Inhibitory Activity on Binding of Specific Ligands to the Human Angiotensin II AT₁ and Endothelin 1 ET_A Receptors: Bioactive Benzo[c]phenanthridine Alkaloids from the Root of Bocconia frutescens

Abstract

A bioassay-guided fractionation of the 80 % ethanolic extract from Bocconia frutescens L. roots, showing a dose-dependent inhibitory effect towards both [³ H]-angiotensin II and [³ H]-BQ-123 binding to the human angiotensin II AT₁ and endothelin 1 ET_A receptors, led to an alkaloidal subfraction as the only responsible fraction for the activity of the whole extract. Among the alkaloids present in this fraction sanguinarine and chelerythrine were significant inhibitors of [³ H]-angiotensin II binding (hAT₁ receptor), with IC₅₀ values within the micromolar range. On the contrary, the [³ H]-BQ-123 binding (ET_A receptor) was only weakly inhibited. Moreover, other members of the isoquinoline alkaloid family such as chelidonine and some protoberberine alkaloids exhibited no affinity for the two receptors. The present work shows the possible structure-activity relationship for these benzophenanthridine alkaloids on a screening bioassay using both stably transfected Chinese hamster ovary (CHO) and the human neuroblastoma SK-N-MC cells. Furthermore, the ability of these compounds to block AT₁ and/or ET_A receptors may provide some justification for the traditional use of Bocconia frutescens L. to control hypertension.

Key words

Bocconia frutescens - Papaveraceae - benzophenanthridine alkaloids - hAT₁ receptor - ET_A receptor - CHO cells - SK-N-MC cells

References

• 1 Tulp M. The use of receptor binding, a very specific, high-capacity screening method, in the identification of biologically active components from natural sources. In: Bioassay methods in natural product research and drug development, Bohlin L, Bruhn JG, editors Dordrecht/Boston/London; Kluwer academic publishers 1999: 53-65
• 2 Caballero-George C, Vanderheyden P ML, Solis P N, Pieters L, Shahat A A, Gupta M P, Vauquelin G, Vlietinck A J. Biological screening of selected medicinal Panamanian plants by radioligand-binding techniques.  Phytomedicine. 2001;  8 59-70
• 3 Haynes W G, Webb D J. Endotheline as a regulator of cardiovascular function in health and disease.  Journal of Hypertension. 1998;  16 1081-98
• 4 Timmermans P B, Benfield P, Chiu A T, Herblin W F, Wong P C. Angiotensin II receptors and functional correlates.  American Journal of Hypertension. 1992;  5 221S-35S
• 5 Morton J F. Atlas of medicinal Plants of Middle America. Springfield, Illinois, U.S.A.; Charles C Thomas 1981: 243-4
• 6 Slavik J, Slavikova L. On alkaloids from the leaves of Bocconia frutescens L.  Collection of Czechoslovac Chemical Communication. 1975;  40 3206-10
• 7 Taborska E, Veznik F, Slavik J. Alkaloids from Bocconia frutescens L.  Collection of Czechoslovac Chemical Communication. 1980;  45 1301-4
• 8 Dopke W, Jimenez V, Salas M. Alkaloid content of Bocconia frutescens Linn.  (Papaveracea) Zeitschrift fur Chemie. 1985;  25 105-6
• 9 Tan G, Pezzuto J, Kinghorn D. Evaluation of natural products as inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase.  Journal of Natural Products. 1991;  54 143-54
• 10 Herbert J M, Augereau J M, Gleye J, Maffrand J P. Chelerythrine is a potent and specific inhibitor of protein kinase C.  Biochemical Biophysical Research Communication. 1990;  172 993-9
• 11 Navarro V, Delgado G. Two antimicrobial alkaloids from Bocconia arborea .  Journal of Ethnopharmacology. 1999;  66 223-6
• 12 Heijtmánková N, Walterová D, Preininger V, Šimánek V. Antifungal activity of quaternary benzo[c]phenanthridine alkaloids from Chelidonium majus .  Fitoterapia. 1984;  55 291
• 13 Lenfeld J, Kroutil M, Marsalek E, Slavik J, Preininger V, Simanek V. Antiinflammatory activity of quaternary benzophenanthridine alkaloids from Chelidonium majus .  Planta Medica. 1981;  43 161-5
• 14 Lombardini J B, Props C. Effects of benzophenanthridine alkaloids on the phosphorylation of a 44 kDa protein present in a mitochondrial fraction of the rat heart.  Biochemical Pharmacology. 1996;  51 151-7
• 15 Granger I, Serradeil-le Gal C, Augereau J M, Gleye J. Benzophenanthridine alkaloids isolated from Eschscholtzia californica cell suspension cultures interact with vasopresin (V₁) receptors.  Planta. Medica, 1992;  58 35-8
• 16 Maiti M, Nandi R, Chaudhuri K. Sanguinarine: a monofunctional intercalating alkaloid.  FEBS Letters. 1982;  142 280-4
• 17 Slavik J, Slavikova L. Alkaloide der Mohngewächse (Papaveraceae) XVII. Über neue Alkaloide aus Sanguinaria canadensis L.  Collection of Czechoslovac Chemical Communication. 1960;  25 1667-74
• 18 Marek R, Tousek J, Dostal J, Slavik J, Dommisse R, Sklenar V. ¹H- and ¹³C-NMR study of quaternary benzo[c]phenanthridine alkaloids.  Magnetic Resonance in. Chemistry,1999;  37 781-7
• 19 Tanahashi T, Zenk M. New hydroxylated benzo[c]phenanthridine alkaloids from Eschscholtzia californica cell suspension cultures.  Journal of Natural Products. 1990;  53 579-86
• 20 Vanderheyden P ML, Fierens F LP, De Backer J P, Fraeyman N, Vauquelin G. Distinction between surmountable and insurmountable selective hAT₁ receptor antagonists by use of CHO-K₁ cells expressing human angiotensin II hAT₁ receptors.  British Journal of Pharmacology. 1999;  126 1057-65
• 21 Vanderheyden P ML, Verheijen I, Fierens F LP, De Backer J P, Vauquelin G. Inhibition of angiotensin II induced inositol phosphate production in CHO cells expressing human AT₁ receptors by triacid nonpeptide antagonists.  Pharmaceutical Research. 2000;  17 1482-8
• 22 Fierens F LP, Vanderheyden P ML, De Backer J P, Vauquelin G. Insurmountable angiotensin II AT₁ receptor antagonists: the role of tight antagonist binding.  European Journal of Pharmacology. 1999;  372 199-206
• 23 Cheng Y C, Prusoff W H. Relationship between the inhibition constant (K_i) and the concentration of inhibitor which causes 50 percent inhibition (I₅₀) of an enzymatic reaction.  Biochemical Pharmacology. 1973;  22 3099-108
• 24 Jones R, Harkrader R, Southbard G. The effect of pH on sanguinarine iminium ion form.  Journal of Natural Products. 1986;  49 1109-11
• 25 Lee S S, Kai M, Lee M K. Inhibitory effects of sanguinarine on monoamine oxidase activity in mouse brain.  Phytotherapy Research. 2001;  15 167-9
• 26 Vlietinck A J. Screening Methods for detection and evaluation of biological activities of plant preparations. In: Bioassay methods in natural product research and drug development, Bohlin L, Bruhn JG, editors Dordrecht/Boston/London; Kluwer academic publishers 1999: 37-52