Research Article Open Access
Comparative Acetylcholinesterase Inhibitory Potential of Citrus Essential Oils
Arpana Ashokrao Durge
Department of Biochemistry, Guru Nanak College of Science, Ballarpur, Maharashtra – 442701
16 August 2026
10 August 2026
12 September 2026
Abstract
Evaluation of the in vitro acetylcholinesterase (AChE) inhibitory activity of lemon (Citrus limon) and sweet orange (Citrus sinensis) essential oils (EOs) from peels was carried out. EO were extracted by hydrodistillation. EOs were tested at concentrations ranging from 100 to 1000 µg/mL using the Ellman colorimetric assay. Both oils exhibited concentration-dependent AChE inhibition, with orange oil showing higher activity than lemon oil. Orange oil exhibited 39–87% inhibition, with a calculated IC₅₀ of 147.43 µg/mL, whereas lemon oil showed 10–54% inhibition with an IC₅₀ of 902.01 µg/mL. These findings indicate greater apparent AChE-inhibitory potential of orange essential oil.
Keywords:
Citrus limon, Citrus sinensis, hydrodistillation, essential oil
1. Introduction
Acetylcholinesterase (AChE; EC 3.1.1.7) is a key enzyme in cholinergic neurotransmission, which converts the acetylcholine neurotransmitter into two products namely choline and acetate [1]. AChE activity may also lead to a decrease of AChE levels and consequently cholinergic neurotransmission, rendering the AChE an important pharmacological target, especially in cognitive and neurodegenerative disorders [2,3].
2. Materials and Methods
2.1 Collection and Preparation of Plant Material
Fresh, healthy fruits of lemon (Citrus limon) and sweet orange (Citrus sinensis) were collected from Gadchandur during March. The fruits were cleaned with distilled water for removing the adhering dirt and contaminants. The fruit were peeled manually and cut into small pieces before essential-oil extraction.
3. Results and Discussion
The acetylcholinesterase (AChE) inhibitory activity of lemon (Citrus limon) and orange (Citrus sinensis) essential oils were determined at increasing concentrations. Both essential oils were inhibitory toward AChE and the degree of inhibition was higher in one concentration than in the other concentration for each EO. The inhibitory effect of orange EO was highest over the range of different concentrations than was the lemon essential oil. For orange EO, AChE inhibition ranged from ~39% to 87% between concentrations of 100 µg/mL to 1000 µg/mL, respectively. Concentration-response relationship showed highly logarithmic relationship with the equation y = 20.377 ln(x) − 51.75 with R² value of 0.9876 (Fig 1).
4. Conclusion
The present in vitro study revealed the acetylcholinesterase (AChE) inhibitory activity of both lemon (Citrus limon) and orange (Citrus sinensis) essential oils, which increased with the increasing concentration of the essential oils. The inhibitory activity of orange essential oil (OEO) was significantly higher than that of lemon essential oil (LEO) in the range of 39–87% at the concentrations of 100–1000 µg/mL, and the IC₅₀ was calculated as 147.43 µg/mL. The same concentration range of LEO showed 10-54% inhibition with a calculated IC₅₀ value of 902.01 µg/mL. Therefore, the apparent AChE-inhibitory potency of LEO was slightly lower than that of OEO, with the calculated IC₅₀ being around 6.1-fold higher than that of OEO under the experimental conditions. The concentration-dependent inhibition is supported by the strong logarithmic concentration–response relationships (R² = 0.9876 for OEO and 0.9819 for LEO). The difference between these two essential oils may be related to compositional differences, as well as to possible synergistic interactions between the major and minor volatiles. The reported IC₅₀ values are regression-based values; however, a wider range of concentrations and sigmoidal dose–response analysis are recommended in order to make a more definitive determination of AChE-inhibitory potency.
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