Pharmacognostic and Toxicity Evaluation of the Stem Bark of Tabernaemontana Pachysiphon Stapf. (Apocynaceae)

Abstract

Various claims have been made on the ethno-medicinal uses of the stem bark of Tabernaemontana pachysiphon. It is therefore necessary to establish its pharmacognostic characteristics that will help in its identification and standardization. In this study, the pharmacognostic characteristics (phytochemistry, macroscopy, microscopy, chemo-microscopy, quantitative evaluation, proximate and preliminary Thin Layer Chromatography analyses) and toxicity potential of the stem bark were evaluated using standard methods of analysis. Phytochemical analysis revealed the presence of carbohydrates, reducing sugars, alkaloids, flavonoids, saponins and cardiac glycosides. The stem bark has a bitter taste, flat in shape when fresh and curved when dry, greyish brown in colour on the outer surface and brown on the inner surface. It is longitudinally fissured and lenticels are present. Microscopic examination revealed the presence of cork cells, fibres, sclereids and calcium oxalate crystals. Chemo-microscopic tests showed the presence of lignin, calcium oxalate crystals, mucilage, cellulose and oil. Quantitative parameters (% ^w/_w ± S.E.M) were as follows: moisture content 4.68 ± 0.01; total ash value 8.98 ± 0.12; acid insoluble ash value 0.54 ± 0.01; water soluble ash value 2.05 ± 0.01; alcohol soluble extractive value 3.10 ± 0.01 and water soluble extractive value 0.42 ± 0.01. Proximate analysis of the powdered drug gave 16.59 % protein, 1.90 % fibre, 0.10 % fat, 67.75 % carbohydrate and 4.68 % moisture. Total gross energy was estimated to be 338.26kcal while preliminary thin layer chromatography (TLC) showed three spots. The aqueous extract of the stem bark, at a dose of 5 g/kg, caused neither death nor any observable symptoms of toxicity, after 24 hours. These validated pharmacognostic standards will be useful towards proper identification of a closely related sample of the plant material and in the production of the Nigerian Pharmacopoeia of Nigeria medicinal plants.

Keywords: Tabernaemontana pachysiphon, Stem bark, Pharmacognostic standards, Acute toxicity test

Nigerian Journal of Pharmaceutical Research, Vol. 9 No 1 pp. 63 - 71 (February 2011)