Phytochemical Screening, Acute Toxicity and Anti-Rabies Activities of Extracts of Selected Ethiopian Traditional Medicinal Plants

Background: Rabies, endemic in most African and Asian countries, is a viral zoonosis that causes an estimated 59,000 human deaths a year, despite the existence of safe and effective vaccines. In most developing countries people believe to cure rabies with different traditional and religious treatment rather than seeking effective post exposure prophylaxis. Purpose: To investigate the phytochemical constituents, acute toxicity and antirabies activity of crude extracts of the leaves of Justicia schimperiana and Ricinus communis and the stem bark of Croton macrostachyus. Methods: To test the presence of various phytochemicals, standard procedures were used. For the determination of acute toxicity and in vivo antirabies activities, Organization for Economic Corporation and Development (OECD) Guideline No.423 was used. Different concentrations of extracts (0.4, 0.8, 1.6, 3.2, 6.4 and 12.8 mg/ml) were tested for their cytotoxic effect on Vero cells through 3-(4, 5-Dimethylthiazol-2-yl)-2, 5Diphenyltetrazolium Bromide (MTT) assay. The in vitro antirabies assay was carried out based on the minimal cytotoxic concentration of extracts. Results: The phytochemical screening result has revealed the presence of alkaloids, flavonoids, phenols, steroids, tannins and terpenoids in all plant extracts screened but lack saponins. All the extracts were slightly toxic in Swiss albino mice model but non cytotoxic in Vero cell lines. The antirabies assay result showed that all plant extracts had a moderate to good antirabies potential. The methanol extracts exhibited higher antirabies activity compared to the other extracts under investigation. Conclusion: The present study concluded that the studied plants have possessed different phytochemicals that helps in their antirabies potential. Utilization of these pharmacological properties involves further investigation of these active ingredients by implementation techniques of extraction, purification, separation, crystallization and identification.