Biological activities (antimicrobial, anti-inflammatory, anti-coronavirus (229E)) and chemical composition of some essential oils

Why everyday oils matter for modern health

As germs grow increasingly resistant to antibiotics and new viruses continue to emerge, scientists are searching for safe, affordable ways to protect people and preserve food. This study explores four familiar plant-based essential oils—menthol, lemon, clove and camphor—to see how well they can slow the growth of harmful microbes, calm inflammation in the body and weaken a common human coronavirus, all while identifying which natural ingredients inside these oils are most responsible for their effects.

Plant scents put to the test

The researchers focused on essential oils that are already widely used in households, traditional remedies and commercial products. They worked with oils from mint (menthol), lemon, clove and camphor trees, and challenged them with a panel of troublemaking microbes: several disease-causing bacteria, a yeast and a mold that commonly spoils food. Instead of testing the oils in people, they used standard laboratory plates where microbes are spread on a gel and the oils are added to small wells. If an oil is effective, it creates a clear circle where microbes cannot grow. All four oils produced such clear zones, showing broad antimicrobial power, but menthol and camphor stood out by creating the largest areas of no growth, especially against the food-spoilage mold Aspergillus niger and the hospital-linked bacterium Pseudomonas aeruginosa.

Calming the body’s fire

Because long-lasting inflammation underlies many chronic illnesses, the team next asked whether these oils could help cool an exaggerated inflammatory response. They used a simple model in which a blood protein is heated so that it begins to unravel—a process that can trigger immune reactions in the body. When mixed with the oils before heating, this protein was better protected. Menthol was by far the most effective at blocking this damage, cutting it by nearly two-thirds, while camphor and lemon showed modest effects and clove trailed behind. Although this is an early laboratory test rather than a clinical trial, it suggests that some essential oils may help stabilize proteins and influence the body’s inflammatory signaling rather than simply masking symptoms with scent.

Challenging a common coronavirus

To probe antiviral potential, the scientists turned to a well-studied human coronavirus called 229E, which causes colds and is handled under lower safety conditions than pandemic strains. They grew mammalian cells in dishes, exposed them to the virus and then added different doses of each essential oil. By observing how well the cells survived and how much viral damage was prevented, they could estimate how much oil was needed to halve viral activity, and how toxic that same oil was to the cells themselves. Lemon oil was the strongest at stopping the virus but was also the harshest on cells, giving it the narrowest safety window. Camphor oil, while less potent against the virus, was much kinder to host cells, earning the best overall safety margin. Clove and menthol fell in between these two extremes. Together, the patterns suggest that these everyday oils can interfere with viral entry or stability, but must be carefully balanced to avoid harming healthy tissue.

What’s inside the bottle

To understand which natural ingredients might drive these effects, the team chemically profiled the menthol and camphor oils using a sensitive separation-and-detection method that reveals individual components. Camphor oil was rich in a compound called eucalyptol, along with camphor itself and several related molecules that earlier studies have linked to antibacterial, antifungal, anti-inflammatory and antiviral actions. Menthol oil contained notable amounts of a fatty acid (9,12-octadecadienoic acid) and menthol-related structures, both previously reported to fight microbes and temper inflammation. These fingerprints do not prove which exact molecules are responsible, but they highlight promising candidates for future, more targeted testing.

Natural helpers, not magic cures

Overall, the study shows that common essential oils from mint, lemon, clove and camphor trees can slow a wide range of harmful microbes, modestly reduce a simple measure of inflammation and weaken a human coronavirus in cell culture. Menthol and camphor were the strongest all-round performers, while lemon and clove contributed useful antiviral and antimicrobial properties with different safety trade-offs. For everyday readers, the takeaway is not that these oils are ready-made cures for infections, but that nature’s fragrances contain active ingredients with real biological bite. With careful testing, purification and dosing, such plant-based compounds could support safer disinfectants, food-preserving films or complementary treatments that ease the burden on conventional drugs in our ongoing fight against resistant germs and emerging viruses.

Citation: Gab-Allah, G.E., Abouelwafa, A.E. & Hassan, S.W.M. Biological activities (antimicrobial, anti-inflammatory, anti-coronavirus (229E)) and chemical composition of some essential oils. Sci Rep 16, 13392 (2026). https://doi.org/10.1038/s41598-026-48032-1

Keywords: essential oils, natural antimicrobials, antiviral activity, plant-based remedies, camphor and menthol