Chemical and Biological Study of the Essential Oil Isolated from Fruits of Citrus x limonia

Citrus x limonia is an aromatic species, known locally in Ecuador as limón mandarina or limón chino. In the present study, the chemical composition and biological activity of the essential oil isolated from this species were determined. The essential oil was extracted through hydrodistillation. The chemical composition and enantiomeric distribution of the essential oil were determined by gas chromatography. Antimicrobial activity was determined using the broth microdilution method against tree Gram-positive cocci, a Gram-positive bacillus, four Gram-negative bacilli, a fungus, and a yeast. The antioxidant activity was determined through ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods. The spectrophotometric method was used to determine anticholinesterase activity. In the essential oil, thirty-nine compounds were identified, which represented 99.35% of the total composition. Monoterpene hydrocarbons were the most representative group in terms of number of compounds (thirteen) and in terms of relative abundance (91.39%). The main constituents were found to be limonene (57.38 ± 1.09%), γ-terpinene (13.01 ± 0.37%), and β-pinene (12.04 ± 0.63%). Five pairs of enantiomers were identified in the essential oil from fruits of Citrus x limonia. The essential oil presented a minimum inhibitory concentration of 4000 μg/mL against Aspergillus niger. The antioxidant activity of essential oil was weak per the ABTS method, with a SC₅₀ of 1.26 mg/mL. Additionally, the essential oil exhibited moderate anticholinesterase activity, with an IC₅₀ of 203.9 ± 1.03 µg/mL. This study provides the first comprehensive analysis of the chemical composition and biological activities of the essential oil from fruits of Citrus x limonia.