Supercritical CO2 assisted extraction of essential oil and naringin from Citrus grandis peel: in vitro antimicrobial activity and docking study

Abstract

The extraction of bioactive compounds, including essential oils and flavonoids, using organic solvents is a significant environmental concern. In this work, waste C. grandis peel was the ingredient used to extract essential oil and naringin by conducting a supercritical CO₂ technique with a two stage process. In the first stage, the extraction with only supercritical CO₂ solvent showed a significant enhancement of the D-limonene component, up to 95.66% compared with the hydro-distillation extraction (87.60%). The extraction of naringin using supercritical CO₂ and ethanol as a co-solvent was done in the second stage of the process, followed by evaluating in vitro antimicrobial activity of both the essential oil and naringin. The essential oil indicated significant activity against M. catarrhalis (0.25 mg ml⁻¹), S. pyogenes (1.0 mg ml⁻¹), S. pneumoniae (1.0 mg ml⁻¹). Whilst naringin gave good inhibition towards all tested microbial strains with MIC values in the range of 6.25–25.0 μM. In particular, naringin exhibited high antifungal activity against T. rubrum, T. mentagrophytes, and M. gypseum. The molecular docking study also confirmed that D-limonene inhibited bacterium M. catarrhalis well and that naringin possessed potential ligand interactions that proved the inhibition effective against fungi. Molecular dynamics simulations of naringin demonstrated the best docking model using Gromacs during simulation up to 100 ns to explore the stability of the complex naringin and crystal structure of enzyme 2VF5: PDB.