The effect of different radiation intensities on the oil yield and main quality of stems and leaves of Cymbopogon citratus (DC.) Stapf

Lemongrass (Cymbopogon citratus (DC.) Stapf), as an important medicinal and aromatic plant, has been widely used in food and pharmaceutical industries owing to its essential oil. However, traditional extraction methods using whole plants for lemongrass oil production are associated with challenges such as inconsistent oil quality and poor stability. To clarify the impacts of cultivation environments and plant parts on oil quality, this study assigned lemongrass plants to shaded and natural light exposure groups. Essential oils were extracted from leaves and stems using steam distillation, followed by compositional analysis using Headspace Solid-Phase Microextraction (HS-SPME) and Gas Chromatography–Mass Spectrometry (GC–MS). The investigation focused on how different radiation intensities affect physicochemical properties and volatile components of essential oils from various plant parts. Results demonstrated that both physicochemical properties and volatile compositions of lemongrass essential oils exhibited low sensitivity to variations in radiation intensity treatments. The oil yield of lemongrass leaf essential oil was significantly higher than that of stem oil by 54.48%, but the refractive index and chromatic aberration of the two showed no significant differences. The contents of heterocyclic compounds, ethers, and aldehydes in leaf essential oil were significantly higher than those in stem oil by 14.61%, 10.83%, and 1.57%, respectively, while hydrocarbons were lower by 6.1%. Geraniol and citral, as the main volatile components characterizing the quality of lemongrass, Geraniol and 2,6-Octadienal, 3,7-dimethyl-, (E)- were found to be significantly higher in the leaves than in the stems by 8.64% and 7.20%, respectively (P<0.01). Therefore, lemongrass essential oil extracted from leaves cultivated under natural light conditions demonstrated the highest oil yield and optimal quality parameters. The implementation of natural light cultivation combined with targeted leaf harvesting proposes a promising approach to enhance lemongrass oil quality. This methodology provides a theoretical foundation for advancing deep processing techniques and developing high-value products derived from lemongrass essential oil.