Comprehensive chemical profiling of citrus peel essential oils by direct‑infusion ultrahigh‑resolution FT‑ICR MS and high‑resolution GC–QTOF MS

Abstract

Citrus fruit peels constitute an abundant yet underutilized source of agricultural waste, despite being rich in bioactive compounds with potential applications in cosmetics, food products, biodegradable pesticides, and various techno-chemical industries. In this study, essential oils were extracted from the peels of grapefruit, lemon, lime, mandarin, and orange, and their chemical compositions were analyzed using direct‑infusion (DI) ultrahigh‑resolution Fourier transform ion cyclotron resonance (FT‑ICR) mass spectrometry and high‑resolution gas chromatography–quadrupole time‑of‑flight (GC–QTOF) mass spectrometry. By combining these two techniques, the study offers comprehensive insights into the complex chemistry of citrus peel essential oils, laying the foundation for their broader application. DI FT-ICR MS detected up to 2,300 spectral features (chemical compounds) in the samples, of which 228 were tentatively identified. These included terpenes and terpenoids, carotenoids, fatty acids, phenolic acids, flavonoids, and esters. Notably, over 100 of these compounds have not been previously reported in citrus peel essential oils or other citrus-derived products. In addition, high-resolution GC-QTOF MS identified 38 volatile compounds, including different terpene isomers that were not resolved by DI FT-ICR MS, thereby complementing the analysis. These findings suggest that citrus peel essential oils are significantly more chemically diverse than previously anticipated. • The chemical compositions of five citrus peel essential oils were determined • Two complementary mass spectrometric techniques were used • More than 100 novel compounds were tentatively identified • Heatmaps illustrated similarities and differences between the peel oils

Topics & Concepts