Pharmacognostic study and peptidomic analysis of the leaves of Nigerian Rauvolfia vomitoria Wennberg (Apocynaceae)

Abstract

This study was aimed at documenting some pharmacognostic and peptidomic standards on the leaf of Nigerian species of Rauvolfia vomitoria Wennberg (RVM). Using standard methods, the fresh and dried pulverized leaves of R. vomitoria were standardized macroscopically and microscopically, in addition to the physiochemical evaluation and MALDI TOF/TOF-guided peptidomic screening of the aqueous extracts of the leaf. The leaf is simple, elliptical shaped, crenated margin which is acute. The leaf presented a hexagonal shaped epidermal cell on both sides with anomocytic stomata only on the abaxial surface making it hypostomatous while stomata number and index are 15 – 16 – 18 and 24 – 25 – 26, respectively. The transverse section of the leaf through the midrib suggests that the vascular bundles are conjoint, collateral and closed. Moisture content, total ash, acid insoluble ash, water soluble ash, sulphated ash, water soluble and alcohol soluble extractives were as follows; 7.7 ± 1,5, 4.9 ± 0.7, 1.2 ± 0.8, 4.1 ± 0.2, 4.8 ± 0.9, 3.9 ± 0.9, 8.1 ± 1.7w/w%, respectively. Peptidomic analysis revealed the abundant expression of nature-derived knottin-like peptides with a mass range of 3.1 kDa – 3.7 kDa. Knottin peptides have been reported to perform defense roles in host plants; since they are not ubiquitously distributed in planta, their detection in RVM could be useful in the proper identification of the plant and in RVM chemosystematics. Findings from this study has unveiled some important macroscopic, microscopic and physicochemical standards as well as a new peptidomic phytochemical standard helpful in the proper identification in addition to ensuring the efficacy and safety of the leaf of R. vomitoria.