Natural Defence Potential of Syzygium aromaticum Oil Against Microbial and Fungal Pathogens

Abstract

The increasing prevalence of antimicrobial resistance (AMR) among pathogenic microorganisms poses a serious threat to global public health and necessitates the development of effective alternative antimicrobial agents. Plant-derived essential oils have emerged as promising candidates due to their broad-spectrum activity and multi-target mechanisms of action. The present study evaluated the antibacterial and antifungal potential of Syzygium aromaticum (clove) essential oil against selected pathogenic microorganisms. Clove oil was extracted from dried flower buds by hydro-distillation and tested against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis), Gram-negative bacteria (Escherichia coli, Salmonella typhi), and pathogenic fungi (Candida albicans and Aspergillus niger). Antimicrobial activity was assessed using agar well diffusion and broth microdilution methods, following Clinical and Laboratory Standards Institute guidelines. The essential oil exhibited significant, concentration-dependent antibacterial and antifungal activity, with greater efficacy against Gram-positive bacteria. Staphylococcus aureus showed the highest susceptibility, with a minimum inhibitory concentration (MIC) of 0.125 mg/mL, whereas E. coli displayed comparatively higher resistance (MIC: 0.25 mg/mL). Pronounced antifungal activity was observed against Candida albicans. The antimicrobial efficacy of clove oil is attributed primarily to its high phenolic content, particularly eugenol, which disrupts microbial membrane integrity, increases permeability, and interferes with key metabolic processes. The multi-target mode of action reduces the likelihood of resistance development. These findings support the potential application of Syzygium aromaticum essential oil as a natural antimicrobial agent in pharmaceutical, food preservation, and cosmetic formulations, warranting further in vivo and toxicological investigations.

Introduction

The rise of antimicrobial resistance (AMR) poses a global health threat, reducing the effectiveness of conventional antibiotics and antifungals. This has led to increased interest in natural alternatives, particularly plant-derived essential oils, which have broad-spectrum antimicrobial activity and a lower risk of resistance due to multi-target mechanisms.

Syzygium aromaticum (clove) essential oil, rich in eugenol (70–85%), has traditional uses as an analgesic, antiseptic, anti-inflammatory, and antimicrobial agent. Studies show it is effective against both Gram-positive and Gram-negative bacteria (e.g., Staphylococcus aureus, Escherichia coli, Salmonella typhi) and fungi (e.g., Candida albicans, Aspergillus niger). Its antibacterial action disrupts cytoplasmic membranes, increasing permeability and causing leakage of cellular contents, while antifungal activity involves interference with ergosterol synthesis and membrane destabilization.

In laboratory tests, clove oil demonstrated dose-dependent antibacterial and antifungal activity, with lower MIC values against Gram-positive bacteria like S. aureus compared to Gram-negative strains. Its multi-target action reduces the likelihood of resistance development, making clove essential oil a promising natural antimicrobial alternative for pharmaceutical, food, and cosmetic applications.

Conclusion

The present study demonstrates that Syzygium aromaticum essential oil possesses significant antibacterial and antifungal activities against selected pathogenic microorganisms. The oil exhibited a clear concentration-dependent inhibitory effect against both Gram-positive and Gram-negative bacteria, with Staphylococcus aureus showing greater susceptibility than Escherichia coli, as evidenced by larger zones of inhibition and lower MIC values. This differential sensitivity can be attributed to structural differences in bacterial cell envelopes, particularly the protective outer membrane present in Gram-negative bacteria. In addition to its antibacterial efficacy, clove essential oil showed pronounced antifungal activity against Candida albicans, supporting its potential use against opportunistic fungal infections. The strong antimicrobial performance of clove oil is largely attributed to its high phenolic content, especially eugenol, which exerts its effect through multiple mechanisms including disruption of cell membrane integrity, increased membrane permeability, leakage of intracellular components, inhibition of key metabolic enzymes, and interference with ergosterol biosynthesis in fungi. The multi-target mode of action of clove essential oil is particularly advantageous, as it reduces the likelihood of resistance development compared to conventional synthetic antimicrobial agents. These findings reinforce the growing interest in plant-derived essential oils as effective and sustainable alternatives to synthetic antibiotics and antifungals. Overall, the results of this investigation provide scientific evidence supporting the potential application of Syzygium aromaticum essential oil as a natural antimicrobial agent in pharmaceutical formulations, food preservation systems, and cosmetic products. However, further studies focusing on toxicity evaluation, formulation optimization, and in vivo efficacy are necessary to fully validate its safety and clinical applicability.

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Copyright

Copyright © 2025 Salam Harun Nadaf. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.