Antimicrobial activity of essential oils from introduced varieties of Dracocephalum moldavica and Hyssopus officinalis

Abstract

Background: Aromatic and medicinal plants are highly valued for their potential influence on functional food systems due to their content of bioactive compounds and health-promoting properties. These plants have antimicrobial and antioxidant effects. Dracocephalum moldavica and Hyssopus officinalis essential oils have notable biological activity among aromatic and medicinal plants. As the demand for natural, plant-based alternatives to synthetic food preservatives has grown, these species have gained attention for their applications as functional foods. This study investigates the antimicrobial properties of their essential oils to evaluate their potential as natural, health-enhancing ingredients in functional foods.

Objective: This research aimed to evaluate the antimicrobial activity of essential oils extracted from Dracocephalum moldavica and Hyssopus officinalis while cultivating such plants under Armenian conditions. Furthermore,  their potential as natural antimicrobial agents in functional food systems was assessed.  

Methods: This study involved three varieties of Dracocephalum moldavica (Moldavia, Gorynych, and Ametist) and three varieties of Hyssopus officinalis (Accord, Inej, and Lazur). Essential oils were extracted through hydro-distillation. Their antibacterial properties were evaluated against five key sanitary indicator microorganisms: Staphylococcus aureus, Salmonella enterica, Bacillus subtilis, Clostridium perfringens, and Escherichia coli Hfr H. The antimicrobial activity was determined using the agar disk diffusion method, by which the inhibition zones around the oil-treated disks were measured.

Results: The essential oil Dracocephalum moldavica consistently demonstrated more substantial antimicrobial effects than Hyssopus officinalis. This was observed across all tested microorganisms and at both concentrations (5% and 0.5%). At 5%, the least effective D. moldavica variety (Ametist) produced inhibition zones between 18.1 mm (E. coli) and 33.0 mm (B. subtilis). The most active H. officinalis variety (Inej) ranged from 16.2 mm to 21.0 mm. Notably, D. moldavica (Gorynych) showed a significant effect against S. aureus with a 41.2 mm inhibition zone, nearly double the distance measured for H. officinalis (Accord: 18.3 mm). At 0.5%, D. moldavica oils maintained high activity (up to 36.0 mm), while H. officinalis rarely exceeded 16.7 mm. Both oils were effective against gram-positive bacteria, yet D. moldavica was more beneficial. 

Novelty: This study uniquely compares the antimicrobial properties of essential oils derived from varieties of Dracocephalum moldavica and Hyssopus officinalis cultivated under Armenian conditions. The findings revealed that D. moldavica oils exhibit stronger and more consistent antimicrobial effects, especially against gram-positive bacteria, highlighting their promising application as natural preservatives in functional food systems.

Conclusion: The pronounced antimicrobial activity of essential oils from D. moldavica varieties, especially Gorynych, accentuates their potential to be used as natural preservatives. Their effectiveness at low concentrations ensures cost-efficiency and a lower likelihood of undesirable side effects. In contrast, while H. officinalis essential oils show more moderate activity; they may hold value in applications that prefer gentler antimicrobial action. 

Keywords: Moldavian dragonhead, hyssop, Staphylococcus aureus, Salmonella enterica, Bacillus subtilis, Clostridium perfringens, Escherichia coli Hfr H.