Hypotensive effect of crude root extract of Solanum sisymbriifolium (Solanaceae) in normo- and hypertensive rats

:'~"

Journal of

ETHNOPHARMACOLOGY ELSEVIER

Journal of Ethnopharmacology 54 (1996) 7 12

Hypotensive effect of crude root extract of Solanum sisymbriifolium (Solanaceae) in normo- and hypertensive rats D.A.

I b a r r o l a a'*, M . H .

I b a r r o l a ~, C. V e r a % Y . M o n t a l b e t t ? ,

E.A.

Ferro b

'~Pharmacoh~Kl' ,~¢'('lioll. Research Departmen& Faculty O~ (Twmical Sciem'es, Nail(real (:nit,ersiO' 0/' ;4suncion, P.O. Bo.v 1055, Asuncion. Paragm O' hP/lJtochemirtr)" Section, Research Del)artnwH/, Fac'ullv of C/wnlica[ Science.s, Naliona] (.)*icersi(v of Asutlci(m. P.O. Bo.v 105,5. AsuncioH. Paraguay

Received 29 January 1996: revised 27 March 1996: accepted 12 April 1996

Abstract The hypotensive effect of the crude hydroalcoholic extract from root of Sohmum sisvmbri(]blium Lam. (Solanaceae) was investigated both in normotensive and hypertensive rats. The intravenous administration of the extract (50 and 100 mg/kg) produced a significant decrease in blood pressure in anaesthetized hypertensive (adrenal regeneration hypertension + deoxycorticosterone acetate (ARH + DOCA)) rats. Oral administration of the extract (10, 50, 100 and 250 mg/kg) also produced a dose-dependent hypotensive effect in conscious hypertensive animals. In anaesthetized normotensive rats, the extract (50 and 100 mg/kg, i.v.) also induced hypotension in a dose-dependent manner. Lastly, no significant effect on blood pressure was produced by the extract when administered orally (10, 50, 100, 250. 500 and 1000 mg/kg) to conscious normotensive rats. Keywords: Sohmum sisymbriiJolium Lain.: Antihypertensive agents: ARH + DOCA (adrenal regeneration hyper-

tension + deoxycorticosterone acetate)

1. Introduction The worldwide increasing d e m a n d for medicine from natural sources (Lapa, 1992) has motivated us to search for plants with potential hypotensive activity. The root o f S o k m u m sisvmbri(fidium

* Corresponding author.

Lam. (Solanaceae), a perennial herb found in eastern Paraguay, is claimed to possess diuretic and antihypertensive properties, and it is used in P a r a g u a y a n traditional medicine (Gonzales Torfez, 1992). The root o f this plant has also been reported as an emenagogue (Martinez-Crovetto, 1981) and fertility regulator (Hnatyszyn et al., 1974). Intoxication o f horses by the plant has been reported in Argentina, and a hemolytic gly-

0378-8741/96/$15.00 < 1996 Elsevier Science Ireland Ltd. All rights reserved PI1 S0378-8741 (96)(I1442-0

8

D.A. lbarrola el al. / Journal
coside from the fruit has also been found (Burkart, 1978). Several alkaloids have been isolated from the root, such as cuscohygrine (Evans and Somanabandhu, 1980), solacaproine (Maldoni, 1984), solamine, solasodiene and solasodine (Mazumdar. 1984). However, we have found no scientific references on any experimental evaluation of the hypotensive properties which traditional medicine ascribes to this plant. Hypertension is a significant health problem because of the percentage of the population affected and the serious consequences of uncontrolled high blood pressure. In general terms, hypertension continues to be a major risk factor for stroke, congestive heart failure, and coronary artery disease (Gerber and Nies, 1990). Adrenal regeneration hypertension + deoxycorticosterone acetate (ARH + DOCA) is a form of experimental hypertension in the rat which may be a counterpart of some forms of human low renin essential hypertension (Gomez-Sanchez et al., 1977). In the present paper, we report on the hypotensive effects of S. sisymbri~blium Lain., both on normo- and hypertensive rats (anaesthetized and conscious animals).

2. Materials and methods

2.1. Preparation oJ' extract Samples of S. sisymbri(folium Lain. were collected from the eastern region of Paraguay in February 1991 and were identified at the herbarium of the Faculty of Chemical Sciences, where a voucher herbarium specimen has been deposited (Sofia 5.248). Fresh root samples (3 kg) were air-dried and ground, yielding 1.335 kg of powder. The powder was extracted with a mixture of ethanol:water (70:30) by a conventional reflux method for 1 h. The total volume of the mixture was 19.0 1. The extraction was repeated 3 times and the filtered hydro-ethanolic extract was mixed and evaporated under reduced pressure. The concentrated extract was frozen and finally freeze-dried to yield 126 g of powder. Thus, 1 mg of lyophilized extract was obtained from 10.6 g of dry root powder.

2.2. Animals Albino normotensive rats (Wistar strain) of either sex, weighing 180-300 g, were used for the studies of effect on blood pressure, while young Wistar rats of either sex, weighing 70--80 g, were used to induce experimental hypertension. A 12 h dark-light cycle, 23-25°C temperature and 50% 60% humidity, was maintained inside the animal room. The animals received standard food and, prior to experimentation, were fasted overnight with access to water ad libitum.

2.3. Drugs Heparin, atropine, acetylcholine, norepinephrine and deoxycorticosterone acetate (DOCA) were obtained from Sigma Chemical Company (St. Louis, MO, USA), pentobarbital (Nembutal) from Abbott (Japan), and propyleneglycol for pharmaceutical use was purchased locally.

2.4. Induction of experimental hypertension (ARH + DOCA ) Forty Wistar rats (80-100 g) of either sex were anesthetized with pentobarbital (35 mg/kg, i.p.). Unilateral nephrectomy and bilateral adrenal enucleation were performed, using a retroperitoneal approach through a flank incision, as described by Stanton (1975). Briefly, the medullary tissue, both right and left, was removed by incising the capsule and gently extruding the glandular tissue with forceps. After surgery, all animals were placed in individual cages with free access to food and 1% NaCI solution as drinking water. Both in the first and second week following recovery, all animals received DOCA (15 rag/animal, s.c.). The indirect blood pressure was determined weekly using the manometer unit KN-210-3 (Natsume-Japan).

2.5. Intact preparation of normo- and hypertensive rats Wistar rats of either sex (150-300 g) were anesthetized with pentobarbital (35 mg/kg, i.p.). Surgery and cannulations were performed as de-

D.A. Ibarroh~ el a/. Journal of EtlmoplmrmacoloKv 54 (1996) 7 12

;

9

-]2C0

mmOg . . . . . . .

..10

O0 [BP ?0 mmHg ) Fig. 1. Representative tracing on arterial blood pressure (BP) of S. sisymbri!'lolium Lain. extract in anesthetized normotensive rats (0.1. 1.0, 10.0, 50.0 and 100.0 mg/kg, i,v.); n = 4 for each dose.

scribed by the Staff of the Department of Pharmacology, University of Edinburgh (1970). The blood pressure from the carotid artery was recorded using a Gould Statham P23 ID transducer connected to a blood pressure amplifier unit (Model 1257, Nec-San Ei Instruments, Ltd.). The femoral vein was cannulated for drug administration. Electrocardiograms (ECG) were recorded using a bioelectric amplifier unit (Model 1253A, Nec-San Ei Instruments, Ltd.) by inserting needle electrodes into the muscle. Heart rate was measured with a tachometer (Model 1321, Nec-San Ei Instruments, Ltd.) connected to the output of the ECG bioelectric amplifier. The trachea was cannulated and the breathing rate and exhaled breath were measured using a CO2 monitor (Respina 1H31, Nec-San Ei Instruments, Ltd.). All the signals were registered by a heat sensitive recording system (Rectigraph 8K, Nec-San Ei Instruments, Ltd.). 2.6. Intact preparation of conscious normo- and hypertensive rats After a training period, both the normotensive and hypertensive groups of rats were sub-

jected to oral administration of different doses of the extract (10, 50, 100, 250, 500 and 1000 mg/kg). In all cases, the animals were warmed individually at 60°C for 1 min in a pre-heat box in order to dilate small arteries so as to allow a better detection of blood flow through the tail. Three animals were used for each dose and the blood pressure was determined before and alter extract administration with 1 h intervals, during 5 h. The control group received a proportionate volume of vehicle (1% propylenglycol). Results are expressed as mean _+ S.D, and the statistical analysis of the data was performed by the Student's t-test.

3. Results

3.1. Effect of S. sisvmbriifolium Lain extract on anaesthetized normotensive and hypertensive rats A clear hypotensive effect was observed on anaesthetized normotensive rats at doses of 50 and 100 mg/kg, i.v., in a dose-dependent manner (Fig. 1). Doses below 50 mg/kg did not provoke a significant effect on the blood pressure. In anaesthetized hypertensive rats, the

10

D.A. lbarro/a et al. ,; Journal o~ Etlmopharmacology 54 (1996) 7 12

20O BP 100 , I'nl'n~

io - 200 BP - 100

mrr~ -0

BP

m~ -J0 Fig. 2. Representauve tracing on arterial blood pressure (BP) of S. si.~Tmbriifi,lium Lam. extract in anesthetized experimentally hypertensive rats (0.1, 1.0, 10.0, 50.0 and 100.0 mg,kg, i.v.): n =4 for each dose. administration of 50 and 100 nag of extract/kg, i.v., produced a significant decrease in blood pressure, and the effect was particularly strong at a dose of 100 mg/kg (Fig. 2). Both the systolic and diastolic blood pressure appeared to be affected proportionately (Fig. 3a,b).

3.2. EJJect o/' the extract on conscious normotensive and hypertens'ive rats. No significant effect on blood pressure was produced by the extract when administered to conscious normotensive rats at doses of 10, 50, 100, 250, 500 and 1000 mg/kg, p.o. When conscious hypertensive rats were used, the administration of 10, 50, 100 and 250 mg/kg, p.o., produced a remarkable hypotension in a dosedependent fashion (Fig. 4a,b). At doses of 500 and 1000 mg/kg, p.o., the blood pressure decrease did not follow the same rate of dose dependency observed at lower doses. This may be due to absorption difficulties.

4. D i s c u s s i o n and c o n c l u s i o n s

The present study shows the hypotensive effect produced by the crude hydro-alcoholic root extract of S. sisymbriiJblium Lam. when administered to experimentally induced hypertensive rats by the oral route. This hypotensive effect lasted from 3.5 to 4.5 h and the animal did not show any toxic reaction. When this test was performed orally in normotensive rats, no hypotensive effect was detected; rather, a slight increase in blood pressure followed the administration of the extract. Usually, this type of effect is observed in some therapeutic hypotensive drugs and is probably due to vessel abnormalities in the hypertensive state (Godfraind et al., 1986). However, when administered intravenously, the hypotensive effect was observed both in normotensive and hypertensive rats, although it was more accentuated in the latter. The cardiovascular response of hypertensive rats to intravenous injection of 50 mg/kg of the extract showed an effect characterized by an

D.A. lbarrola et al. /rJournal o/ Ethnopharmacology .54 (1996) 7-12

immediate and short lasting hypotension, followed by a transient rise in blood pressure 30 seconds after injection, and finally a slow and persistent hypotension. It took between 45 and 55 rain to return the blood pressure to the initial value. In normotensive animals, the recovery time was less than 10 rain. In summary, our results show a very strong hypotensive activity of S. sisymbri(/blium Lam

I

l

I

Il

I

l

I

.--- 110 la

0

~

.......................~

100

~

.......

(,,)

90

m

~ ~u

80

oo im

250

70 .......................................................................................... I

-I

I

I

I

I

I

I

I

0

1

2

..3

4

,5

6

200

a; 0 ,f,,~ 0 .o

'lime (h)

15O

(a)

100

!

1

I

I

I

!

~-110

50

la o

.~ 100

r~ CONTROLO.1

1.0

10.0

50.0

I>.

100.0

®

(mg/kg, i.v.)

(b)

90

m ti,

0 0

.-.. 250

7O

200 ~

15o

(b)

CONTROLO.1

1.0

I 0 . 0 ,50.0 100.0

I

1

I

I

1

i

[

I

-1

0

1

2

3

4

5

6

(m

Fig. 4. Blood pressure variation in experimentally hypertensive rats after oral administration of S. sisymhri!lblium Lam. extract. (a) Control: vehicle (vJ-7). Extract 10.0 m g k g (O-O); 50.0 mg/kg ( ~ - + ) : and 100.0 mg/kg ( n - B ) , (b) Control: vehicle ( 7 - U ) . Extract 250.0 m g k g ( B - n ) : 500.0 mg/kg { 0 - 0 ) ; and 1000.0 mg/kg (<.',-C). The blood pressure before extract administration was considered to be 100%,. The x-axis represents time course (h) for each dose. Three animals were used for each dose (p.o.). Each point represents the mean ± S.D. *P < 0.05 was considered significant.

(rng/kg. i.v.) Fig. 3. Effect of increasing doses (saline control, 0.1, 1.0, 10.0, 50.0 and 100.0 mg/kg, i.v., respectively) of S. sisymbriifi)lium Lain. on systolic (a) and diastolic (b) blood pressure in hypertensive rats. Each bar represents the mean + S.D. and *P < 0.05 was considered significant.

root extract which may justify its extensive use in folk medicine. Studies are under way to isolate the active principle(s) of the plant and to determine the mechanism of its action.

12

D.A. Ibarrola et al. / Journal of Ethnopharmacologv 54 (1996) 7~ 12

Acknowledgements This work was supported by The Fondo Central de lnvestigaciones of the National University of Asuncion and the Faculty of Chemical Sciences. The authors are grateful to the Japan International Cooperation Agency for the donation of equipment, to Antonio J. Lapa (Departamento de Farmacologia, Escola Paulista de Medicina) for his scientific assistance, and to N. Soria for her work in the botanical classification of the plant. Thanks are also due to Antonio Figueredo for reading the manuscript.

References Burkart, A. (1978) Flora llustrada de Entre Rios (Argentina), Vol. V. Colecci6n Cientifica del Instituto Nacional de Tecnologia Agropecuaria, Buenos Aires, pp. 385 387. Evans, W.C. and Somanabandhu, A. (1980) Nitrogen-containing non-steroidal secondary metabolites of Solanum, Cyphomandra, Lycianthes and Margaranthus. Phytochemistry 19, 2351 2356. Gerber, J.G. and Nies, A.S. (1990) Antihypertensive agents and the drug therapy of hypertension. In: A. Goodman Gilman, T.W. Rail, A.S. Nies and P. Taylor (Eds.), The Pharmacological Basis of Therapeutics. Pergamon Press, New York, pp. 784-813. Godfraind, T., Miller, R. and Wibo, M. (1986) Calcium

antagonism and calcium entry blockade. Pharmacological Reviews 38, 321 416. Gomez-Sanchez, C., Bryan Holland, O. and Murry, B.A. (1977) Mineralocorticoid radioreceptor assay: Application to adrenal-regeneration hypertension. L!/k, Sciences. Pergamon Press, 21, pp. 989 996. Gonzales Torrez, D.M. (1992) Catalogo de Plantas Medicihales O' Alimenticias y Utiles) Usadas en el Paraguay. El Pals, Asuucidn, pp. 312 and 452. Hnatyszyn, 0,. Arenas, P., Moreno, A.R., Rondina, R,V.D. and Coussio, J.D. (1974) Preliminary phytochemical study of Paraguayan medicinal plants. I. Plants regulating fertility from medicinal folklore. Revista de la Soeiedad Cient(B'ea (Paraguay) 14, 23. Lapa, J.A. (1992) Validac~o de plantas medicinais da medicina tradicional. Reuni6n Anual Ripronamed / Quimiea Fina Farmae~;utica C YTED-D. Asuncion, Paraguay, August 23 27, 1992. Maldoni, B.E. (1984) Alkaloids of Solanum sisymhrii/olium. Anales ~& /a Asociaci6n Quimica Argentina 72, 265 267. Martinez-Crovetto R. (1981) Fertility-regulating plants used in popular medicine in Northeastern Argentina. Parodiana I, 97 117. Mazumdar, B.C. (1984) Steroidal sapogenins in two wild species of Solanum. Scienee and Culture 50, 122 123. Staff of the Department of Pharmacology, University of Edinburgh. (1970) Pharmacological Experiments on Intact Preparations. Edinburgh. Churchill Livingstone. Edinburgh, pp. 14 18. Stanton, H.C. (1975) Experimental hypertension. In: A. Schwartz (Ed.), Methods in Pharmacology. Vol. 1. Appleton-Century Crofts, Educational Division, Meredith Corporation, New York~ pp. 125 148.