GC–MS Analysis of Supercritical CO₂ Lemon Peel Extracts from Limoncello Waste

Turning agro-industrial by-products into useful materials is a sustainable way to reduce waste while creating valuable natural compounds. Spent lemon peels left over from limoncello production in Southern Italy were explored by researchers as a possible source of beneficial substances using supercritical CO₂ extraction. The extracts were then analyzed using gas chromatography–mass spectrometry (GC-MS), which showed a complex mix of natural plant chemicals, mainly made up of monoterpenes and oxygenated monoterpenes. A paper based on their research was published in the journal Analyst.¹

What Makes Citrus Fruits and their Processing Waste Valuable?

Citrus fruits (from the Citrus genus in the Rutaceae family), often called “agrumes,” are among the most widely grown fruit crops in the world and are an important part of many diets globally. They are well known for being rich in vitamin C and contain several B vitamins, including thiamine, niacin, riboflavin, pyridoxine, pantothenic acid, and folate. In addition, they provide a range of natural plant compounds such as carotenoids, flavonoids, and limonoids, which contribute to their nutritional value.² Furthermore, citrus processing generates large quantities of agricultural by-products, which can be valuable sources of bioactive compounds and essential oils.³

The food processing industry generates large amounts of organic waste, which is often sent to landfills or burned, causing both environmental harm and economic loss. In many cases, by-products from food production—such as peels, seeds, stems, wastewater, and pulp—can make up more than 40% of the total plant material. This is especially true for foods like citrus fruits, papaya, pineapple, and asparagus.⁴ Among the most promising sources of raw material are citrus by-products, especially lemon peels, which are widely available, inexpensive, and rich in useful natural plant compounds.⁵

Do Lemon Peel Extracts Show Safety and Beneficial Effects for Skin Use?

Two plant extracts (EO-A and EO-B) were chosen based on how well they were obtained, their chemical makeup, and safety. Tests on skin cells showed they were very gentle, with over 90% of cells remaining healthy even at higher doses. Both extracts also showed strong antioxidant effects, especially EO-B, meaning they can help protect against damage caused by free radicals. In addition, they were able to inhibit the growth of several bacteria, including Salmonella typhi and Escherichia coli. They also showed signs of supporting skin health by slowing down enzymes linked to skin aging, reducing processes involved in dark spot formation, and acting against acne-related bacteria. Early human testing suggested benefits such as improved skin hydration, softness, and elasticity.¹

“Overall,” write the authors of the paper,¹ “these findings support the use of supercritical CO₂ extraction as a green, sustainable, and highly efficient technology, coupled with a well-established and widely recognized analytical technique, for converting lemon peel waste into multifunctional and eco-sustainable cosmetic ingredients.”

The researchers believe that more research is needed to understand exactly how lemon essential oils influence skin at a biological level. Future studies should include larger groups of participants and longer testing periods to confirm these early findings and better evaluate their potential use in cosmetic products.¹

Although this study focused on lemon peel waste from limoncello production, the same general approach could potentially be applied to other food and agricultural by-products with similar chemical characteristics. However, more work is needed to see how well this would translate to different materials and industrial conditions, along with proper evaluation of cost, scalability, and supply chain feasibility.¹

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References

1. Di Lorenzo, R.; Neri, I.; Raimondo, R. et al. Upcycling Lemon Peel Waste into Sustainable Bioactive Ingredients: Chemical Characterization and Efficacy Assessment. Analyst 2026. DOI: 10.1039/d6an00048g
2. Barbulova, A.; Colucci, G.; Apone, F. New Trends in Cosmetics: By-Products of Plant Origin and Their Potential Use as Cosmetic Active Ingredients. Cosmetics 2015, 2 (2), 82-92. DOI: 10.3390/cosmetics2020082
3. Pavithra, P. S.; Sreevidya, N.; Verma, R. S. Antibacterial Activity and Chemical Composition of Essential Oil of Pamburus missionis. J Ethnopharmacol. 2009, 124 (1), 151-153. DOI: 10.1016/j.jep.2009.04.016
4. Baik, J. S.; Kim, S. S.; Lee, J. A. et al. Chemical Composition and Biological Activities of Essential Oils Extracted from Korean Endemic Citrus Species. J Microbiol Biotechnol. 2008, 18 (1), 74-79. PMID: 18239420.
5. Ahmad, T.; Esposito, F.; Cirillo, T. Valorization of Agro-Food By-Products: Advancing Sustainability and Sustainable Development Goals 2030 Through Functional Compounds Recovery. Food Bioscience 2024, 62, 105194. DOI: 10.1016/j.fbio.2024.105194