Application of Thymol Vapors to Control Postharvest Decay Caused by Penicillium digitatum and Lasiodiplodia theobromae in Grapefruit.

Two of the major postharvest diseases impacting grapefruit shelf life and marketability in the state of Florida (USA) are stem-end rot (SER) caused by Lasiodiplodia theobromae and green mold (GM) caused by Penicillium digitatum. Here, we investigated the in vitro and in vivo efficacy of vapors of thymol, a natural compound found in the essential oil of various plants and the primary constituent of thyme (Thymus vulgaris) oil, as a potential solution for the management of GM and SER. Thymol vapors at concentrations lower than 10 mg L-1 significantly inhibited the mycelial growth of both pathogens, causing severe ultrastructural damage to P. digitatum conidia. In in vivo trials, the incidence and lesion area of GM and SER on inoculated grapefruit were significantly reduced after a 5 d exposure to 50 mg L-1 thymol vapors. In addition, the in vitro and in vivo sporulation of P. digitatum was suppressed by thymol. When applied in its vapor phase, thymol had no negative effect on the fruit, neither introducing perceivable off-flavor nor causing additional weight loss. Our findings support the pursuit of further studies on the use of thymol, recognized as safe for human health and the environment, as a promising strategy for grapefruit postharvest disease management.

Synergistic effects of combined cinnamaldehyde and nonanal vapors against Aspergillus flavus.

This study evaluated the synergistic antifungal effects of vapor-phase natural agents against Aspergillus flavus with an aim to prevent fungal contamination in agricultural products. Screening different combinations of natural antifungal vapor agents using the checkerboard assay revealed that the cinnamaldehyde and nonanal (SCAN) blend could exert the strongest synergistic antifungal activities against A. flavus, with a minimum inhibitory concentration (MIC) of 0.03 µL/mL, which caused a 76 % decrease in fungal population compared to when each agent was used separately. Subsequent gas chromatography-mass spectrometry (GC/MS) analysis demonstrated that the cinnamaldehyde/nonanal combination was stable and no effects on their individual molecular structures. SCAN at 2 × MIC completely inhibited the fungal conidia production and mycelial growth. The calcofluor white (CFW) and dichloro-dihydro-fluorescein diacetate (DCFH-DA) staining assays showed that SCAN treatment could accelerate the destruction of cell wall integrity and accumulation of reactive oxygen species (ROS) in A. flavus. Moreover, pathogenicity assay indicated that in contrast to separate treatment with cinnamaldehyde or nonanal, SCAN could cause a decrease in the production of A. flavus asexual spores and AFB1 on peanuts, which verified its potential synergistic activity against fungal propagation. In addition, SCAN effectively preserves the organoleptic and nutritional properties of stored peanuts. Overall, our findings strongly indicated that the cinnamaldehyde/nonanal combination is a potentially significant antifungal agent against A. flavus contamination during the postharvest storage of peanuts.

Ultrastructural Damages to H1N1 Influenza Virus Caused by Vapor Essential Oils.

Influenza viruses are transmitted from human to human via airborne droplets and can be transferred through contaminated environmental surfaces. Some works have demonstrated the efficacy of essential oils (EOs) as antimicrobial and antiviral agents, but most of them examined the liquid phases, which are generally toxic for oral applications. In our study, we describe the antiviral activity of Citrus bergamia, Melaleuca alternifolia, Illicium verum and Eucalyptus globulus vapor EOs against influenza virus type A. In the vapor phase, C. bergamia and M. alternifolia strongly reduced viral cytopathic effect without exerting any cytotoxicity. The E. globulus vapor EO reduced viral infection by 78% with no cytotoxicity, while I. verum was not effective. Furthermore, we characterized the EOs and their vapor phase by the head-space gas chromatography-mass spectrometry technique, observing that the major component found in each liquid EO is the same one of the corresponding vapor phases, with the exception of M. alternifolia. To deepen the mechanism of action, the morphological integrity of virus particles was checked by negative staining transmission electron microscopy, showing that they interfere with the lipid bilayer of the viral envelope, leading to the decomposition of membranes. We speculated that the most abundant components of the vapor EOs might directly interfere with influenza virus envelope structures or mask viral structures important for early steps of viral infection.

Evaluation of effects of essential oil vapors on the bacterial count in bioaerosols.

Background: The aerosols generated during dental treatments contain bacteria and other microorganisms that penetrate the body through the respiratory system of dental surgeons and cause infectious diseases. Several studies have been done to reduce these hazards. The aim of the present study is to evaluate the effects of the plant extract essential oil (EO) vapors of Neem, Clove, Cinnamon bark, Thyme, Lemon Grass, and Eucalyptus on the bacterial count in bioaerosols near dental units. Materials and Methods: Sampling was taken on nutrient blood agar plates by placing them open near dental units using passive air sampling method, before commencement of treatment for 1 h, during treatments for 2 h, and after introducing EO vapors for 2 h. The collected samples were taken for incubation at 37°C for 48 h. The colonies formed were counted in colony-forming units per cubic meter and taken for statistical analysis. Results: After comparing the obtained results, it was found that there was a significant reduction (P < 0.05) in the bacterial count for about 43% near the dental units after the introduction of the EO vapours. Conclusion: It is concluded that natural extracts like EOs can reduce bacterial contamination near dental units in the vapourized state, thereby reducing the health hazards in Dental Health Professionals.

A Comprehensive Review on the Impact of Edible Coatings, Essential Oils, and Their Nano Formulations on Postharvest Decay Anthracnose of Avocados, Mangoes, and Papayas.

Subtropical fruit such as avocados (Persea americana), mangoes (Mangifera indica L.), and papayas (Carica papaya L.) are economically important in international trade and predominantly exported to European destinations. These fruits are highly consumed due to their health benefits. However, due to long-distance shipping and the time required to reach the retail department stores, postharvest losses, due to postharvest decay occurring during the supply chain, affect the fruit quality on arrival at the long-distance distribution points. Currently, the use of synthetic fungicide, Prochloraz®, is used at the packing line to reduce postharvest decay and retain the overall quality of mangoes and avocados. Due to the ban imposed on the use of synthetic fungicides on fresh fruit, several studies have focused on the development of alternative technologies to retain the overall quality during marketing. Among the developed alternative technologies for commercial adoption is the use of edible coatings, such as chitosan biocontrol agents and essential oil vapors. The objective of this review is to summarize and analyze the recent advances and trends in the use of these alternative postharvest treatments on anthracnose decay in avocados, mangoes, and papayas.