Cell and Tissue Journal

Abstract Introduction: Plant-derived exosome-like nanoparticles (PDENs) are nano-sized vesicles released by plant cells. They contain a lipid bilayer membrane and carry bioactive molecules such as proteins, lipids, nucleic acids, and secondary metabolites. Due to their low toxicity and natural drug delivery potential, they have gained attention for therapeutic applications. Plant extracts are also rich in phenolic compounds and flavonoids with known antioxidant and antimicrobial effects. The rising problem of antibiotic resistance in pathogens like Escherichia coli, Staphylococcus aureus, and Streptococcus pyogenes has created an urgent need for new natural agents.
Aim: This study aimed to isolate and characterize exosomes from ginger, lavender, onion, and lemon, and to compare their antioxidant and antibacterial activities with those of aqueous extracts from the same plants.
Materials and methods: Fresh ginger, lavender, onion, and lemon were used for the preparation of plant extracts and exosome isolation. For aqueous extraction, 2 g of ginger and lavender samples were homogenized with 20 mL of distilled water and incubated in a water bath at 70°C for 90 minutes. The mixtures were centrifuged at 3000 × g for 10 minutes, and the supernatants were filtered and stored at 4°C until analysis. Exosomes were isolated using the Exosun Exosome Isolation Kit (EXOSUN Company). Plant materials were homogenized, filtered, and subjected to differential centrifugation. The resulting supernatants were processed according to the manufacturer's instructions using buffers A and B. Due to the acidic nature of lemon juice, modification of the protocol was required by increasing the concentration of buffer A to facilitate exosome precipitation. Protein concentration of isolated exosomes was determined using the Bradford assay with bovine serum albumin (BSA) as the standard. Exosome morphology was characterized by transmission electron microscopy (TEM). The antioxidant activity of extracts and exosomes was evaluated using the Ferric Reducing Antioxidant Power (FRAP) assay. Samples were analyzed in 96-well microplates, and absorbance was measured at 570 nm. Antibacterial activity was assessed against Escherichia coli, Staphylococcus aureus, and Streptococcus pyogenes using the disk diffusion method. Sterile blank disks were impregnated with plant extracts or exosome preparations at concentrations of 25, 50, and 100 mg/mL and placed on Mueller-Hinton agar plates inoculated with bacterial suspensions adjusted to a 0.5 McFarland standard. Gentamicin and vancomycin served as positive controls. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were determined using the broth microdilution method in 96-well microplates. All experiments were performed in triplicate. Statistical analyses were conducted using SPSS version 27, applying one-way ANOVA followed by Tukey’s post hoc test, with p <0.05 considered statistically significant.
Results: TEM confirmed successful isolation of exosome-like vesicles from all plants. Bradford assay indicated protein-containing nanoparticles. FRAP analysis showed that lavender had the highest antioxidant capacity. Plant extracts generally showed greater antioxidant activity than their corresponding exosomes. Antibacterial testing revealed that exosomes from all four plants had no detectable antibacterial effect. Similarly, aqueous extracts of ginger, lavender, and onion showed no inhibition. However, lemon extract exhibited significant antibacterial activity against all three bacteria. MIC values of lemon extract were 3.12 mg/mL for S. aureus, 6.25 mg/mL for S. pyogenes, and 50 mg/mL for E. coli. Inhibition zones for S. aureus reached 22 mm at 100 mg/mL. Gram-positive bacteria were more susceptible than Gram-negative E. coli.
Discussion:The spread of antibiotic-resistant pathogens has increased the need for new treatments. In this study, exosomes isolated from ginger, lavender, onion, and lemon showed no antibacterial activity, while among aqueous extracts, only lemon extract displayed good antibacterial properties. The lack of activity in aqueous lavender extract compared to alcoholic extracts in previous reports may be due to solvent differences affecting phenolic compound extraction. Aqueous ginger extract also showed no effect, which contrasts with some alcoholic extracts. However, lavender exosomes demonstrated the highest antioxidant capacity among all samples, highlighting their potential for antioxidant applications.
Conclusion: Although plant-derived exosomes from these four species did not show antibacterial effects under the tested conditions, lemon aqueous extract exhibited promising antimicrobial activity, especially against Gram-positive bacteria. Lavender exosomes showed the strongest antioxidant potential. These findings suggest that lemon extract could serve as a natural antibacterial agent, while lavender-derived exosomes and extracts may be valuable sources of natural antioxidants. Further in vivo studies are needed to explore their efficacy and safety.