The essential oils thymol and carvacrol applied in the packing lines avoid lemon spoilage and maintain quality during storage

Microstructural and physicochemical quality maintenance in green bell pepper infected with Botrytis cinerea and treated with thyme essential oil combined with carnauba wax

Bell pepper presents rapid weight loss and is highly susceptible to gray mold caused by the fungus Botrytis cinerea. The most employed method to control this disease is the application of synthetic fungicides such as thiabendazole (TBZ); however, its continued use causes resistance in fungi as well as environmental problems. For these reasons, natural alternatives arise as a more striking option. Currently, bell pepper fruits are coated with carnauba wax (CW) to prevent weight loss and improve appearance. Moreover, CW can be used as a carrier to incorporate essential oils, and previous studies have shown that thyme essential oil (TEO) is highly effective against B. cinerea. Therefore, this study aimed to evaluate the effect of CW combined with TEO on the development of gray mold and maintenance of microestructural and postharvest quality in bell pepper stored at 13°C. The minimal inhibitory concentration of TEO was 0.5%. TEO and TBZ provoked the leakage of intracellular components. TEO and CW + TEO treatments were equally effective to inhibit the development of gray mold. On the quality parameters, firmness and weight loss were ameliorated with CW and CW + TEO treatments; whereas lightness increased in these treatments. The structural analysis showed that CW + TEO treatment maintained the cell structure reducing the apparition of deformities. The results suggest that CW + TEO treatment could be used as a natural and effective antifungal retarding the appearance of gray mold and maintaining the postharvest quality of bell pepper. PRACTICAL APPLICATION: CW and TEO are classified as generally recognized as safe (GRAS) by the US Food and Drug Administration (FDA). This combination can be employed on the bell pepper packaging system to extend shelf life and oppose gray mold developments. Bell pepper fruits are normally coated with lipid-base coatings such as CW before commercialization; therefore, TEO addition would represent a small investment without any changes on the packaging system infrastructure.

Xanthan gum coatings augmented with lemongrass oil preserve postharvest quality and antioxidant defence system of Kinnow fruit under low-temperature storage

Kinnow mandarin is an important citrus fruit that undergoes various postharvest qualitative losses. Therefore, the present study aimed to investigate the effect of polysaccharide-based xanthan gum (XG) coatings and lemongrass essential oil (LG) on the nutritive quality of Kinnow mandarins stored at 5-7 °C, 90-95 % RH for 75 days. The results revealed that in comparison to control the coatings maintained the fruit titratable acidity (TA), soluble solid content (SSC), ascorbic acid (AsA) content, total flavonoid content (TFC), and juice content, along with reduced weight loss and spoilage incidence. The coated fruits also exhibited higher sensory quality, total antioxidant activity (TAA), and activities of enzymes; catalase (CAT), peroxidase (POD), and phenylalanine ammonia-lyase (PAL). At the end of storage, the fruits coated with XG 1.0 % + LG 1.0 % exhibited maximum TA (0.69 %), AsA content (203.5 mg L-1), and TFC (0.21 mg g-1) with minimum weight loss (7.57 %) and spoilage (3.01 %) and SSC (11.87 %). The scanning electron microscopic (SEM) images of the coated fruits also exhibited smooth surfaces with closed stomata pores. Overall, XG 1.0 % + LG 1.0 % proved as a potential postharvest treatment for maintaining the nutritive quality of Kinnow under low-temperature storage.

The Potential of Essential Oils from Active Packaging to Reduce Ethylene Biosynthesis in Plant Products. Part 1: Vegetables (Broccoli and Tomato)

Essential oils (EOs) extracted from plants have a high potential to reduce ethylene biosynthesis, although their effects have not been deeply studied yet on the key components of the ethylene biosynthesis pathway: l-aminocyclopropane-1-carboxylic (ACC) oxidase activity, ACC synthase activity, and ACC content. Hence, the present study aimed to elucidate the effects of released EOs from active packaging (with different EO doses ranging from 100 to 1000 mg m-2) on the ethylene biosynthesis key components of broccoli and tomato under different storage temperature scenarios. The largest ethylene inhibitory effects on broccoli and tomatoes were demonstrated by grapefruit EO and thyme essential EO (up to 63%), respectively, which were more pronounced at higher temperatures. Regarding EO doses, active packaging with a thyme EO dose of 1000 mg m-2 resulted in the strongest reduction (33-38%) of ethylene production in tomatoes. For broccoli, identical results were shown with a lower grapefruit EO dose of 500 mg m-2. The studied EO-active packaging decreased ACC synthase and ACC oxidase activities by 40-50% at 22 °C. Therefore, this EO-active packaging is a natural and effective technology to reduce ethylene biosynthesis in broccoli and tomatoes when they are stored, even in unsuitable scenarios at high temperatures.

Terpenic Constituents of Essential Oils with Larvicidal Activity against Aedes Aegypti: A QSAR and Docking Molecular Study

Aedes aegypti is a vector for the arbovirus responsible for yellow fever, Zika and Chikungunya virus. Essential oils and their constituents are known for their larvicidal properties and are strong candidates for mosquito control. This work aimed to develop a quantitative structure-activity study and molecular screening for the search and design of new larvicidal agents. Twenty-five monoterpenes with previously evaluated larvicidal activity were built and optimized using computational tools. QSAR models were constructed through genetic algorithms from the larvicidal activity and the calculation of theoretical descriptors for each molecule. Docking studies on acetylcholinesterase (AChE) and sterol carrier protein (SCP-2) were also carried out. Results demonstrate that the epoxide groups in the structure of terpenes hinder larvicidal activity, while lipophilicity plays an important role in enhancing biological activity. Larvicidal activity correlates with the interaction of the sterol-carrier protein. Of the 25 compounds evaluated, carvacrol showed the highest larvicidal activity with an LC₅₀ of 8.8 µg/mL. The information included in this work contributes to describing the molecular, topological, and quantum mechanical properties related to the larvicidal activity of monoterpenes and their derivatives.

Pre- or Post-Harvest Treatment with MeJA Improves Post-Harvest Storage of Lemon Fruit by Stimulating the Antioxidant System and Alleviating Chilling Injury

Cold storage preserves lemon fruit quality; however, it can result in significant chilling injury (CI). The effects of pre- and post-harvest methyl jasmonate (MeJA) treatments at four concentrations (0, 0.1, 0.3, and 0.5 mM) on CI and sensory quality of lemons during 80 d of storage at 7-10 °C were investigated. Both pre- and post-harvest MeJA treatments reduced CI, weight loss (WL) and maintained higher firmness, total soluble solids (TSS), and total acidity (TA) than in the controls. Antioxidant enzyme activities decreased in the control fruit but increased in both pre- and post-harvest MeJA-treated fruit. In addition, phospholipase D (PLD) and lipoxygenase (LOX) activities and malondialdehyde (MDA) content were higher in the control than in the MeJA-treated fruit. Pre-harvest MeJA treatment generally preserved fruit better than post-harvest MeJA treatment, with the best results observed when MeJA was applied at 0.3 mM, which enhanced the antioxidant system of the lemon fruits, thus reducing the post-harvest incidence of chilling injury. These results have important implications for improved fruit quality post-harvest.

Spray drying encapsulation of essential oils; process efficiency, formulation strategies, and applications

Essential oils (EOs) have many beneficial qualities, including antimicrobial, antioxidant, antiviral, and antifungal activities, along with good aroma, which have played a significant role in pharmaceutical, textile, and food industries. However, their high volatility and sensibility to external factors, as well as susceptibility to deterioration caused by environmental and storage conditions, or even common processing, and consequently limited water solubility, makes it difficult to incorporate them into aqueous food matrices and limits their industrial application. Spray-drying encapsulation has been proposed as a solution and a challenging research field to retard oil oxidation, extend EO's shelf life, improve their physicochemical stability, achieve controlled release, suggest novel uses, and therefore boost their added value. The objective of this review is to discuss various used wall materials, infeed emulsion properties, the main formulation and process variables affecting the physicochemical properties and release characteristics of the EOs-loaded particles obtained by spray-drying, the stability of EOs during storage, and the applications of encapsulated EOs powders in foods and nutrition, pharmaceuticals, and textile industries. The current review also summarizes recent advances in spray drying approaches for improving encapsulation efficiency, flavor retention, controlled release, and applicability of encapsulated EOs, thereby expanding their use and functionalities.

Cell wall modification and lignin biosynthesis involved in disease resistance against Diaporthe citri in harvested pummelo fruit elicited by carvacrol

BACKGROUND

Phomopsis stem-end rot caused by Diaporthe citri, causes significant commercial postharvest losses of pummelo fruit during storage. Carvacrol (CVR) is a known generally recognized as safe and has the ability to prolong the preservation of harvested fruits. In the present study, the inhibitory effects of CVR treatment at the appropriate concentration on Phomopsis stem-end rot development of harvested pummelo fruit inoculated with D. citri were evaluated by the amounts of cell wall components, the activities and gene expressions of related enzymes involved in cell wall modification and lignin biosynthesis.

RESULTS

Results indicated that CVR completely inhibited D. citri growth in vitro at 200 mg L^-1 and significantly controlled Phomopsis stem-end rot development in harvested pummelo. The CVR treatment delayed peel softening and browning, and retarded electrolyte leakage, superoxide radical (O₂ ^•- ) production, and malondialdehyde content. The CVR-treated fruit maintained higher amounts of cell wall material, protopectin, hemicelluloses, and cellulose, but exhibited lower water-soluble pectin amount. Moreover, in D. citri-inoculated fruit, CVR treatment suppressed the activities and gene expressions of cell wall disassembling-enzymes, including pectin methylesterase, polygalacturonase, cellulase, and β-galactosidase, while the development of cell wall degradation was reduced. Meanwhile, the CVR treatment enhanced the lignin biosynthesis by increasing the activities and up-regulating the gene expressions of phenylalanine ammonialyase, cinnamic alcohol dehydrogenase, and peroxidase accompanied with elevated level of lignin in pummelo fruit.

CONCLUSION

The disease resistance to D. citri in pummelo fruit elicited by CVR treatment is related to delaying cell wall degradation and enhancing lignin biosynthesis. © 2021 Society of Chemical Industry.

Production of Innovative Essential Oil-Based Emulsion Coatings for Fungal Growth Control on Postharvest Fruits

This work assessed the antimicrobial potential of natural essential oils (EOs) from cinnamon (CEO), zataria (ZEO), and satureja (SEO), applied natively or as coatings against Penicillium expansum and Botrytis cinerea during both in vitro and in vivo (on apple fruits) experiments. The induced inhibitory effect towards fungal growth, as a function of both EO type and concentration (75–1200 μL/L), was preliminarily investigated to select the most suitable EO for producing bacterial cellulose nanocrystals (BCNCs)/fish gelatin (GelA)-based emulsions. CEO and ZEO exhibited the best performances against P. expansum and B. cinerea, respectively. None of the pristine EOs completely inhibited the fungal growth and “disease severity”, properly quantified via size measurements of lesions formed on fruit surfaces. As compared to pristine CEO, coating emulsions with variable CEO concentration (75–2400 µL/L) curbed lesion spreading on apples, owing to the controlled CEO release during a 21-day temporal window. The strongest effect was displayed by BCNCs/GelA-CEO emulsions at the highest CEO concentration, upon which lesions on fruit skins were barely detectable. This work demonstrated the capability of EOs embedded in BCNCs/GelA-based nanocapsules to efficiently slow down microbial spoilage on postharvest fruits, thus offering viable opportunities for developing innovative antimicrobial packaging systems.

Thymol improves salinity tolerance of tobacco by increasing the sodium ion efflux and enhancing the content of nitric oxide and glutathione

BACKGROUND AND OBJECTIVE

Salt stress is one of the most important abiotic stresses affecting the yield and quality of tobacco (Nicotiana tabacum). Thymol (a natural medicine) has been widely used in medical research because of its antibacterial and anti-inflammatory activities. However, the influence of thymol on the root growth of tobacco is not fully elucidated. In this study, the regulatory effects of different concentrations of thymol were investigated.

METHODOLOGY

Here, histochemical staining and biochemical methods, non-invasive micro-test technology (NMT), and qPCR assay were performed to investigate the effect of thymol and mechanism of it improving salinity tolerance in tobacco seedlings.

RESULTS

In this study, our results showed that thymol rescued root growth from salt stress by ameliorating ROS accumulation, lipid peroxidation, and cell death. Furthermore, thymol enhanced contents of NO and GSH to repress ROS accumulation, further protecting the stability of the cell membrane. And, thymol improved Na+ efflux and the expression of SOS1, HKT1, and NHX1, thus protecting the stability of Na+ and K+.

CONCLUSION

Our study confirmed the protecting effect of thymol in tobacco under salt stress, and we also identified the mechanism of it, involving dynamic regulation of antioxidant system and the maintenance of Na+ homeostasis. It can be a new method to improve salinity tolerance in plants.

Antimicrobial and Anticorrosion Activity of a Novel Composite Biocide against Mixed Bacterial Strains in Taiwanese Marine Environments

Taiwan is an island with a humid subtropical climate. The relatively warm seawater results in biofouling of the surfaces of marine facilities. Biocide application is a common practice for combating and eliminating adhesive fouling. However, a single type of biocide may have limited antimicrobial effects due to the relatively high microbial diversity in marine environments. Therefore, applying a mixture of various biocides may be necessary. In this study, the antimicrobial and anticorrosion properties of a newly designed composite biocide, namely a combination of thymol and benzyldimethyldodecylammonium chloride, were investigated by applying the biocide to 304 stainless steel substrates immersed in inocula containing bacterial strains from Tamsui and Zuoying harbors. The ability of 3TB and 5TB treatments to prevent sessile cells and biofilm formation on the 304 stainless steel coupon surface was determined through scanning electron microscopy investigation. In addition, confocal laser scanning microscopy indicated that the 5TB treatment achieved a greater bactericidal effect in both the Tamsui and Zuoying inocula. Moreover, electrochemical impedance spectroscopy revealed that the diameter of the Nyquist semicircle was almost completely unaffected by Tamsui or Zuoying under the 5TB treatment. Through these assessments of antimicrobial activity and corrosion resistance, 5TB treatment was demonstrated to have superior bactericidal activity against mixed strains in both southern and northern Taiwanese marine environments.

The Effect of Controlled-Release Carvacrol on Safety and Quality of Blueberries Stored in Perforated Packaging

The objective of this research was to evaluate the use of a controlled-release carvacrol powder to delay storage decay and maintain the safety of blueberries. The controlled-release carvacrol powder was a microcapsule of carvacrol (11% (w/w) active carvacrol) surrounded by a pectin/sodium alginate matrix. The microcapsules were packed in an air-permeable pouch, and then attached to the top of a clamshell filled with blueberries. The blueberries, inoculated with Escherichia coli or Colletotrichum acutatum, or non-inoculated control, were monitored for microbial growth and quality for 10 days at 10 °C and 5 days at 20 °C. Three treatments were compared: controlled-release microencapsulated carvacrol, non-encapsulated carvacrol, and control. The results showed that both the microencapsulated carvacrol and the non-encapsulated carvacrol treatments significantly reduced the populations of yeast and mold, and of E. coli and mesophilic aerobic bacteria. The microencapsulated carvacrol treated berries retained better quality due to significantly lower weight loss than control after 10 days at 10 °C. Sensory panelists found that the microencapsulated carvacrol berries had significantly higher overall blueberry flavor and lower discernible off-flavor in comparison with the non-encapsulated treatment after 3 days at 20 °C. The fruit internal quality, including total soluble solids content (SSC), and titratable acidity (TA), was not significantly affected by any treatment. These results indicate that pectin/sodium alginate controlled-release microencapsulated carvacrol can be used for the preservation of blueberries or other small fruit.

Recent development in biological activities and safety concerns of perillaldehyde from perilla plants: A review

Monoterpene Perillaldehyde (PAE) is a major component of the essential oil extracted from perilla plants (Perilla frutescens), which has been used as a leafy vegetable and a medicinal agent. PAE has gained a lot of attention in recent years because of its antifungal and other microbial activities and, human health benefits. PAE has also been used as food additives, perfume ingredients, and traditional medicine concoctions. Biological analyses of PAE have revealed that it has good antioxidant activities and can serve as organic fruit and food preservative. Animal studies indicated potent anticancer, anti-depressant, and anti-inflammatory effects of PAE. Also, PAE is certified "generally recognized as safe" (GRAS) and not mutagenic. However, moderation during usage is advisable, as minor adverse effects are associated with a very high dosage. Despite the newly reported findings, its properties have not been thoroughly summarized and reviewed. Also, clinical trials and official large-scale field applications of PAE in the agricultural sectors are yet to be reported. In this review, updated PAE research progress was provided, focusing on its antifungal and other antimicrobial properties and the mechanisms behind it, phytochemical profile, pharmacological effects, and safety concerns.HighlightsIsolation and recovery techniques of PAE from perilla plants have been developed and improved in recent years.PAE is a potential anti-oxidant and antifungal agent that can be widely used in the food industry.PAE can be developed into drug ingredients for pharmaceutical industries due to its anti-inflammatory, anti-cancer and anti-depressant activities.PAE can be safely used in human when low and moderate dosage is used.

Studying the Ability of Thymol to Improve Fungicidal Effects of Tebuconazole and Difenoconazole Against Some Plant Pathogenic Fungi in Seed or Foliar Treatments

Thymol, a secondary plant metabolite possessing antifungal and chemosensitizing activities, disrupts cell wall or membrane integrity and interferes with ergosterol biosynthesis. Thymol also functions as a redox-active compound inducing generation of reactive oxygen species and lipid peroxidation in fungal cells. Previously, we showed thymol significantly enhanced the in vitro growth inhibitory effect of difenoconazole against Bipolaris sorokiniana and Parastagonospora nodorum. More recently, we demonstrated a possibility to use thymol to overcome the resistance of a P. nodorum strain able to grow on difenoconazole-containing media. However, potential for thymol to serve as a chemosensitizing agent in seed or plant treatments, to provide an effective suppression of the above-mentioned plant pathogens by triazole fungicides applied in lowered dosages, had yet to be tested. In the work presented here, we showed combined treatments of naturally infected barley seeds with thymol and difenoconazole (Dividend® 030 FS) synergistically exacerbated the protective effect against common root rot agent, B. sorokiniana, and other fungi (Fusarium spp. and Alternaria spp.). Similarly, co-applied treatment of wheat seeds, artificially inoculated with Fusarium culmorum, resulted in equivalent reduction of disease incidence on barley seedlings as application of Dividend®, alone, at a ten-fold higher dosage. In foliar treatments of wheat seedlings, thymol combined with Folicur® 250 EC (a.i. tebuconazole) enhanced sensitivity of P. nodorum, a glume/leaf blotch pathogen, to the fungicide and provided a significant mitigation of disease severity on treated seedlings, compared to controls, without increasing Folicur® dosages. Folicur® co-applied with thymol was also significantly more effective against a strain of P. nodorum tolerant to Folicur® alone. No additional deoxynivalenol or zearalenone production was found when a toxigenic F. culmorum was cultured in a nutrient medium containing thymol at a concentration used for chemosensitization of root rot agents. Accordingly, F. culmorum exposure to thymol at the sensitizing concentration did not up-regulate key genes associated with the biosynthesis of trichothecene or polyketide mycotoxins in this pathogen. Further studies using field trials are necessary to determine if thymol-triazole co-applications result in sensitization of seed- and foliar-associated plant pathogenic fungi, and if thymol affects production of fusarial toxins under field conditions.

Enhancing antioxidant systems by preharvest treatments with methyl jasmonate and salicylic acid leads to maintain lemon quality during cold storage

The effects of preharvest treatments with 0.1 mM methyl jasmonate (MeJA) and 0.5 mM salicylic acid (SA) on quality parameters of lemon fruit and their relationship with antioxidant systems, gene expression and bioactive compounds at harvest and during cold storage were evaluated. Results showed that total antioxidant activity, total phenolic content and the major individual phenolics (hesperidin and eriocitrin) were always higher in treated fruit than in controls. The activity of the antioxidant enzymes catalase, peroxidase and ascorbate peroxidase was also increased at harvest by SA and MeJA treatments, especially the last enzyme, for which the expression of its codifying gene was also enhanced. In addition, treated fruit had lower weight and firmness losses, respiration rate and production of ethylene than controls. Moreover, sugars and organic acids were maintained at higher concentration in flavedo and juice as a consequence of preharvest SA and MeJA treatments, showing an effect on maintaining fruit quality properties.

Effect of red thyme oil (Thymus vulgaris L.) vapours on fungal decay, quality parameters and shelf-life of oranges during cold storage

This work has been aimed at studying the effect of red thyme oil (RTO, Thymus vulgaris L.) on the shelf-life and Penicillium decay of oranges during cold storage. RTO vapours significantly reduced (P ≤ 0.05) the percentage of infected wounds, the external growth area and the production of spores in inoculated orange fruit stored for 12 days at 7 °C in a polypropylene film selected for its appropriate permeability. Among the RTO compounds, p-cymene and thymol were the most abundant in packed boxes at the end of cold storage. The RTO vapours did not affect the main quality parameters of the oranges, or the taste and odour of the juice. The results have shown that an active packaging, using RTO vapours, could be employed, by the citrus industry, to extend the shelf-life of oranges for fresh market use and juice processing.

The antibacterial properties of phenolic isomers, carvacrol and thymol

Most of the antibacterial activities of essential oils from the Lamiaceae herbaceous plant family thyme and oregano are attributed to their bioactive isomeric monoterpenoid constituents, carvacrol and thymol. Commercially available antibiotics of thymol or carvacrol have not yet been developed but health products have incorporated thymol into their formulations for their antimicrobial properties. Carvacrol and thymol are generally considered safe for consumption and they have been used in dental applications, approved as food flavorings and have been considered as antibacterial additives in food and feed. Many studies have demonstrated that carvacrol and thymol are potent antibacterial agents against both Gram-positive and Gram-negative bacteria. The most frequently reported mechanism of antibacterial action of both isomers involves the disruption of bacterial membrane leading to bacterial lysis and leakage of intracellular contents resulting in death. Other proposed mechanisms of antibacterial action include the inhibition of efflux pumps, prevention in the formation and disruption of preformed biofilms, inhibition of bacterial motility, and inhibition of membrane ATPases. In addition, both isomers have been found to act additively or synergistically with conventional antibiotics important in overcoming the problem of bacteria resistance in food and disease.

Pre-harvest methyl jasmonate treatments increase antioxidant systems in lemon fruit without affecting yield or other fruit quality parameters

BACKGROUND

Jasmonic acid (JA) and its volatile derivative methyl jasmonate (MeJA) are hormones involved in the regulation of many processes in plants and act (when applied as a post- or pre-harvest treatment) to increase fruit bioactive compounds with antioxidant potential. However, there is no literature available regarding the effect of pre-harvest MeJA treatment on lemon fruit antioxidant systems, which was the aim of the present study.

RESULTS

MeJA treatment (0.1, 0.5 and 1.0 mmol L^-1 ) increased antioxidant compounds, such as phenolics, in the juice and flavedo of 'Fino' and 'Verna' lemons at harvest, with the most effective concentration being 0.1 mmol L^-1 in both cultivars. In addition, catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) activities were also increased by MeJA treatment, with the highest increases being also found with 0.1 mmol L^-1 . The increases in APX and CAT were maintained from one treatment to another during fruit development on the tree, whereas the increase on POD disappeared after 8-10 days of each treatment. For both antioxidant systems, the highest increases were found in lemon harvested at the commercial ripening stage. By contrast, crop yield, fruit ripening process and quality parameters were generally not affected by MeJA treatment.

CONCLUSION

Preharvest MeJA treatment could be a useful tool for increasing antioxidant potential and the health beneficial effects of lemon fruit consumption, given the relationship between these properties and phenolic content. Moreover, the increased concentration of phenolics and the activity of antioxidant enzymes in the flavedo of MeJA treated fruit could increase lemon tolerance to chilling injury and decay during postharvest storage. © 2019 Society of Chemical Industry.

Effect of Thymol and Carvacrol Encapsulated in Hp-Β-Cyclodextrin by Two Inclusion Methods against Geotrichum citri-aurantii

Geotrichum citri-aurantii causes sour rot in citrus fruits and is responsible for important economic losses during storage. However, the availability of chemical fungicides for the control of this pathogen is limited. Thus, the aim of this research was to evaluate the antifungal efficacy of thymol and carvacrol encapsulated in 2-hydroxylpropyl-beta-cyclodextrin (HP-β-CD) (prepared by the microwave irradiation method [MW] and solubility method [S]) for inhibition of G. citri-aurantii using in vitro bioassays broth (micro and macrodilutions methods) and inoculated food testing. Both encapsulated thymol and carvacrol were shown to be effective for inhibiting G. citri-aurantii growth in in vitro assays. Thymol was more effective in inhibiting G. citri-aurantii, while better encapsulation was provided by MW. HP-β-CD-thymol encapsulated by MW (HP-β-CD-thymol-MW) showed the lowest 50% effective dose (ED₅₀ = 1.16 mM), minimum inhibitory concentration (MIC = 5.06 mM), and minimum fungicide concentration (MFC = 52.6 mM). HP-β-CD-thymol-MW was found highly effective in reducing the growth rate and mycelial growth inhibition. Finally, HP-β-CD-thymol-MW and HP-β-CD-carvacrol-MW showed a higher persistent effect than thymol and carvacrol in their natural form in inhibiting this fungus. Therefore, HP-β-CD-thymol-MW could be a promising alternative to synthetic fungicides for controlling G. citri-aurantii, the causal agent of citrus sour rot. PRACTICAL APPLICATION: Encapsulated thymol and carvacrol in HP-β-Cyclodextrins are effective for controlling G. citri-aurantii in in vitro experiments. Encapsulation of thymol and carvacrol by microwave irradiation method (MW) was more effective than the solubility (S) method. Thymol was more effective than carvacrol, and the best results on G. citri-auriantii inhibition were achieved using the HP-β-CD-thymol-MW method (which gave the lowest ED₅₀ , MIC, and MFC).

Coating Satsuma mandarin using grapefruit seed extract-incorporated carnauba wax for its preservation

Grapefruit seed extract (GSE)-incorporated carnauba wax (CW) coating was developed to preserve Satsuma mandarins (Citrus unshiu Marc.). GSE (1.00%, w/w)-incorporated CW (GSE-CW) coating emulsions and GSE (0.50%)-oregano oil (OO, 0.50%)-incorporated CW (GSE-OO-CW) coating emulsions reduced Penicillium italicum disease incidence (%) on mandarin surfaces by 23.6 ± 3.6 and 25.0 ± 5.0%, respectively, relative to that on uncoated mandarin samples (100%). GSE (1.00%)-CW coating emulsions exhibited a higher colloidal stability than GSE (0.50%)-OO (0.50%)-CW coating emulsions. During storage at 25 °C, GSE (1.00%)-CW coating was superior to CW coating in reducing P. italicum disease incidence. CW coating significantly reduced weight loss, respiration rate, and firmness loss during storage at 4 and 25 °C (P < 0.05). The ascorbic acid concentration and peel color were not affected by GSE-CW coating (P > 0.05). These results suggest that GSE-CW coating can extend the post-harvest shelf life of mandarins by inhibiting the growth of P. italicum.

Biocidal effect of thymol and carvacrol on aquatic organisms: Possible application in ballast water management systems

Ballast water is essential for maintaining the balance and integrity of a ship. However, exchanging ballast water resulted in discharging water of different origins in vessel recipient ports, and this may have caused ecosystem disturbance or aquatic pollution. The ballast water management (BWM) system is essential for the purification and disinfection of the ballast water that is taken up. Because current BWM systems widely use biocides for the treatment of aquatic organisms, the biocides may result in unintended toxicity of the discharged ballast water. In this study, we suggested thymol and carvacrol as chemical biocides for BWM systems and investigated their effectiveness using Artemia salina and Escherichia coli. Thymol and carvacrol showed biocidal effects in our study. A combination of these substances showed a synergistic increase in the biocidal effects. Moreover, carvacrol naturally degrades after disinfection, which indicates that natural substances may be promising candidates to increase the efficacy and reduce unwanted side effects of the BWM system.

Perillaldehyde Controls Postharvest Black Rot Caused by Ceratocystis fimbriata in Sweet Potatoes

Black rot caused by Ceratocystis fimbriata is the most damaging postharvest disease among sweet potatoes. Black rot can be controlled by synthetic fungicides, but these synthetic fungicides also have several negative effects. Perillaldehyde (PAE), a major component of the herb perilla, is an effective and eco-friendly method of controlling this disease. The antifungal activity of PAE on the mycelial growth in C. fimbriata was evaluated in vitro. Sweet potatoes at the postharvest stage were surfaced-disinfected with 75% ethanol. Artificially created wounds were inoculated with a C. fimbriata cell suspension, and then, the PAE was spontaneously volatilized inside the residual airspace of the containers at 28°C. Samples were collected at 0, 3, 6, 9, 12, 15, 18, and 21 days from each group, and the tissues around the wounds of the sweet potatoes were collected using a sterilized knife and then homogenized to determine their defense-related enzyme activity and quality parameters. In vitro assays showed that the mycelial growth of C. fimbriata was inhibited by PAE in a dose-dependent manner. An in vivo test demonstrated that 25, 50, and 100 μl/l PAE doses, when applied to sweet potatoes inoculated with C. fimbriata, could remarkable lower lesion diameter as compared to the control. Even though the storage time was prolonged, PAE vapor treatment still drastically inhibited sweet potato decay during storage at 28°C. These PAE vapor treatments also enhanced the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL). These treatments remarkably decreased weight loss rates and had minor effects on other fruit quality parameters, such as anthocyanin content and vitamin C content. In our study, the results suggested that the effects of PAE on postharvest sweet potatoes may be attributed to the maintenance of enzymatic activity and fruit quality. In sum, PAE may be a promising approach to controlling C. fimbriata in sweet potatoes.

Essential oils and their components as an alternative in the control of mosquito vectors of disease

More than half of the human population is exposed to mosquito-borne infections. Climate change and the emergence of strains resistant to traditionally used insecticides have motivated the search of new agents for mosquito population control. Essential oils have been effective repellents and larvicidal agents.The aim of this work was to review research studies conducted in recent years on the larvicidal activity of essential oils and their components against Aedes, Anopheles and Culex mosquitoes, as well as the latest reports about their possible mechanism of action.

Thymol Mitigates Cadmium Stress by Regulating Glutathione Levels and Reactive Oxygen Species Homeostasis in Tobacco Seedlings

Thymol is a famous plant-derived compound that has been widely used in pharmacy due to its antioxidant and antimicrobial properties. However, the modulation of intrinsic plant physiology by thymol remains unclear. It is a significant challenge to confer plant tolerance to Cd (cadmium) stress. In the present study physiological, histochemical, and biochemical methods were applied to investigate thymol-induced Cd tolerance in tobacco (Nicotiana tabacum) seedlings. Thymol was able to alleviate Cd-induced growth inhibition of tobacco seedlings in both dose- and time-dependent manners. Both histochemical detection and in-tube assays suggested that thymol treatment blocked Cd-induced over-generation of reactive oxygen species (ROS), lipid peroxidation, and loss of membrane integrity in both leaves and roots. Thymol decreased Cd-induced cell death that was indicated in vivo by propidium iodide (PI) and trypan blue, respectively. Thymol stimulated glutathione (GSH) biosynthesis by upregulating the expression of γ-glutamylcysteine synthetase 1 (GSH1) in Cd-treated seedlings, which may contribute to the alleviation of Cd-induced oxidative injury. In situ fluorescent detection of intracellular Cd2+ revealed that thymol significantly decreased free Cd2+ in roots, which could be explained by the thymol-stimulated GSH biosynthesis and upregulation of the expression of phyochelatin synthase 1 (PCS1). Taken together, these results suggested that thymol has great potential to trigger plant resistant responses to combat heavy metal toxicity, which may help our understanding of the mechanism for thymol-modulated cell metabolic pathways in response to environmental stimuli.

The Fungicidal Activity of Thymol against Fusarium graminearum via Inducing Lipid Peroxidation and Disrupting Ergosterol Biosynthesis

Thymol is a natural plant-derived compound that has been widely used in pharmaceutical and food preservation applications. However, the antifungal mechanism for thymol against phytopathogens remains unclear. In this study, we identified the antifungal action of thymol against Fusarium graminearum, an economically important phytopathogen showing severe resistance to traditional chemical fungicides. The sensitivity of thymol on different F. graminearum isolates was screened. The hyphal growth, as well as conidial production and germination, were quantified under thymol treatment. Histochemical, microscopic, and biochemical approaches were applied to investigate thymol-induced cell membrane damage. The average EC₅₀ value of thymol for 59 F. graminearum isolates was 26.3 μg·mL⁻¹. Thymol strongly inhibited conidial production and hyphal growth. Thymol-induced cell membrane damage was indicated by propidium iodide (PI) staining, morphological observation, relative conductivity, and glycerol measurement. Thymol induced a significant increase in malondialdehyde (MDA) concentration and a remarkable decrease in ergosterol content. Taken together, thymol showed potential antifungal activity against F. graminearum due to the cell membrane damage originating from lipid peroxidation and the disturbance of ergosterol biosynthesis. These results not only shed new light on the antifungal mechanism of thymol, but also imply a promising alternative for the control of Fusarium head blight (FHB) disease caused by F. graminearum.

Antifungal Edible Coatings for Fresh Citrus Fruit: A Review

According to their origin, major postharvest losses of citrus fruit are caused by weight loss, fungal diseases, physiological disorders, and quarantine pests. Cold storage and postharvest treatments with conventional chemical fungicides, synthetic waxes, or combinations of them are commonly used to minimize postharvest losses. However, the repeated application of these treatments has led to important problems such as health and environmental issues associated with fungicide residues or waxes containing ammoniacal compounds, or the proliferation of resistant pathogenic fungal strains. There is, therefore, an increasing need to find non-polluting alternatives to be used as part of integrated disease management (IDM) programs for preservation of fresh citrus fruit. Among them, the development of novel natural edible films and coatings with antimicrobial properties is a technological challenge for the industry and a very active research field worldwide. Chitosan and other edible coatings formulated by adding antifungal agents to composite emulsions based on polysaccharides or proteins and lipids are reviewed in this article. The most important antifungal ingredients are selected for their ability to control major citrus postharvest diseases like green and blue molds, caused by Penicillium digitatum and Penicillium italicum, respectively, and include low-toxicity or natural chemicals such as food additives, generally recognized as safe (GRAS) compounds, plant extracts, or essential oils, and biological control agents such as some antagonistic strains of yeasts or bacteria.