THE EFFECT OF BUILTUP MICROENVIRONMENT AREA ON THE CHEMOTYPE OF Ocimum gratissimum ESSENTIAL OIL HARVESTED FROM THREE LOCAL GOVERNMENT AREA IN EDO STATE

The use of medicinal plants such as Ocimum gratissimum (scent leaf) is widespread, but the therapeutic capability of its essential oil is highly dependent on its chemical profile, or chemotype. Global urbanization introduces specific microenvironmental stresses (e.g., pollution, heat, and soil alteration) that can disrupt plant metabolism, leading to inconsistent oil composition and quality. This study investigated the effect of built-up microenvironments on the chemotype of O. gratissimum essential oil harvested from three distinct Local Government Areas (LGAs) in Edo State, Nigeria: Oredo, Egor, and Ovia North-East. Fresh ocimum. gratissimum leaves were collected from built-up microenvironments in the three selected LGAs. Essential oils were extracted using the Soxhlet method with 99% HPLC-grade hexane, and their chemical compositions were determined using Gas Chromatography–Mass Spectrometry (GC–MS) and Fourier Transform Infrared Spectroscopy (FTIR). GC–MS analysis showed that the essential oil from all three LGAs belonged to a thymol-rich chemotype. However, the concentration of the key active compound, thymol, varied across locations: Egor had the highest thymol content (7.75%), while Oredo was richest in its precursor, o-cymene (12.89%). Ovia North-East exhibited the lowest thymol concentration (5.12%). The presence of high percentages of non-essential oil components (decane and bis(2-ethylhexyl) phthalate) was noted as a potential artifact of the extraction process. FTIR analysis further revealed the consistent presence of nitrogen-containing amine functional groups across all samples, suggesting a stress-induced shift in secondary metabolism. The built-up microenvironment significantly influences the chemical profile of O. gratissimum essential oil. The variation in the o-cymene/thymol ratio and the presence of nitrogenous compounds suggest that local environmental stressors (such as pollution or soil conditions) may disrupt the final stages of the monoterpene biosynthetic pathway. These findings highlight the critical need for standardizing growing conditions in pharmacologically driven cultivation to ensure a consistent and high-quality essential oil chemotype.