collected from the
Baluchistan province of Pakistan and extracted with 80%
ethanol. The extract was subjected to solvent-solvent
extraction and repeated column chromatography on Si gel
to obtain the new alkaloid, 7R-hydroxysophoramine (1)
together with seven known alkaloids: 12-hydroxysopho-
carpine
15
(2), sophoramine
16,17
(3), 14-hydroxymatrine,
18
adenocarpine,
19
matrine,
20
sophoridine,
21,22
sophocarpine
4,23
and baptifoline. The structures of the compounds were
determined unambiguously using either X-ray diffraction
technique or 1D and 2D
1
H and
13
C NMR experiments in
conjunction with the analysis of mass spectral and other
spectroscopic data.
The molecular formula of the new alkaloid 1 was
determined by HREIMS to be C
15
H
20
N
2
O
2
(m/z 260.1511).
Its IR spectrum (CHCl
3
) showed absorption bands of
hydroxyl (ν
max
3236 cm
-1
), R,-unsaturated lactam (ν
max
1540 cm
-1
for CdC and ν
max
1660 cm
-1
for CdO), and
trans-quinolizidine (ν
max
2928, 2855, 2793, and 2735 cm
-1
)
functionalities.
24
The EIMS showed a peak at m/z 243
corresponding to [M - OH]
+
. The
1
H NMR spectrum
(CDC1
3
) was very similar to that of sophoramine (3). The
downfield protons resonating at δ 7.13 (dd, J
13,14
) 8.9 Hz,
J
13,12
) 7.2 Hz), 6.40 (dd, J
12,13
) 7.2 Hz, J
12,14
) 1.2 Hz),
and 6.19 (dd, J
14,13
) 8.9 Hz, J
14,12
) 1.2 Hz) were assigned
to H-13, H-12, and H-14, respectively. Two other downfield
signals at δ 3.99 (dd, J
17,17R
) 14.2 Hz, J
17,5
) 7.0 Hz)
and 3.61 (dd, J
17R,17
) 14.2 Hz, J
17R,5
) 13.0 Hz) could be
assigned to H-17 and H-17R, respectively. The lack of any
other downfield methine signal indicated that alkaloid 1
might contain a hydroxyl group on a quaternary carbon.
The
13
C NMR spectra (BB and DEPT) of 1 showed 15
carbon signals with seven methylene, five methine, and
three quaternary carbons. The chemical shift of a quater-
nary carbon (δ 69.3) also indicated the presence of a
tertiary hydroxyl group. In the HMBC spectrum (Figure
1), the proton resonating at δ 6.19 (H-14) showed a long-
range heteronuclear connectivity with C-15 (δ 163.7), while
H-13 (δ 7.13) showed HMBC connectivities with C-15 (δ
163.7), C-14 (δ 118.1), C-12 (δ 104.1), and C-11 (δ 148.5).
H-12, resonating at δ 6.40, exhibited HMBC interactions
with C-14, C-11, and C-7 (δ 69.3), whereas H-17 (δ 3.99)
was coupled with C-15, C-11, C-6 (δ 66.5), and C-5 (δ 25.6).
These results suggested that the new alkaloid 1 is of the
matrine-type, in which a hydroxyl group is present at the
ring junction (i.e., C-7). The structure of 1 was established
unambiguously as 7R-hydroxysophoramine by X-ray dif-
fraction methods. A suitable crystal that formed in the
orthorhombic space group, P2
1
2
1
2
1
, was selected for the
experiment. Accurate lattice constants were a ) 7.836(2),
b ) 12.021(2), and c ) 14.342(8) Å, with four independent
molecules in the asymmetric unit. All unique diffraction
* Authors to whom correspondence should be addressed. Tel.: +92-21-
499-0007. Fax: +92-21-496-3373 or 496-3124. E-mail: hejric@digicom.net.pk.
²
University of Karachi.
‡
University of Baluchistan.
Figure 1. HMBC correlations in compound 1.
190 J. Nat. Prod. 2000, 63, 190-192
10.1021/np990351v CCC: $19.00 © 2000 American Chemical Society and American Society of Pharmacognosy
Published on Web 01/19/2000