Comparative Phytochemical, FTIR and GC–MS Characterization of Aqueous and Ethanolic Leaf Extracts of Azadirachta indica, Psidium guajava and Ocimum gratissimum
Abstract
Medicinal plants are important sources of bioactive compounds with potential pharmaceutical applications. This study comparatively evaluated the extraction yield, phytochemical composition, Fourier Transform Infrared (FTIR) characteristics, and Gas Chromatography–Mass Spectrometry (GC–MS) profiles of aqueous and ethanolic leaf extracts of Azadirachta indica, Psidium guajava, and Ocimum gratissimum were collected from Kaduna state, Nigeria. Leaf powders were extracted separately by cold maceration using distilled water and ethanol. The extracts were subjected to qualitative and quantitative phytochemical analyses, FTIR spectroscopy, and GC–MS characterization using standard analytical procedures. Ethanolic extraction produced higher yields (9.4–11.3%) than aqueous extraction (7.6–8.2%) across all plant species. Phenols, flavonoids, tannins, alkaloids, saponins, and terpenoids were detected in all extracts, although their concentrations varied among plant species and extraction solvents. Ocimum gratissimum exhibited the highest phenolic (11.21 ± 1.62 mg/g) and flavonoid (6.13 ± 1.35 mg/g) contents, whereas Psidium guajava contained the highest tannin concentration (5.74 ± 1.72 mg/g). FTIR analysis confirmed the presence of characteristic functional groups associated with phenolics, alcohols, esters, aromatic compounds, and other oxygenated metabolites. GC–MS analysis identified diverse bioactive constituents, predominantly fatty acids, fatty acid derivatives, long-chain hydrocarbons, esters, and related compounds with documented antimicrobial and antioxidant activities. The observed variations in extraction yield and phytochemical contents among plant species and extraction solvents were statistically significant (p < 0.05) based on one-way ANOVA. The findings demonstrate that ethanol is a more efficient extraction solvent than water and highlight the rich phytochemical diversity of these medicinal plants.