Toxicological Assessment of Origanum majorana L.: Evaluation of Its Cytotoxicity, Genotoxicity, and Acute Oral Toxicity

TL;DR

This study evaluates the safety of Origanum majorana, finding it generally safe but with potential DNA-damaging effects at high doses.

Contribution

The study provides the first comprehensive in vitro and in vivo toxicological assessment of Origanum majorana extract.

Findings

The extract showed no cytotoxicity but induced dose-dependent DNA damage in vitro.

In vivo, it was safe at high doses with no mortality and showed hepatoprotective effects.

Histopathological changes were mild and likely adaptive, not irreversible.

Abstract

Medicinal plants remain central to traditional healthcare, yet their increasing integration into modern pharmacology necessitates robust toxicological evaluation. Origanum majorana L. (sweet marjoram), widely used in culinary and folk medicine, contains diverse secondary metabolites with both therapeutic and potential genotoxic activities. Despite its popularity, systematic in vivo and in vitro safety assessments remain limited. This study aimed to comprehensively evaluate the acute oral toxicity, cytotoxicity, and genotoxicity of O. majorana methanolic extract, providing baseline toxicological data to support its safe traditional use and potential pharmaceutical applications. The methanol extract of O. majorana leaves was tested in NIH-3T3 fibroblasts for cytotoxicity and genotoxicity. In vivo acute oral toxicity was assessed in rats according to OECD Guideline 420, with animals monitored over 14 days for clinical signs, hematological and biochemical alterations, and histopathological changes. The extract preserved fibroblast viability above 90% across all tested concentrations (10–200 µg/mL), indicating absence of cytotoxicity. However, comet and micronucleus assays revealed dose-dependent DNA damage, suggesting genotoxic potential at higher exposures. In vivo, no mortality or overt systemic toxicity was observed at doses up to 2000 mg/kg. Hematological analyses showed immunomodulatory shifts (increased neutrophils and monocytes, reduced eosinophils), while biochemical profiles indicated hepatoprotective and cardioprotective effects, with reduced ALT, AST, and LDH levels. Histopathological evaluation revealed only mild, focal changes consistent with adaptive rather than irreversible responses. O. majorana extract demonstrates a favorable acute safety profile with preserved hepatic and renal function, hematological modulation, and absence of in vitro cytotoxicity. Nevertheless, dose-dependent genotoxicity warrants caution for concentrated formulations. According to GHS classification, the extract aligns with Category 5 (acute oral toxicity, lowest hazard) and Category 2 (germ cell mutagenicity). These findings underscore the importance of dose management and further long-term genotoxicity studies before translational applications in nutraceutical or biomedical fields.

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