Evaluating 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 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: C. sieberiana root was relatively non-toxic at lower doses while its toxicity at high doses
on the kidney, liver and testis were reversible following withdrawal of the drug. 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).