Estrogenic activity as a function of chemical structure in Haplophyllum quinoline alkaloids

Article abstract of DOI:10.1023/A:1014873000974

The estrogenic activity of 15 quinoline alkaloids isolated from plants of the Haplophyllum genus and two derivatives was studied. These compounds exhibit estrogenic activity that depends on the type of heterocyclic skeleton, N atom basicity, and substituent.

Full text of DOI:10.1023/A:1014873000974

Chemistry of Natural Compounds, Vol. 37, No. 6, 2001
ESTROGENIC ACTIVITY AS A FUNCTION OF CHEMICAL
STRUCTURE IN Haplophyllum QUINOLINE ALKALOIDS
S. S. Nazrullaev, I. A. Bessonova,
and Kh. S. Akhmedkhodzhaeva
UDC 547.944/945+615.217
The estrogenic activity of 15 quinoline alkaloids isolated from plants of the Haplophyllum genus and two
derivatives was studied. These compounds exhibit estrogenic activity that depends on the type of heterocyclic
skeleton, N atom basicity, and substituent.
Key words: Haplophyllum, Rutaceae, quinoline alkaloids, estrogenic activity.
Plants of the Haplophyllum A. Juss. (Rutaceae) genus have long been known for their medicinal properties [1]. The
extracts of certain plants are widely used in folk medicine as analgesics, antispamodics, diuretics, and sedatives and as topical
agents for skin diseases, etc. [2-4]. Ruta is also known to affect reproductive organs, induce abortion, and act as a contraceptive
[5].
One third of the more than 200 quinoline alkaloids isolated from Rutaceae plants occur in the Haplophyllum genus,
being a unique source of various quinoline alkaloids [6, 7].
OCH
OCH3
OCH
OCH
3
3
3
R
N
O
N
O
OR
OH
HO
H C
N
O
O
N
O
OCH
2
OCH
OCH
3
3
3
R
1
- 6
7, 8
9, 10
1
1
1
2
: R = H
: R = OH
7: R = H
8: R = Ac
9: R = CH C(OH)(CH )
3 2
10: R = CH=C(CH )
3 2
2
OCH
O
C
3
3
4
: R =
O
OCH3
: R = OCH
OCH3
3
5
6
: R = O-α-L-Rhap
: R = OCH CH(OH)C(OH)(CH )
2
3 2
OCH
N
3
O
O
OH
OH
O
O
N
N
H
N
H
O
OR
CH
3
CH
3
1
2
17
1
3 - 15
16
1
1
1
3: R = H
4: R = Ac
5: R = CH CH(OH)C(OH)(CH )
2
3 2
S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan,
Tashkent, fax (99871) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 472-475, November-December,
001. Original article submitted October 22, 2001.
2
©
0
009-3130/01/3706-0551$25.00 2001 Plenum Publishing Corporation
551

Pharmacological research showed that Haplophyllum alkaloids possess a wide spectrum of pharmacological activity
with little toxicity. The majority of them have a distinct depressive effect on the CNS, exerting a sedative, soporific,
antispasmodic, and other effects. Certain alkaloids exhibit stimulant and antiarrhythmic activity and affect the uterine and
intestinal muscle tone [8-15].
The present article contains results of research on 15 quinoline alkaloids and two derivatives for estrogenic activity
in animals (estrogenic activity, effect on the menstrual cycle, and embryogenesis). This research reveals the dependence between
the chemical structure and estrogenic activity of quinoline alkaloids belonging to the furanoquinoline (1-6),
dihydrofuranoquinoline (7, 8), modified furanoquinoline (9-11), 4-hydroxyquinolin-2-one (12-15), and 2-phenyl(alkyl)-quinolin-
4
-one (16, 17) systems.
It was found that almost all these compounds possess estrogenic activity to some degree or another. Compounds 1-7,
-12, 15, and 17 exhibit this effect at a dose of 10 mg/kg (Table 1). Administration of γ-fagarine (1), glycoperine (5), perforine
9
(
9), and foliosidine (15) increased the uterine mass in immature rats by 122.1-193.9% without liquid. Certain alkaloids also
cause the uterus to hydrate. This is characteristic of estrogenic compounds. The greatest increase of uterine mass with liquid
was observed for administration of γ-fagarine (1), 283.6%.
All compounds had a dose-dependent effect. Quinoline alkaloids had the greatest estrogenic activity at doses of 50-
1
00 mg/kg (1/20-1/10 of LD ). Thus, γ-fagarine (1), a derivative of 3, glycoperine (5), evoxine (6), and acutine (17) at a dose
50
of 50 mg/kg increase the uterine mass by 251.7-403.9% without liquid and by 318.0-612.3% with liquid.
The alkaloids γ-fagarine (1) and perforine (9) a dose of 10 mg/kg reliably increased the uterine mass and also that of
ovaries by 21.5 and 29.1%. This indicates that they are gonadotropic or follicule-stimulating. A mass increase of ovaries up
to 42.5 and 26.7% was noted upon administration of 8 and 13, respectively, which exhibit weak estrogenic activity (Table 1).
The estrogenic activity of haplopine (2), its derivative 3, dubinidine (7), perfamine (11), bucharidine (12), and acutine
(
17) is significantly increased at doses of 50 and 100 mg/kg whereas these alkaloids have no effect on mass of ovaries.
These alkaloids at doses of 30, 50, and 100 mg/kg in experiments with ovariectomized rats caused proliferative changes
in the vaginal lining upon estrus in 20, 50, and 100% of the rats, respectively. The most active alkaloids were the
furanoquinolines 1, 4, and 5 and modified furanoquinolines 9 and 10.
Experiments with mature intact rats demonstrated that skimmianine, dubinidine, and perforine at doses of 50 and
100 mg/kg reliably change the menstrual cycle by lengthening the estrus phase. Thus, whereas the average duration of a single
menstruation is one day, these alkaloids extend it to 1.4, 1.3, and 1.4 days, respectively.
These alkaloids at doses of 10-20 mg/kg have essentially no effect on implantation and embryogenesis. However,
administration at a dose of 100 mg/kg, especially of skimmianine, caused an embryotoxic effect characteristic of synthetic and
natural estrogens [16-18].
Thus, Haplophyllum quinoline alkaloids were found to possess an estrogenic effect. However, compared with known
estrogens, for example, synestrol, ethynylestradiol, etc., they are effective at higher doses.
One of the principal approaches to determining the structure—activity relationship is to compare the effectiveness of
structurally similar compounds that belong to different structural categories. An analysis showed that the greatest estrogenic
effect occurs for furanoquinoline alkaloids 1-6. A common element of these is the furanoquinoline skeleton and the C-4 and
C-8 methoxyls. Adding hydroxyl, methoxyl, and 3,4,5-benzoyloxy to C-7 has little effect on the estrogenic activity whereas
furanoquinoline alkaloids with a glycosyl or hydroxylated isoprenoid substituent in this position have increased activity
(Table 1).
Th estrogenic activity sharply decreases for 7 and 8, which are dihydrofuranoquinolines. These are stronger bases than
furanoquinolines 1-6 [6]. Apparently the basicity of the N atom plays an important role in producing estrogenic activity because
the lack of a double bond in the furan ring increases the electron density on the N atom and, therefore, its basicity, i.e., the
electronic state of the N atom effects the degree of estrogenic activity. Modified furanoquinolines 10 and 11, in which the
benzene ring is partially hydrogenated (haplophylidine) or modified into a geminally substituted cyclohexadienone ring
(perfamine), except for perforine (9), exhibit weaker estrogenic activity than furanoquinolines.
It is interesting to note that the estrogenic activity of 9 is several times greater than that of 10 although they differ
chemically only by the structure of the isoprenoid substituent, which has a hydroxyl in perforine instead of the double bond in
haplophylidine. Therefore, the estrogenic activity of the alkaloids depends on the nature of the substituent.
5
52

TABLE 1. Estrogenic Activity of Quinoline Alkaloids on Immature Rats (n = 10)*
Dose,
Uterine mass gain, % of control
Mass gain of ovaries,
Compound
mg/kg
%
of control
without fluid
with fluid
γ-Fagarine (1)
Haplopine (2)
10
193.9
285.0
74.4
283.6
29.1
39.7
14.2
10.6
4.2
50
612.3
10
-
50
268.5
305.5
33.3
-
1
00
456.5
3
,4,5-Trimethoxybenzoylhaplopine (3)
10
-
-9.6
6.7
50
251.7
22.6
353.9
Skimmianine (4)
Glycoperine (5)
Evoxine (6)
10
80.8
24.9
10.4
9.5
50
97.2
158.2
10
122.1
396.0
108.3
403.9
36.4
-
50
551.2
9.9
10
-
-1.4
19.7
0.9
50
597.9
Dubinidine (7)
10
00
-
1
132.0
22.5
-
4.5
Dubinine (8)
Perforine (9)
100
10
68.2
42.5
21.5
13.7
30.1
32.5
1.2
157.6
184.3
26.8
-
1
00
350.6
Haplophylidine (10)
Perfamine (11)
10
-
50
39.3
77.0
10
45.8
-
50
87.5
121.4
2.8
Bucharidine (12)
10
48.5
-
-1.3
8.4
50
177.4
-4.3
228.5
Folifidine (13)
100
100
10
-
26.7
-35.0
10.6
7.6
Acetylfolifidine (14)
Foliosidine (15)
-15.2
176.1
204.1
18.9
25.9
-
50
257.5
1
-Methyl-2-phenylquinolin-4-one (16)
100
10
-
-
11.8
3.4
Acutine (17)
21.5
50
243.0
318.0
7.6
_
_____
*
True uterine mass gain was reliable relative to the control for all compounds except 13 and 16; gain of ovaries
was reliable for 1, 4, 5, 6, 8-10, 13, and 14.
Bucharidine (12) and foliosidine (15), which contain hydroxylated isoprenoid moieties in the 3- and 8-position,
respectively, have the highest estrogenic activity among the 4-hydroxyquinolin-2-one alkaloids 12-15. Folifidine (13) and its
acetate (14), which differ from foliosidine only by the lack of a hydroxylated isoprenoid chain on C-8, have almost no estrogenic
activity. This fact indicates also that the substituent plays a role on the degree of estrogenic activity. In particular, it indicates
that the presence of hydroxylated isoprenoids in the alkaloids of the furanoquinoline (evoxine), 5,6,7,8-
tetrahydrofuranoquinoline (perforine), and 4-hydroxyquinolin-2-one (bucharidine, foliosidine) types have significantly elevated
estrogenic activity.
With respect to 16 and 17 of the 2-phenyl(alkyl)-quinolin-4-one type, only 17 has estrogenic activity. Alkaloid 16,
which has a C-2 phenyl, exhibits a weak estrogenic effect.
553

Thus, the majority of quinoline alkaloids of Haplophyllum plants possess estrogenic activity that depends on the
heterocyclic skeleton, basicity of the N atom, and nature of the substituent.
EXPERIMENTAL
Alkaloids 1, 2, 4-7, 9-13, and 15-17 were prepared from Haplophyllum pedicellatum, H. foliosum, H. perforatum, H.
bucharicum, and H. acutifolium [7]; dubinine (8) and acetylfolifidine (14), by acetylation of dubinidine [19] and folifidine [20];
3
,4,5-trimethoxybenzoylhaplopine (3), by reaction of haplopine (2) and 3,4,5-trimethoxybenzoyl chloride in pyridine [21].
o
3
,4,5-Trimethoxbenzoylhaplopine (3), mp 203-204 C (acetone).
+
Mass spectrum (EI, 70 eV), m/z (I , %): 439 [M] (69), 244 (7), 195 (100).
rel
PMR spectrum (400 MHz, DMSO, δ, ppm, J/Hz): 3.83 (3H, s, OCH ), 3.92 (6H, s, 2×OCH ), 4.08 (3H, s, OCH ), 4.48
3
3
3
(
3H, s, OCH ), 7.26 (1H, d, J = 9, H-6), 7.40 (1H, d, J = 3, Hβ), 7.42 (2H, s, H-2 , H-6 ), 7.92 (1H, d, J = 3, Hα), 8.04 (1H, d,
3
J = 9, H-5).
The estrogenic activity of the alkaloids was determined by the Dorfman [22] and Allen—Doisy [23] methods.
Experiments were performed on immature rats of mass 35-45 g and mature ovariectomized rats of mass 170-200 g. The
indicators of an effect were uterine mass increase and appearance of estrus, respectively.
The estral cycle was determined in experiments on mature rats with a 4-5-day cycle. Females in estrus were introduced
to males (2:1) to determine the effect of the alkaloids on embryogenesis. The first day of pregnancy was considered the day on
which spermatozoids were observed. The animals were sacrificed on the 19-20th day of pregnancy. The results were treated
statistically [24].
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