Rosemary essential oil: chemical composition, antiviral, cytotoxicity, and in silico molecular docking analysis against tobacco mosaic virus

Abstract

Aromatic plants represent a significant source of bioactive compounds and have recently expanded their potential applications in agriculture. In the current study, the essential oil of Salvia rosmarinus (rosemary) was extracted, and its chemical composition was analyzed using gas chromatography-mass spectrometry (GC-MS). Under greenhouse conditions, the antiviral effectiveness of the essential oil against tobacco mosaic virus (TMV) was evaluated on Nicotiana glutinosa, marking the first comprehensive assessment of its impact on plant viruses. A computational analysis of molecular docking interactions was performed to explore the potential interactions of target compounds with the three protein components of TMV. Additionally, the influence of essential oil on the root tips of Allium cepa was assessed for its genotoxic effects. In comparison to untreated infected plants, the curative treatment demonstrated a peak viral inhibition rate of 76.3% at 300 µg/mL, while the protective and inactivation treatments reached maximum rates of 70.7% and 62.8%, respectively, at the same concentration. At elevated concentrations of essential oil (300 µg/mL), the genotoxicity assay showed a concentration-dependent decrease in the mitotic index and an increase in chromosomal abnormalities. The GC-MS analysis revealed that the primary constituents of the essential oil were α-terpineol (19.3%), isoborneol (14.1%), and camphor (13.2%). Furthermore, an in-silico assessment of the candidate phytoconstituents indicated that the antiviral properties are mainly associated with the isoaromadendrene epoxide (0.35%), cubenol (0.22%), epiglobulol (2.06%), caryophyllene (5.73%), and caryophyllene oxide (2.66%) compounds. Thus, we assert that the synergistic properties of oil components account for their significant antiviral efficacy. Overall, the results of our study suggest that rosemary essential oil demonstrates significant antiviral properties and may serve as a promising antiviral agent for combating plant viral infections. Nonetheless, additional field validation and investigations into individual components and their synergistic combinations are essential to comprehend their effectiveness and maximize their application.

Keywords: Crop protection; Cytotoxicity; GC-MS; Molecular docking; Salvia rosmarinus; Tobacco mosaic virus.

Fig. 1

Photograph illustrating disease symptoms on Nicotiana glutinosa leaves infected with TMV at 5 dpi, demonstrating rosemary essential oil’s protective, curative, and inactivating effects at 200 µg/mL.

Fig. 2

Impact of rosemary essential oil on accumulation level (A) and inhibition percent (B) of TMV upon protective, curative, and inactivation treatments at different concentrations. Each column represents the mean of three replicates. Group differences were assessed using a one-way analysis of variance (ANOVA) and Tukey’s HSD test at the p ≤ 0.05 significance threshold within the CoStat statistical software. Statistical significance was denoted alphabetically above the histogram in ascending order: a > b > c > d.

Fig. 3

GC-MS chromatogram of rosemary essential oil extract. Compounds numbered 1 to 6 represent the top six compounds that interacted with TMV proteins based on the analysis of molecular docking interactions.

Fig. 4

Illustration of the three-dimensional molecular docking interactions that occur between isoaromadendrene epoxideto and TMV-replicase large subunit protein (A), epiglobulol and TMV-movement protein (B), and isoaromadendrene epoxideto and TMV-coat protein (C).

Fig. 5

Onion root tip cell abnormalities after exposure to 300 µg/mL of rosemary oil. Arrows refer to polyploidy in anaphase (A); chromosomal bridges (B); multinucleated cells (C); star metaphase (D); chromosomal bridge, sticky and breakage (E); c-metaphase (F); aberrations in metaphase (G); Anaphase (H).

Fig. 6

Proposed antiviral actions of rosemary essential oil against tobacco mosaic virus (TMV). This figure illustrates the proposed pathways by which rosemary essential oil inhibits TMV infection, derived from protective, curative, and inactivation assays, as well as in silico molecular docking analysis. The protective pathway indicates that viral entry can be inhibited via a physical barrier or through modulation of host cells. The curative pathway, exhibiting the greatest efficacy, entails the inhibition of two critical intracellular processes: viral replication and viral movement. The inactivation pathway indicates a direct virucidal effect, wherein compounds compromise the integrity of the TMV coat protein. These mechanisms collectively result in a notable decrease in viral load and disease symptoms in Nicotiana glutinosa.