Toxicity and Pharmacognostic Standards for Laxative Properties of Nigerian Cassia sieberiana and Senna obtusifolia Roots

Aims: Research for sourcing laxative crude drugs among Nigerian Cassia/Senna species has continued. The roots of Cassia sieberiana and Senna obtusifolia, reported as mild laxatives, were subjected to pharmacognostic and toxicity investigations to form part of their monographs.

Study Design: This is an experimental laboratory report on toxicological and pharmacognostical investigations that will provide some relevant pharmacopoeial standards for these two plants growing in Nigeria.

Place and Duration of Study: Department of Pharmacognosy Obafemi Awolowo University, Ile-Ife Nigeria, between August, 2010 and January, 2013.

Methodology: Roots of Cassia sieberiana DC. (Caesalpiniaceae). And Senna obtusifolia Irwin and Bernaby (Caesalpiniaceae) were collected from the Eastern (Nsukka), Western (Ile-Ife and Iree) and Northern (Jos) parts of Nigeria during the rainy season. The plant materials were subjected to organoleptic, morphological, phytochemical, physico-chemical and toxicity experiments. The data were analyzed by one-way Analysis of Variance at 95% confidence level. The reference Senna alexandrina (Herb Tea), was purchased from a Pharmacy.

Results: The micro-morphological examination of C. sieberiana and S. obtusifolia roots showed porous vessels, apotracheal parenchyma cells, etc., as valuable diagnostic characters for identification. Free and combined anthraquinones were detected. The toxic oral dose (LD50) for hot infusion of each plant material was found to be > 5000 mg/kg in rats. The histo-pathological examination of C. sieberiana at 500 mg/kg and 1000 mg/kg showed a reversible proliferation of the messenchyma cells of the kidney, mild periportal infiltration of the liver and mild to moderate testicular atrophy in rats while for S. obtusifolia at 500 mg/kg, no observable histo-pathological changes were observed except at 1000 mg/kg, which showed mild periportal infiltration of the liver as also observed with the infusion of the reference senna.

Conclusion: The results have therefore provided some of the valuable data required for the identification, evaluation, quality assurance and safety on the two plants to qualify them for incorporation into the 2nd editions of the Nigerian Herbal Pharmacopoeia (NHP) and the West African Herbal Pharmacopoeia (WAHP).