Comparative Profiling of Solvent-mediated Phytochemical Expressions in Ocimum gratissimum and Vernonia amygdalina Leaf Tissues via FTIR Spectroscopy and Colorimetric Assays

Abstract

Objective: The beneficial role of extraction solvents is often ignored, yet very important in enhancing the therapeutic potential of plant extracts. This study was carried out to comparatively characterize and profile the bioactive phytochemical compounds expressed in different solvent-fractions of Ocimum gratissimum and Vernonia amygdalina leaf extracts using both colorimetric phytochemical screening assays and Fourier transform infrared (FTIR) spectroscopy. Methods: Qualitative colorimetric assays were carried out on different solvent-fractions of leaf tissue extracts from both plants to determine the comparative expression profiles of bioactive phytochemical compounds with medicinal importance such as alkaloids, anthraquinones, cardiac glycosides, flavonoids, phlobatannins, tannins, terpenoids, saponins, and reducing sugars. FTIR spectroscopy was used to characterize, and profile the presence of these compounds based on functional groups such as alcohols (O-H), saturated hydrocarbons (C-H), aliphatic fluoro (C-F), bromo (C-Br) and chloro (C-Cl) compounds, organic sulfates (S=O), esters, ethers, carboxylic acids (C-O), aromatic amines, methane nitriles (C-N), ketones, aldehydes, quinones (C=O), sulfur compounds (C=S), primary and secondary amines (N-H) with bioactive properties in the different solvent-fractions. Results: Data were generated for methanol, n-hexane, ethyl-acetate, n-butanol and aqueous solvent-fractions of Ocimum gratissimum and Vernonia amygdalina leaf extracts. We have generated solvent-mediated phytochemical expression profiles for leaf tissue extracts of both plants based on the phytochemistry of their secondary metabolites. The methanolic solvent-fraction expressed the most phytochemicals in both plants. Conclusion: This study has revitalized the importance of extraction solvents in optimizing phytochemical bioavailability in plant tissues. This may be responsible for variation in medicinal and biological activities reported in prior studies.