Phytochemical composition, cytotoxicity and toxicological studies of rosmarinus officinalis, catharanthus roseus and myrsine africana crude extract

Abstract

Natural medicinal products have gained recognition worldwide in the treatment and control of diseases. One of the major concerns is the lack of adequate pharmacological and toxicological data to support their use. Catharanthus roseus is a commonly used plant especially in the control of diabetes. Myrsine africana is traditionally used as veterinary and human anthelmintic while Rosmarinus officinalis is used as a spice for it has high antioxidant and other therapeutic properties. This study was carried out on the crude extracts of leaves of C.roseus, R. officinalis and dry seeds of M. africana to screen for their phytochemical composition. Oral acute toxicity and the effects on hematological and biochemical parameters of each of the plant extracts at doses of1000 and 5000 mg/kg body weight were determined. Male albino Wistar rats were used as the Organization for Economic Co-Operation and Development (OECD) guidance document 423 recommends use of one sex animals. A control group was given distilled water. A 28 day repeated oral administration of freeze dried aqueous extract of R. officinalis on four groups of Wistar rats at dosages 0, 500, 1500 and 3000 mg/kg body weight (bwt) was carried out to evaluate the plants sub-acute toxicity. The cytotoxicity and lethality effects on the brine shrimps (Artemia salina) in four organic and an aqueous extracts of each of the three plants was studied using concentrations 10, 100, 1000 µg/ml of each extract as described by Meyer et al., 1982. Brine shrimp median lethal concentration (LC50) for each extract was calculated using a regression line of probit against log concentration. The phytochemical analysis showed presence of 5 types of bioactive compounds namely terpenoids, tannins, anthraquinones, alkaloids and reducing sugar in Catharanthus roseus. Terpenoids, tannins, flavonoids, saponins and reducing sugars were also found present in Myrsine africana extract. Rosmarinus officinalis extract contained terpenoids, tannins, cardiac glycosides, flavonoids, reducing sugars and saponins. The median lethal dose (LD50) of the aqueous extracts for each of the three plant extracts in albino Wistar rats was estimated to be > 5000 mg/kg body weight. Alanine aminotransferase (ALAT), aspartate aminotransferase (AST), urea, White blood cells (WBC) and mean corpuscular volume (MCV) were significantly elevated in the groups treated with. C. roseus extract (p<0.05), but thrombocytes and percentage weight gain were significantly reduced in these groups. Red blood cells (RBC), packed cell volume, (PCV), mean corpuscular hemoglobin concentration, (MCHC), AST and serum urea were significantly elevated in the groups given M. africana extract. ALAT both at 1000 and 5000mg/kg body weight of R. officinalis treated groups were significantly reduced at 48 hours but at 14 days they had normalized to baseline values. Sub-acute toxicity testing of R. officinalis aqueous extract showed no significant difference of hematological and biochemical parameters at 500 and1500 mg/kg body weight both at 14 and 28 days testing. Significant elevation of WBC, percentage lymphocytes and ALAT at 3000 mg/kg body weight when compared with the control was reported both at days 14 and 28 testing (P < 0.05). Methanolic extracts of M. africana and C. roseus showed very strong cytotoxicity to brine shrimps with LC50 of < 10 µg/ml. Aqueous extract of M. africana did not cause significant cytotoxicity against the brine shrimp, with LC50 > 1000 µg/ml. It was concluded that the phytochemicals present in each plant extracts may be responsible for bioactivity effects that were recorded. It was also concluded that Myrsine africana and Catharanthus roseus are likely to cause acute renalhepatotoxicity and hematopoietic system toxicity at oral concentrations that were tested. This is explained by the elevated biochemical parameters (AST, ALAT, and urea) and the significantly altered hematological parameters. It was recommended that these plants should be used with care and at lower concentrations. Sub-acute and chronic toxicity testing of these plants is recommended in order to clearly establish the effects of repeated doses. Methanolic seed extract of M. africana is likely to have antitumor and insecticidal properties due to its high cytotoxicity and isolation of the constituent bringing this effect is recommended. The results of .R. officinalis toxicity studies indicate that the plant is not acutely toxic but prolong toxicity studies are recommended to confirm the safety of the plant.