Full Length Research Paper

Antithrombotic/anticoagulant and anticancer activities of selected medicinal plants from South Africa

Nalise Low Ah Kee¹, Nandipha Mnonopi¹, Hajierah Davids², Ryno J. Naudé¹ and Carminita L. Frost¹*

¹Department of Biochemistry and Microbiology, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa.

²Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa.

*Corresponding author. E-mail: carminita.frost@nmmu.ac.za. Tel: +27 41 5044123. Fax:  +27 41 5042814.

Abbreviations: S2238, H-D-phenylalanyl-L-pipecolyl-p-nitroanilide dihydrochloride; DMSO, dimethyl sulfoxide; PVPP, polyvinylpolypyrrolidone; BSA, bovine serum albumin; DMEM, Dulbecco’s Modified Eagles Medium; FBS, fetal bovine serum; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; IC₅₀, 50% inhibition.

Accepted 2 January, 2008

Nine plants available in the Eastern Cape Province of South Africa were tested for antithrombotic and/or anticoagulant activity.  Organic (methanol) and aqueous (distilled water) extractions were performed on the various plant parts. The thrombin assay and clotting time assays (thrombin-induced and CaCl₂-induced) were utilised. Several extracts displayed activity, but in most cases this was due to the presence of tannins. Only the aqueous extracts displayed activity after tannin removal. The Sutherlandia frutescens leaf extract displayed antithrombotic activity, with an IC₅₀ value of 2.17 mg/ml. Gloriosa superba and Zantedeschia aethiopica leaf extracts displayed anticoagulant properties by inhibiting thrombin-induced clotting, with IC₅₀ values of 2.97 and 3.05 mg/ml, respectively.  The Leonotis leonurus root extract was found to decrease the CaCl₂-induced clotting time by 50% at 8.88 mg/ml.  A decrease in this value accompanied by a decrease in fibrin formation was preferable for the CaCl₂-induced assay, since decreased fibrin formation may have a role in the prevention of cancer metastasis.  As tannins were found to contribute minimally to the anticoagulant effect of L. leonurus, the cytotoxicity potential of the extracts of this species against five cell lines was determined.  Only the organic extract yielded significant cytotoxity.

Key words: Antithrombotic, anticoagulant, anticancer, medicinal plants.