Anti‐Inflammatory Activity of Essential Oils: A PRISMA 2020‐Compliant Systematic Review of 46 Preclinical Studies (In Vitro and In Vivo)

ABSTRACT

Chronic inflammation is involved in the majority of non‐communicable diseases, and although conventional anti‐inflammatory drugs have demonstrated their effectiveness, their side effects encourage the search for natural therapeutic alternatives. In this context, essential oils (EO) represent a promising source of bioactive molecules. This systematic review, conducted according to the PRISMA 2020 guidelines, aims to synthesize the available preclinical data concerning the anti‐inflammatory properties of medicinal plant essential oils, while assessing the methodological quality of the studies and exploring potential interactions between chemical composition and biological activity. A literature search was conducted in PubMed/MEDLINE, Google Scholar and ScienceDirect for the period 2014–2025. Only studies reporting a chromatographic analysis by GC–MS as well as a quantitative measurement of at least one inflammatory marker (COX‐2, LOX, NO, cytokines or in vivo edema) were retained. Among the 170 references identified, 46 studies met the inclusion criteria. The results show a predominance of the Lamiaceae family (29.9%), mainly represented by the genera Thymus, Origanum and Lavandula. The most frequently reported major compounds were carvacrol, β‐caryophyllene and α‐pinene, followed by 1,8‐cineole and linalool. Inhibition of 5‐LOX was the most frequently assessed biological target. The lowest IC ₅₀ values for this target were reported for Origanum compactum (0.68 μg/mL) and Eucalyptus globulus (0.88 μg/mL). Concerning COX‐2, an IC ₅₀ value of 1.51 μg/mL associated with a selectivity index of 5.56 was reported for Ammoides verticillata. In vivo models of carrageenan‐induced edema, inhibition rates of 98.36%, 92.42% and 89.99% were observed for Cedrus atlantica, Duguetia furfuracea and a synergistic Thymus algeriensis/ Artemisia herba‐alba mixture, respectively. The analysis of the included studies also highlights significant methodological heterogeneity regarding the tested doses, the positive controls used, and the experimental models employed, limiting the comparability of the results. The low frequency of simultaneous evaluations of multiple inflammatory targets (COX‐2, LOX and cellular mediators) as well as the absence of formalized correlations between chemical composition and biological activity constitute the main gaps identified in the available literature.