Evaluation of the antimicrobial and antifungal effect of nano-emulsions loaded by oil extract of Thymus kotschyanus
Evaluation of the antimicrobial and antifungal effect of nano-emulsions loaded by oil extract of Thymus kotschyanus
Zahra khodaverdi,1,*Maryam Hassan,2Somayeh Sadighian,3
1. Zanjan Pharmaceutical Biotechnology Research Center, Zanjan University of Medical Sciences, Zanjan, I.R. Iran 2. Zanjan Pharmaceutical Biotechnology Research Center, Zanjan University of Medical Sciences, Zanjan, I.R. Iran 3. Department of Pharmaceutical Biomaterials, School of Pharmacy, Zanjan University of Medical Sciences, Zanjan, Iran
Introduction: The development of antibiotics has been a major breakthrough in medical world as a powerful means of curing diseases and preventing infections. However, in recent years, antimicrobial resistance has become one of the most significant medical concerns. Therefore, to tackle this issue alternative options such as implementing herbal oil extract as an antibacterial agent have to be taken into consideration. Nevertheless, the volatility, poor water solubility, as well as sensitivity to light and oxygen, are the main drawbacks of using essential oils. Therefore, nanoencapsulation of essential oil (EO) which was successfully used in our study appears to be a great way to enhance physiochemical attributes namely bioavailability, solubilization, and thermal stability.
Methods: In this study, the EO of Thymus kotschyanus which is a medicinal herb belonging to the Lamiaceae family was extracted by hydro-distillation method Clevenger type and the components of EO were analyzed by gas chromatography –mass spectrometry (GC-MS). Then, the EO was loaded into a nano-emulsion mainly made of Twin 80 and Span 60 as surfactants. It was synthesized by a high-pressure homogenizer and the thermal stability of particles was investigated at three (4, 25 and 40 C) temperatures for 84 days. Moreover, morphology of the nanoemulsions was evaluated by Transmission Electron Microscope (TEM) and Atomic Force Microscopy (AFM). The release of the EO from the nano-emulsion was investigated for 24 hours. Ultimately, the antimicrobial and antifungal impact of nano-emulsion was investigated by both micro-broth and macro-broth dilution tests against 6 species of gram-negative bacteria, 6 species of gram-positive bacteria, Aspergillus niger, and Candida albicans.
Results: Analysis of morphological characterization by AFM and TEM represented the spherical shape of nanoparticles. The outcome of measurements done by Nano Zetasizer reported an average size of 135 nanometers and revealed a regular distribution of nanoparticles. Furthermore, in the in-vitro drug release test, more than 55 percent of the loaded EO was released in the first 5 hours and the rest of the EO was secreted steadily until the end of the assessment. The inhibitory effect of EO and Nano emulsion containing essential oil (NEO) is more than antibiotics on gram-negative bacteria such as Salmonella typhi (MBC and MIC of NEO = 1/56×10-2 / MBC of antibiotic = 6/25×10-2) and also their effect is remarkable on gram-positive bacteria like Bacillus subtilis (MBC and MIC of NEO = 4×10-4 / MBC of antibiotic = 7×10-4). However, no progress was seen in inhibiting the growth of Pseudomonas aeruginosa in various concentrations by neither the EO nor the NEO. In addition, both EO and NEO caused inhibition in the growth of Candida albicans and Aspergillus niger. Moreover, prior to all antibacterial tests the effect of the EO in inhibiting the growth of microorganisms was also assessed by measuring the diameter of inhibitory zone. Bacillus subtilis with inhibitory zone of 36 mm was the most susceptible bacteria.
Conclusion: According to the reports of current research, the nano-emulsion of Thymus kotschyanus has a noticeable antimicrobial and antifungal effect and can be a priceless source for curing diseases specially in case of multi drug antimicrobial resistance. Since in preparation of the nano-emulsion less oil extract is used, it can be assumed that the encapsulated EO represents higher efficacy in comparison with pure EO specifically in gram-negative bacteria. What is more, due to the accessibility of Thymus kotschyanus and feasible process of synthesizing the nano-emulsion, application of this nano herbal drug is highly recommended.