Comparative Evaluation of Essential Oils from Medicinal-Aromatic Plants of Greece: Chemical Composition, Antioxidant Capacity and Antimicrobial Activity against Bacterial Fish Pathogens

Abstract

The administration of antibiotics in aquaculture has raised concern about the impact of their overuse in marine ecosystems, seafood safety and consumers’ health. This “green consumerism” has forced researchers to find new alternatives against fish pathogens. The present study focused on 12 Mediterranean medicinal-aromatic plants as potential antimicrobials and antioxidant agents that could be used in fish aquaculture. In vitro assays showed that the essential oils (EOs) from all studied plants had anti-bacterial and antioxidant properties, with their efficacy being dependent on their chemical composition. More specifically, EOs rich in carvacrol, p-cymene and γ-terpinene exhibited not only the strongest inhibitory activity against the growth of bacterial pathogens (inhibitory concentration: 26–88 μg mL−1), but also the greatest total antioxidant capacity (ABTS: 2591–5879 μmole mL−1; CUPRAC: 931–2733 μmole mL−1). These compounds were mainly found in the EOs from Greek oregano (Origanum vulgare subsp. hirtum), Spanish oregano (Thymbra capitata) and savoury (Satureja thymbra) collected from cultivations in Greece. The specific EOs stand out as promising candidates for the treatment of bacterial diseases and oxidative stress in farmed fish. Further in vivo experiments are needed to fully understand the effects of EO dietary supplementation on fish farming processes.

Carvacrol, Thymol, and Garlic Essential Oil Promote Skin Innate Immunity in Gilthead Seabream (Sparus aurata) Through the Multifactorial Modulation of the Secretory Pathway and Enhancement of Mucus Protective Capacity

“…Functional feeds containing essential oils, one of most commonly used group of phytogenics in aquafeeds, have received increased attention during these last years due to their antimicrobial, immunostimulant, antioxidant, anti-stress, and growth-promoting properties (3)(4)(5). Besides essential oils being repeatedly demonstrated to stimulate both humoral and cellular components of the fish innate immunity (6), numerous have been also shown to display a noteworthy antimicrobial activity against a wide range of fish pathogens (7,8), putting them on the spotlight for the development of sustainable prophylactics. Particularly, phytogenics derived from garlic (Allium sativum L., Alliaceae, Liliaceae), oregano (Oreganum vulgare, Labiateae), and thyme (Thymus vulgare, Labiateae) are among the most studied and administrated, due to their recognized health-promoting properties for aquatic species (6).…”

Antibacterial Effects of Essential Oils of Seven Medicinal-Aromatic Plants Against the Fish Pathogen Aeromonas veronii bv. sobria: To Blend or Not to Blend?

“…Several pure EOs from single MAP species have been tested to date for their antimicrobial activity against microbial pathogens of aquaculture environments with promising results [ 9 , 21 , 22 , 23 ]. However, there is limited knowledge regarding the antimicrobial activity of blended EOs [ 19 , 24 , 25 ].…”

“…To date, there are only few studies investigating the effect of EOs and their individual components against A. veronii bv. sobria [ 21 ]. Additionally, there is only limited knowledge regarding the complex interactions of blended EOs from different MAPs against the specific pathogen [ 21 ].…”

“…sobria [ 21 ]. Additionally, there is only limited knowledge regarding the complex interactions of blended EOs from different MAPs against the specific pathogen [ 21 ]. In this context, the primary aim of the present study was to investigate possible synergistic antimicrobial effects of mixed EOs from selected MAPs of Greece against A. veronii bv.…”

“…sobria . Our investigation was specifically focused on EOs from seven MAPs that showed the greatest inhibitory activity against bacterial fish pathogens in a previous screening study [ 21 ]. To this end, a total of 127 combinations of EOs from the seven selected MAPs were prepared and were tested in vitro against A. veronii bv.…”