Key Points
- Researchers at the University of Messina (Italy) developed and optimized a method using deep eutectic solvents (DES) composed of chloride and urea for MAE to extract oxygen heterocyclic compounds (OHCs) from citrus-scented creams. This is the first study to apply DESs for OHCs extraction from cosmetic samples.
- Using a high-performance liquid chromatography–photo diode array (HPLC–PDA), the study achieved simultaneous separation and quantification of 35 OHCs—including nine coumarins, nineteen furocoumarins, and seven polymethoxyflavones—in under ten minutes. Out of seven creams analyzed, two samples exceeded recommended FC levels, and one sample violated labelling requirements by omitting the mention of “perfume” or “aroma” despite containing high coumarin levels.
- The researchers highlight the potential health risks from frequent use of cold-pressed citrus essential oils in cosmetics and emphasize the need for regulatory monitoring. They plan to investigate other DESs and extraction procedures to improve recovery values and expand their analytical framework.
University of Messina (Italy) researchers used deep eutectic solvents (DESs) to extract oxygen heterocyclic compounds (OHCs) from citrus-scented creams. Their findings and procedures were published in the Journal of Chromatography A (1).
Cosmetics can be applied to the human body for various purposes, including cleaning, perfuming, and protecting. One market in this industry is skin and sun care products, which includes products like creams. Described as semi-solid emulsions consisting of water, oil, emulsifiers, excipients and active ingredients, creams can have therapeutic effects that stem from active substances, such as essential oils (EOs). Being highly appreciated ingredients for meeting product design specifications, citrus EOs are among the most frequently employed due to their aromas.
The olfactory characteristics of citrus EOs are primarily attributed to their volatile fraction, while the non-volatile fraction leads to the creation of the citrus aroma. Minor components of the latter fraction consist of oxygen heterocyclic compounds (OHCs), more commonly known as coumarins (Cs), furocoumarins (FCs), and polymethoxyflavones (PMFs). OHCs are important in organic chemistry, mainly due to their natural abundance and diverse biological functions (2). These molecules are distinctive to each citrus species, thus being critical for quality control, while coumarin is also used as a fixative or fragrance agent in cosmetic, though they can have side effects.
In this study, the researchers aimed to create a workflow for extracting and quantifying OHCs from citrus-scented creams using a DES for microwave-assisted extraction (MAE). With this process, microwave energy is used to heat solvents in contact with a sample to partition analytes from the sample matrix into the solvent (3). A DES made by chloride and urea, at a molar ratio 1:2, and 20 % of water in weight was selected. The sample proved to be complex, with solid-phase extraction (SPE) clean-up being mandatory to obtain an extract devoid of interferents. Finally, a high-performance liquid chromatography–photo diode array (HPLC–PDA) analytical method was used to allow the simultaneous separation and quantification of 35 oxygen heterocyclic compounds in less than 10 minutes.
To the authors’ knowledge, this study is the first to use a DES for OHCs MAE from cosmetic samples. The extraction procedure was developed, optimized, and validated, thus demonstrating the potentials of DESs and MAE in the field. The HPLC–PDA method enabled the simultaneous separation and quantification of nine Cs, nineteen FCs and seven PMFs in less than ten minutes. Seven citrus-scented creams were screened using the method. Of the analyzed samples, two exceeded recommended FC levels. Additionally, one cream did not comply with labelling requirements, since it did not list “perfume” or “aroma” as an ingredient, despite coumarin being present above recommended limits.
With this research, the researchers hope to alert producers and consumers about the risks associated with frequent use of cold-pressed citrus EOs as ingredients in cosmetic products. While this is a preliminary study, the researchers intend to use other DESs and extraction procedures to measure how they can improve recovery values.
References
(1) Cafeo, G.; Ferrara, D.; Schincaglia, A.; et al. Microwave-Assisted Extraction of Oxygen Heterocyclic Compounds from Citrus-Scented Creams Using a Deep Eutectic Solvent and Their Determination by HPLC-PDA. J. Chromatogr. A 2025, 1756, 466085. DOI: 10.1016/j.chroma.2025.466085
(2) Venkatachalam, H.; Kumar, N. V. A. The Oxygen-Containing Fused Heterocyclic Compounds. Heterocycles - Synthesis and Biological Activities; IntechOpen, 2019. DOI: 10.5772/intechopen.88026
(3) Eskilsson, C. S.; Björklund, E. Analytical-Scale Microwave-Assisted Extraction. J. Chromatogr. A 2000, 902 (1), 227–250. DOI: 10.1016/s0021-9673(00)00921-3
