Jouraal of E~~~p~a~~o~gg, 31 (1991) 391- 394 Elsevier Scientific Publishers Ireland Ltd.

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Short ~o~unicatio~

STUDIES ON ARRUS PRECATORIUS SEEDS. I: UTEROTONIC ACTIVITY OF SEED OIL

O.F.C. NWODO

Biochemistry Department. University of Nigeria, Nsukka (Nigeria)

(Accepted September 3, 1990)

Introduction

Ethanolie extracts of the seeds of Abms ~ecut~~~ L. (Legumi~osae) are us- ed widely in Igbo-Nigeria folk medicine as an oxytocie. The evaporated alcoholic extract is administered in the form of a vaginal pessary to induce abortion (Nwodo, 19831. Previous investigations have shown the presence of the follow- ing uterotonic agents: peptides (Saha et al., 19611, a pyridinium glycoside and indolyl glycosides (Nwodo, 19811. It is not clear whether the peptides reported by Saha et al. (19611 include abrin, a toxic dimeric glycoprotein (Lin et al., 1969a) which exerts its toxic effects by inhibiting 60s ribosomal sub unit GTPase ae- tivity (Benson et al., 19751 which in turn inhibits protein synthesis fLin et al., 1969a; Olsnes and Pihl, 19721. Abrin is not extractable in organic solvents (Hum- phrey% 19691 and its toxicity is lost after boiling for 30 min (Lin et al., 1969b) or after tryptic digest fLin et al., 19701.

It is well known that certain prostaglandins can be used to induce abortion and labour. Because the lipids extractable from A brus seeds contain some C,- C,, unsaturated carboxylic acids inlcuding linoleic acid (Lefar et al., 19681 from which precursors for prostaglandin synthesis are formed, it is possible that lipids from the seeds could be uterotonic, Therefore, this possibility was in- vestigated using gravid and also primed virgin uteri.

materials and Methods

Plant materials The seeds of Abrus precatorius were collected from Ukehe, Anambra State,

Nigeria between December and February, 1985186 and were authenticated at the source by Dr. C.O.C. Agwu of the Botany Department, University of Nigeria, Nsukka.

0373-3741/$03.50 0 1991 Elsevier Scientific Publishers Ireland Ltd. Published and Printed in Ireland

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A 25 g quantity of the crushed seeds of Abrus precatorius was soaked in 5 volumes (w/v) of chloroform/methanol (2:ll for 5 h. The extract was filtered through Whatman No. 4 filter paper and then shaken with 0.2 volume of water. The lower chloroform layer was run off and evaporated to dryness. This is the total lipid extract and is termed here as the seed oil (yield = 3.1% w/w in terms of starting materials).

Animals Male and female guinea pigs (300-500 gl and inbred Wistar albino rats

(150-250 gl were used. The rats were fed with standard Pfizer diets and were allowed free access to water. Female animals were either pregnant or virgins primed with 0.1 mglkg diethylstilboestrol 18 h before use.

Assay of biological activity Segments of relevant tissues, 2-3 cm in length, from freshly killed animals

were suspended in an organ bath maintained at 37°C and containing modified Krebs solution (Batting and Salzmann, 19741 gassed with 5% CO, in 0,. Guinea pig ileum was stimulated electrically by a pair of silver electrodes attached to the inner walls of the bath at 0.1 Hz at supramaximal voltage and 0.9 ms pulse width. In some experiments, tissues were superfused by modified Krebs fluid.

Results

A physical dispersion of the seed oil in modified Krebs solution produced no effect on the electrically stimulated guinea pig ileum in concentrations lower than 1.8 mglml, but, at higher concentrations, it enhanced the twitches.

When administered via the bath or superfused, the oil induced dose-dependent contractions of both gravid and primed virgin uteri. The contractions were atropine- (3.0 x 10-8M) resistant but were blocked by indomethacin (1.4 x 1O-5 Ml. The sensitivity of the tissue to the oil could be restored by sub-effective doses of PGE,(O.l-1.0 x lo-lo M; see Fig. 1).

Discussion

This investigation revealed that Abrus seed oil contains an agent that is uterotonic and which may contribute to the use of the seed extracts as an ox- ytocic in folk medicine. The reduction of oil-induced activity, in the presence of indomethacin, a prostaglandin synthetase inhibitor, suggests the involvement of some cycle-oxygenase product in the activity. Because contractions of the tissue to the oil were restored by sub-effective doses of PGE, in the presence of in- domethacin, it may be concluded that the oil either has PG synthesis substrate activity or requires prostaglandins for action. Since the oil contains a mixture of C,-C,, unsaturated carboxylic acids (Lefar et al., 19681 substrate activity is more plausible. This possibility is now under investigation in this laboratory.

The resistance of this activity to atropine blockage and the inability of the

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fndomethacin

.

Fig. 1. The effect of Abrus seed oil on superfused primed rat uterus. The seed oil (Ab, 3.6 mg), like oxytoein (Ox, 5 mUnits) and PGE, (5 ng), induced contractions of the primed rate uterus. Contrae- tions to Ox and Ab were reduced greatly by indomethacin (1.4 x 1O’5 M) but were restored by a sub-effective concentration of PGE, (1 x 10“’ M) in the presence of indomethaein.

oil to inhibit twitches of the eiectrically-stimulated guinea pig ileum appear to rule out the involvement of muscarinic receptors and the intrinsic spasmolytic reported by Nwodo and Botting (1983). In addition to the uterotonic agents reported by Saha et al. (1961) and Nwodo and Botting (19831, it appears that the oil-based substance may be another agent contributing to the oxytocic property of the seeds.

References

Benson, S., Olanes, S., Pihl, A., Skrove, J. and Abraham, A.K. (19’75) Mechanism of protein-synthesis inhibition of GTP hydrolysis site on the 60s ribosomal sub unit. ~~ropeu~ Joann of ~~chern~t~ 59, 573 - 580.

Botting, J.H. and Salzmann, R. 11974) The effect of indomethacin on the release of prostaglandins and acetylcholine from guinea pig isolated ileum at rest and during field stimulation. Btitish Journal of Pharmacology 50, 119-124.

Humphrey% D.J. (1969) Toxic factors of the seeds ofdbus praecatotius. Phytochemistry 8,2397-2400. Lefar, M.S., Fireston, D., Coleman, E.C., Brown, N. and Shaw, D. (1968) Lipids from the seeds of

Abrus ~Tec~to~us. Journd of ~h~~aeeut~c~~ Sciences 57, 1442- 1444. Lin, J.-Y., Chen, C-C., Lin, L.-T. and Tung, T.-C. (1969a) Toxic actions of abrin (protein). T’a&W&

I Hsueh Hut Tsa Chih 68, 322-324. Lin, J.-Y., Chen, C.-C.. Lin, L.-T. and Tung, T.-C. (1969b) Inhibitory effect of abrin on Ehrlich ascites

tumor. Tai-Wan I Hsueh Hui Tsa Chih 68, 522-525. Lin, J.-Y., Kao, C.L. and Tung, T.-C. (1970) Effect of trypie digestion on the toxicity of abrin. Thi-

Wan I Hsueh Hui, Tsa Chih 69, 61-63. Olsnes, S. and Pihl, A. (1972) Inhibition of peptide chain enlongation. Nature. London 238,459-461. Nwodo, O.F.C. (1981)Elucidation of the Nature of Some Pha~acoZogically Active Substances Ex-

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tractable from the Seed of Abrus precatotius. Doctoral dissertation, University of London, London, U.K.

Nwodo, O.F.C. and Botting. J.H. (1983) Uterotonic activity of extracts of the seeds of Abrus precatorius. Planta Medica 47, 230-233.

Saha, J.C., Savini, E.C. and Kasinathan, S. (1961) Ecbolic properties of Indian medicinal plants. Zn- dian Journal of Medical Research 49, 130- 150.