psychopharmacological studies on echitovenidine

Pharmacological Research Communications, Vol. 8, No. 2, 1976 159

PSYCHOPHARMACOLOGICAL STUDIES ON ECHITOVENIDINE

S.K.Bhattacharya and A.B.Ray Departments of Pharmacology and Medicinal chemistry,

Institute of Medical Sciences, Banaras Hindu University, Varanasi

and S.R.Guha

Indian Institute of Experimental Medicine, Calcutta, India.

Received 26 March 1975

mmwr Echitovenidine, the major fruit alkaloid of Alstonia

venenata, showed monoamine oxidase inhibitor activity by both

in vivo and in vitro tests. The experimental data may rationalise -w --

the use of the plant for mental disorders in the traditional

Indian system of medicine.

INTRODUCTION

The fruits of Alstonia venenata R.Br. (Pam. Apocynaceae)

are used for the treatment of insanity and epilepsy in the ancient

Indian system of medicine, Ayurveda (Chopra et aJ.,l956). An enquiry

with local Ayurvedic physicians reveals that the dried fruit powder

is used in a variety of mental diseases which resemble the modern

concept of affective disorders. The fruits of A.venenata have so

far yielded, on chemical investigations, a monoterpene base (Ray

and Chatterjee,l968), seven indole alkaloids (Das et a1.,1966;

Majumdar et a1.,1972; Chatterjee et a1.,1973) and two non-nitro-

genous constituents, S-amyrin and ursolic acid (Pandey and Ray,197:3)

160 Pharmacological Research Communications, Vol. 8, No. 2, 1976

Echitovenidine, the major alkaloids1 constituent of the fruits,

possesses a vincadifformine skeleton (Das et al.,lY66j, a feature

common in all indole bases isolated from this source.

Echitovenidine

No pharmacological study has been reported on any of

these alkaloids. This communication concerns the psychopharm$-

cological activity of echitovenidine.

MATERIAL AND METHODS

Studies were conducted on inbred strains of albino rats

(100-150 g), albino mice (20-30 g) and mongrel dogs (lo-15 kg).

The following methods were used for in vivo studies:-

(A) Primary observational test in rats and mice (Irwin,1964).

(B) Effect on hexobarbital (100 mg/kg i.p.) sleeping time in mice

(Voith and Herr,l969).

(C) Effect on reserpine (2.5 mg/kg i.p.) induced sedation and

ptosis in mice (Turner and Hebborn,l971).

(D) Effect on amphetamine (10 m&kg i,p.j toxicity in aggregated

mice (Trepanier et a1.,1969).

(E) Effect on DOPA (100 mg/kg i.p.) induced behavioural response

in mice (Turner and Hebborn,l971).

(F) Effect on 5-hydroxytryptophan (5-HTP, 50 mg/kg i.p.) induced

head twitch response in mice (Corne et a1.,1963).

(G) Effect on tryptamine (5 mg/kg i.p.) induced clonic convulsions

in rats (Tedeschi et a1.,1960).

(H) Effect on subanalgesic dose (2 mg/kg i.p.) of morphine in


rats (Bhattacharya et &.,1971). Analgesic activity was tested

by the rat tail-hot wire technique (Davies et e.,1946).

(I) Effect on sub-anticonvulsant dose (2.5 mg/kg i.p.) of diphenyl-

hydantoin in rats (Bhattacharya et al.,1915 a ). Anticonvulsant

activity was tested by the maximal electroshock induced seizure

method (Swinyard et a1.,1952).

(J) Effect on anaesthetised (pentobarbital sodium, 35 mg/kg i.p.)

dog's carotid blood pressure and respiration. Drugs were adminis-

tered through cannulated femoral vein.

(K) Acute toxicity studies in mice. LD50 was calculated by the

method of Miller and Tainter(l944).

Solution of echitovenidine in dilute acetic acid was

adjusted to pH 5 and administered i.p., unless otherwise mentioned.

Control animals received equivalent volume of distilled water,

rendered pH 5, by the same route. Echitovenidine was used in a

dose of 50 mg/kg, with a pre-treatment time of 60 min, unless

otherwise stated. Ten animals have been used for each drug treated

and control group. Student's 't' and 'chit square tests of signi-

ficance have been used at appropriate places.

In vitro determination of monoamine oxidase inhibitor

activity was done by the method of Green and Haughton (1961) as

modified by Guha (1966), using rat brain mitochondria as the source

of enzyme and tyramine as substrate.

RESULTS AND DISCUSSION

Echitovenidine produced initial signs of central stimula-,

tion in rats and mice, characterised by increased motility, piloerec

tion, startle response, compulsive gnawing, tremors and hurried

respiration. After 20-25 min, signs of central depression appeared,

characterised by sedation, diminished motility, passivity and


clumping together of the animals. The excitatory phase was more

marked in mice while the inhibitory phase was more pronounced in

rats. In higher doses (100 mg/kg), some mice exhibited clonic

convulsions, which was more accentuated in animals pre-treated

with nialamide (25 mg/kg i.p.) or imipramine (20 mg/kg i.p.).

Echitovenidine significantly (P(O.01) potentiated hexobarbital

sleeping time. The mean sleeping time, in min + S.E.M., in the

control group was 20 2 4.5, whereas in the drug treated group

it was 56 2 6.8. The drug markedly antagonised reserpine induced

sedation and ptosis, when given before reserpine but failed to

reverse teserpine effects when administered after reserpine.

The drug significantly (PC 0.05) potentiated the lethal effect

of amphetamine in aggregated mice. Mortality, observed over a

period of 24 hr, in the control group was 20X, while in the drug

treated group mortality was 80%. The drug produced fighting

behaviour, tremors, piloerection and circling movements in the

drug pretreated DOPA group of mice, while these signs were minimal

or absent in the control DOPA group. Echitovenidine markedly

potentiated 5-HTP induced head twitch response. In the control

5-HTP group, head twitch was absent, whereas in the drug pre-

treated group, the number of head twitches seen at 19-21, 23-25

and 27-29 min after 5-HTP administration, was 2/min. The drug

significantly (PC 0.05) potentiated the incidence of convulsions

produced by tryptamine. In the control tryptamine group, incidence

of convulsion was lo%, whereas in the drug pretreated group,

convulsions were seen in 60% rats. Echitovenidine significantly

(P <O.OOl) potentiated the analgesic effect of a subanalgesic

dose of morphine. The mean latent period of tail flick response,

in set + S.E.M., was 10.2 + 0.96 in the control morphine group,


while in the drug pretreated group it was 25.3 + 3.1. The drug

did not have any analgesic effect per se in the dose used. The

drug also significantly potentiated (PC 0.05) the anticonvulsant

effect of a sub-anticonvulsant dose of diphenylhydantoin. In the

control diphenylhydantoin group anticonvulsant action was 0%,

whereas in the drug pretreated group, the anticonvulsant effect

was 60%. The drug had no anticonvulsant effect per se in the dose

used. Echitovenidine produced a transient depressor response in

anaesthetised dog, with no significant effect on respiration, in

dose of 10 mg/kg. However, on increasing the dose to 50 mg/kg,

there was a profound fall in blood pressure, of prolonged duration,

accompanied with depression of respiration. The drug did not

significantly alter the pressor responses of adrenaline and

nicotine nor the depressor responses of acetylcholine and histamine

The LD50 of echitovenidine in mice was 126 t 23 mg/kg i.p.

A comparitive evaluation using the known monoamine

oxidase inhibitor nialamide, as reference standard, showed that

the pharmacological profile of activity of echito-venidine was

qualitatively similar to nialamide in all the experimental para- .3 meters used in the study. Nialamide was however, 1% to 2 times

more potent than echitovenidine.

Echitovenidine, in concentrations of 3~10'~ and 3~10'~ M,

produced 47% and 24 % inhibition of rat brain mitochondrial

monoamine oxidase, respectively.

Monoamine oxidase inhibitors, by virtue of their inhibi-

tory effect on degredation of brain monoamines, elevate the

availability of these amines at central monoaminergic receptor

sites. Thus, they are known to prevent monoamine depletion by

reserpine. The reserpine syndrome in experimental animals as an


analogue of clinical depression, is compatible with the catechol-

amine hypothesis of affective disorders (Schildkraut,l965). of the

two classes of antidepressants, monoamine oxidase inhibitors can

antagonise reserpine effects in experimental animals only on pre-

treatment, whereas tricyclic antidepressants show anti-reserpine

effects both on pretreatment and also when administered after

reserpine effects are well established (Turner and Hebborn,l971).

The pharmacological actions of several classes of centrally active

drugs are known to be potentiated by monoamine oxidase inhibitors,

viz. barbiturates, morphine and diphenylhydantoin. The mechanism

of action of these drugs probably involve central monoaminergic

transmission (for literature see Mantegazzini,l966; Calcutt et &.,

1972; Meyer and Frey,1973; Bhattacharya et al.,1975 a, b). Similarly,

the central effects of monoamine precursors like POPA and S-HTP

are also potentiated by monoamine oxidase inhibitors (Turner and

Hebborn,l971) . It is generally agreed that the central pharmacolo-

gical actions of amphetamine involves release of catecholamines

from central adrenergic neurones (Hanson,1966). As such, mono-

amine oxidase inhibitors are expected to potentiate the central

actions of amphetamine (Turner and Hebborn, 1971). Likewise, the

potentiation of central effects of tryptamine is well documented

(Tedeschi et al., 1960). Apart from their effects on reserpine

syndrome, monoamine oxidase inhibitors can also be experimentally

differentiated from tricyclic antidepreesants, by the potentiating

effect of the latter on exogenously administered adrenaline and

noradrenaline. Monoamine oxidase inhibitors have little effect on

exogenous catecholamines (Turner and Hebborn,l971).

The results of the in vivo studies thus clearly categorise

echitovenidine as an antidepressant of the monoamine oxidase type.


This is evidenced by its ability to potentiate the pharmacological

actions of hexobarbital,amphetamine,DOPA,5-HTP,tryptamine,morp~ine

and diphenylhydantoin. This is further substantiated by its ability

to antagonise reserpine effects on pretreatment but its failure to

show an anti-reserpine effect when administered after reserpine.

The inability of echitovenidine to potentiate pressor response of

adrenaline, provides further evidence that it does not fall under the

category of imipramine like antidepressants.

The in vivo studies are confirmed by the in vitro demonst- --

ration of monoamine oxidase inhibitor activity of echitovenidine.

The psychopharmacological activity of the alkaloid may

explain the reported use of the plant for mental disorders in the

traditional system of medicine in India.

ACKNOWLEDGEMENT

The authors are grateful to Prof.(Mrs.) A.Chatterjee,

Calcutta University, for her kind interest,

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psychopharmacological studies on echitovenidine

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