Summary: New laboratory research suggests some essential oils can improve mood and reduce anxiety and depression symptoms by producing antioxidant effects in the brain.
Source: Monash University
Monash University scientists have identified mechanisms that help explain why certain essential oils benefit mood.
Their results appear in the journal Neurochemistry International.
Essential oils (EOs) are mixtures of volatile plant compounds commonly used in aromatherapy. Because they evaporate at room temperature, inhaled EOs can enter the bloodstream and reach the brain, producing effects that differ from dietary plant compounds taken by mouth.
Although aromatherapy has long been associated with improvements in emotional wellbeing, the field has lacked a clear framework to determine which oils, at what concentrations, and under what conditions are most likely to deliver therapeutic benefit. This study addresses that gap by linking the chemical behavior of oils with their likely effects on brain oxidative chemistry.
“Aromatherapy under particular conditions is reported to consistently enhance emotional health, including lowering anxiety and depression,” said Professor Louise Bennett from the Monash University School of Chemistry, lead author of the study. “However, achieving benefits requires understanding which types are best and what dose is required.”
The researchers focused on interactions between EOs and ascorbate (vitamin C), which exists at high concentrations in the brain and can act as a signaling molecule and regulator of oxidative stress. Their experiments show that ascorbate can produce hydrogen peroxide (H2O2) under physiological conditions, but that certain essential oils suppress this production (acting as antioxidants) while others enhance it (acting as pro-oxidants).
Lavender oil, for example, was found to have strong antioxidant properties in the experimental system, consistent with many clinical reports that lavender improves mood and reduces anxiety. The team proposes that those antioxidant effects—specifically the suppression of ascorbate-driven H2O2 formation—are likely to underlie lavender’s anxiolytic benefits.
By systematically testing single oils and combinations with ascorbate, the researchers discovered that some EOs reduce H2O2 production (antioxidant effect), while others increase it (pro-oxidant effect). Importantly, the net outcome depends on the concentration ratios within mixtures: an oil that is antioxidant in one context may not behave the same way when combined with other components. In more complex three-component mixtures the intrinsic pro-oxidant chemistry of ascorbate often dominates, changing the overall balance.
Ph.D. candidate Minoli Aponso, a co-author on the paper, explained the chemical model the team developed. Certain compounds can donate electrons and thereby regenerate oxidized forms of ascorbate, driving continued H2O2 production and producing a net pro-oxidant effect. Other compounds react irreversibly with oxidized ascorbate intermediates, suppressing H2O2 formation and producing a net antioxidant effect.
This mechanistic clarity allows researchers to classify EOs by their likely influence on brain oxidative chemistry and thus to better predict therapeutic outcomes. Oils that promote antioxidant activity in the brain may be useful for mood regulation and anxiety relief, while oils that promote pro-oxidant activity may be better suited for applications such as antimicrobial or anticancer strategies.
“For the first time, this work paves the way to select and classify EOs according to their mechanistic properties and to potentially develop inexpensive but effective therapies for the brain,” Professor Bennett said. She and Aponso are exploring the development of EO-based applications for mood disorders, infection control, inflammation, and possibly cancer, while also refining methods to predict inhalable doses under different temperatures and climates.
Understanding safe and effective dosing is a key part of translating these findings. The research team reports they can predict the volatile, inhalable dose of any essential oil across a range of temperatures, a step that could help standardize aromatherapy practice and improve reproducibility in future clinical studies.
About this psychology research news
Author: Press Office
Source: Monash University
Contact: Press Office – Monash University
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Original Research: Closed access.
“Anxiolytic effects of essential oils may involve anti-oxidant regulation of the pro-oxidant effects of ascorbic acid in the brain” by Minoli Aponso et al., Neurochemistry International
Abstract
Anxiolytic effects of essential oils may involve anti-oxidant regulation of the pro-oxidant effects of ascorbic acid in the brain
Essential oils absorbed through inhalation are frequently reported to produce anxiolytic effects, but the underlying neurochemical mechanisms have been unclear. The brain contains relatively high concentrations of ascorbate (approximately 10 mM in neurons), which can act as both a signaling molecule and a regulator of oxidative stress.
In laboratory experiments, ascorbate produced measurable H2O2 in the presence of oxygen at physiological pH, with peak H2O2 concentrations observed around certain ascorbate levels. Individual essential oils and selected neurotransmitters produced lower levels of H2O2 when tested at comparable concentrations.
Systematic testing of binary and ternary mixtures containing ascorbate revealed that essential oils and neurotransmitters can either enhance (pro-oxidant, POX) or suppress (antioxidant, AOX) H2O2 production relative to ascorbate alone, depending on concentration ratios. Effects observed in simple mixtures did not always predict outcomes in more complex mixtures, where ascorbate-driven pro-oxidant chemistry frequently prevailed.
The authors propose a model in which electron-donating compounds catalytically regenerate ascorbate from its oxidized intermediates, driving H2O2 formation and producing a net pro-oxidant effect. Conversely, compounds that irreversibly react with oxidized ascorbate intermediates suppress H2O2 formation and yield an overall antioxidant effect.
Because anxiolytic effects of certain EOs, including extracts of Lavandula angustifolia (lavender) and Salvia rosmarinus (rosemary), were associated with antioxidant regulation of ascorbate-driven H2O2 production, these mood benefits may be linked to their AOX properties. By contrast, EOs that promote pro-oxidant chemistry (for example, Juniper berry oil) may be better suited for antimicrobial or cytotoxic applications.