Control of postharvest diseases caused by Penicillium spp. with myrtle leaf phenolic extracts: in vitro and in vivo study on mandarin fruit during storage

Examination of genetic lines of Myrtus communis as potential sources of organic agricultural pest control agents

Myrtus communis is a Mediterranean shrub cultivated in Israel for traditional, ceremonial use only, with more than 98 % of the crop biomass, equivalent to 26-27 tons per ha per annum, considered agricultural waste. Therefore, potentially profitable use for this excess is being highly sought. As Myrtus is also known for its unique terpene and terpenoid content, this work evaluated the impact of essential oil (EO) extracted from several M. communis cultivars on storage insects, nematodes, fungi, and pathogens. In addition, the allelopathic effect of M. communis litter on the germination success of wheat seeds was evaluated. The EO extracts demonstrated an insecticidal effect on several storage insects in fumigation experiment and a potentially inhibiting effect on wheat development in allelopathy experiments. No significant impact of M. communis EOs on the examined fungi, pathogens, and nematodes was recorded. Additional uses of the M. communis biomass suggest supplying additional income to the farmer through the circular agriculture approach. In addition, the use of this local crop can contribute to sustainable intensification by increasing farming efficiency, providing nature-based substitutes for chemical pesticides, and possibly, improving the future design of agriculture through the integration of Myrtus in monoculture crops.

Myrtle: a versatile medicinal plant

Myrtus, commonly called myrtle, is a genus of flowering plants in the Myrtaceae family. This study aimed to review myrtle's pharmaceutical, food, and other uses. The pharmacological effects of myrtle for antioxidant, antibacterial, and anti-inflammatory activities, reduction of COVID-19 symptoms, anti-diabetic in the animal model, hepatoprotective in the rat model, antihypertensive, control of intestinal helminthiasis in mice model, inhibition of glucosyltransferase activity, protective effect on oxidative metabolism in the hypothyroidism model, and reducing the damage caused by skin burns are reviewed. In addition, the food uses of this plant such as improving the oxidative and microbial stability of products containing salmon, antimicrobial activity in meat and dairy products, flavoring in sea salt, microbial improvement of fresh fruits during post-harvest storage, animal nutrition, and bio-oil production are summarized.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41110-023-00194-y.

Isolation, identification, biological characteristics, and antifungal efficacy of sodium bicarbonate combined with natamycin on Aspergillus niger from Shengzhou nane (Prunus salicina var. taoxingli) fruit

The fungi causing fruit rot were isolated from symptomatic Shengzhou nane (Prunus salicina var. taoxingli) fruit and were identified as Aspergillus niger by biological characteristics and molecular analysis of the internal transcribed spacer region (rDNA-ITS) and translation elongation factor-1α (TEF-1α) sequences. Optimal growth conditions for A. niger were 30°C, pH 5.0-6.0, and fructose and peptone as carbon and nitrogen sources. The effects of sodium bicarbonate (SBC), natamycin (NT), and combined treatments on A. niger inhibition were investigated. Treatment with 4.0 g/L sodium bicarbonate (SBC) + 5.0 mg/L natamycin (NT) inhibited mycelial growth and spore germination as completely as 12.0 mg/L SBC or 25.0 mg/L NT. SBC and NT treatments disrupted the structural integrity of cell and mitochondria membranes and decreased enzyme activities involved in the tricarboxylic acid (TCA) cycle, mitochondrial membrane potential (MMP), ATP production in mitochondria, and ergosterol content in the plasma membrane, thus leading to the inhibition of A. niger growth. Moreover, experimental results in vivo showed that the rot lesion diameter and decay rate of Shengzhou nane fruit treated with SBC and NT were significantly reduced compared with the control. The results suggest that the combination treatment of SBC and NT could be an alternative to synthetic fungicides for controlling postharvest Shengzhou nane decay caused by A. niger.

Sustainable Extraction Methods Affect Metabolomics and Oxidative Stability of Myrtle Seed Oils Obtained from Myrtle Liqueur By-Products: An Electron Paramagnetic Resonance and Mass Spectrometry Approach

Myrtle liqueur production generates high amounts of by-products that can be employed for the extraction of bioactive compounds. Bio-based, non-toxic and biodegradable solvents (ethyl acetate and 2-methyltetrahydrofuran), and a mechanical extraction were applied to myrtle seeds, by-products of the liqueur production, to extract oils rich in phenolic compounds. The oils obtained were characterized for yield, peroxide value (PV), lipid composition, and total phenolic concentration (TPC). The phenolic profile of the oils, determined by LC-MS, the antioxidant activity, and the oxidative stability were also analyzed. A validated UHPLC-ESI-QTRAP-MS/MS analytical method in multiple reaction monitoring (MRM) mode was applied to quantify myricetin and its main derivatives in myrtle oils. The results pointed out clear differences among extraction methods on myricetin concentration. The oxidative stability of myrtle oils was studied with electron paramagnetic resonance (EPR) spectroscopy highlighting the effect of the extraction method on the oxidation status of the oils and the role of phenolic compounds in the evolution of radical species over time. A principal component analysis applied to LC-MS data highlighted strong differences among phenolic profiles of the oils and highlighted the role of myricetin in the oxidative stability of myrtle oils. Myrtle oil, obtained from the by-products of myrtle liqueur processing industry, extracted with sustainable and green methods might have potential application in food or cosmetic industries.

Myrtle-Functionalized Nanofibers Modulate Vaginal Cell Population Behavior While Counteracting Microbial Proliferation

Vaginal infections affect millions of women annually worldwide. Therapeutic options are limited, moreover drug-resistance increases the need to find novel antimicrobials for health promotion. Recently phytochemicals were re-discovered for medical treatment. Myrtle (Myrtus communis L.) plant extracts showed in vitro antioxidant, antiseptic and anti-inflammatory properties thanks to their bioactive compounds. The aim of the present study was to create novel nanodevices to deliver three natural extracts from leaves, seeds and fruit of myrtle, in vaginal milieu. We explored their effect on human cells (HeLa, Human Foreskin Fibroblast-1 line, and stem cells isolated from skin), resident microflora (Lactobacillus acidophilus) and on several vaginal pathogens (Trichomonas vaginalis, Escherichia coli, Staphylococcus aureus, Candida albicans, Candida kefyr, Candida glabrata, Candida parapsilosis, Candida krusei). Polycaprolactone-Gelatin nanofibers encapsulated with leaves extract and soaked with seed extracts exhibited a different capability in regard to counteracting microbial proliferation. Moreover, these nanodevices do not affect human cells and resident microflora viability. Results reveal that some of the tested nanofibers are interesting candidates for future vaginal infection treatments.

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.

Carvacrol delays Phomopsis stem-end rot development in pummelo fruit in relation to maintaining energy status and antioxidant system

Pummelo fruit rapidly depreciate in commodity value due to postharvest fungal decay and fruit quality deterioration. Here, we used carvacrol (CVR) to control Phomopsis stem-end rot (SER) caused by Diaporthe citri in pummelo fruit stored at 25 °C. Antifungal activity of CVR inhibited D. citri growth and Phomopsis SER development. Harvested pummelo fruit treated with CVR delayed firmness loss and lowered electrolyte leakage, and retarded hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulation. Unlike the control fruit, the CVR-treated fruit maintained higher levels of adenosine triphosphate and energy charge, and increased ATPase, succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and cytochrome C oxidase (CCO) activities, along with up-regulated expression levels of the respective genes. CVR improved the antioxidant capacity, as evidenced by higher non-enzymatic antioxidants amounts, higher activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR), and up-regulated expression levels of ROS-scavenging-related genes. Collectively, CVR treatment maintained the energy status and antioxidant capacity in D. citri-infected pummelo fruit, which revealed antifungal mechanisms critical for controlling postharvest fungal diseases.