Pharmacognostic Evaluation of the Leaves of Thurnbegia laevis Nees (Acanthaceae)

Thurnbegia laevis Nees. belong to the Acanthaceae family. It is used in folklore medicine for the management of diabetes, piles, joint pains as well as skin related problems. This study aims to evaluate the leaves of the plant by employing the quality control parameters. The leaves of T. laevis were collected, identified, air-dried, pulverized and stored in glass bottles. Standard procedures were used to carry out microscopy on the fresh leaves, micromeritics, chemomicroscopy, fluorescence analysis, soluble-extractive values, moisture contents and ash values using powdered samples of the leaf. Methanol extract of the leaf was used to conduct GC-MS analysis. The result showed that the leaf was amphistomatic with diacytic stomata on both surfaces. The micromeritic studies showed that the leaf had an angle of repose of 37.47ᵒ, Carr’s Index of 23.01% and Hausner’s ratio of 1.3. Water-soluble, ethanol-soluble and methanol-soluble extractive values were 21%w/w, 10%w/w and 11%w/w, respectively. Fluorescence analysis of the leaf showed different colours indicating the presence of different phytochemicals. The moisture content, total ash, acid-insoluble and water-soluble ash values were 5.31%w/w, 15.18%w/w, 2.7%w/w and 5.6%w/w, respectively. Chemomicroscopy of the leaf powder showed the presence of mucilage, lignin, starch, cellulose and protein while, oil and calcium oxalate crystals were absent. The GC-MS analysis showed the presence of thirty-five (35) phytochemicals with compounds like n-Hexadecanoic acid, 9,12,15-Octadecatrienoic acid, Vitamin E, Stigmasterol, Supraene and, Benzoic acid. These compounds have antioxidant, anticonvulsant, antiserum, antifungal, hypoglycaemic, antimicrobial, anti-inflammatory and larvicidal activities. The results stated could be used to establish standards for the authentication of the fresh and powdered drug leaf products of Thunbergia laevis.