Creation of New Oregano Genotypes with Different Terpene Chemotypes via Inter- and Intraspecific Hybridization.

Oregano is a medicinal and aromatic plant of value in the pharmaceutical, food, feed additive, and cosmetic industries. Oregano breeding is still in its infancy compared with traditional crops. In this study, we evaluated the phenotypes of 12 oregano genotypes and generated F1 progenies by hybridization. The density of leaf glandular secretory trichomes and the essential oil yield in the 12 oregano genotypes varied from 97-1017 per cm2 and 0.17-1.67%, respectively. These genotypes were divided into four terpene chemotypes: carvacrol-, thymol-, germacrene D/ß-caryophyllene-, and linalool/ß-ocimene-type. Based on phenotypic data and considering terpene chemotypes as the main breeding goal, six oregano hybrid combinations were performed. Simple sequence repeat (SSR) markers were developed based on unpublished whole-genome sequencing data of Origanum vulgare, and 64 codominant SSR primers were screened on the parents of the six oregano combinations. These codominant primers were used to determine the authenticity of 40 F1 lines, and 37 true hybrids were identified. These 37 F1 lines were divided into six terpene chemotypes: sabinene-, ß-ocimene-, γ-terpinene-, thymol-, carvacrol-, and p-cymene-type, four of which (sabinene-, ß-ocimene-, γ-terpinene-, and p-cymene-type) were novel (i.e., different from the chemotypes of parents). The terpene contents of 18 of the 37 F1 lines were higher than those of their parents. The above results lay a strong foundation for the creating of new germplasm resources, constructing of genetic linkage map, and mapping quantitative trait loci (QTLs) of key horticultural traits, and provide insights into the mechanism of terpenoid biosynthesis in oregano.

Unraveling the Biosynthesis of Carvacrol in Different Tissues of Origanum vulgare.

Origanum vulgare, belonging to the Lamiaceae family, is a principal culinary herb used worldwide which possesses great antioxidant and antibacterial properties corresponding to various volatile organic components (VOCs). However, the metabolite profiles and underlying biosynthesis mechanisms of elaborate tissues (stems, leaves, bracts, sepals, petals) of Origanum vulgare have seldom been reported. Here, solid-phase microextraction-gas chromatography/mass spectrometry results showed that Origanum vulgare 'Hot and Spicy' (O. vulgare 'HS') was extremely rich in carvacrol and had the tissue dependence characteristic. Moreover, a full-length transcriptome analysis revealed carvacrol biosynthesis and its tissue-specific expression patterns of 'upstream' MVA/MEP pathway genes and 'downstream' modifier genes of TPSs, CYPs, and SDRs. Furthermore, the systems biology method of modular organization analysis was applied to cluster 16,341 differently expressed genes into nine modules and to identify significant carvacrol- and peltate glandular trichome-correlated modules. In terms of these positive and negative modules, weighted gene co-expression network analysis results showed that carvacrol biosynthetic pathway genes are highly co-expressed with TF genes, such as ZIPs and bHLHs, indicating their involvement in regulating the biosynthesis of carvacrol. Our findings shed light on the tissue specificity of VOC accumulation in O. vulgare 'HS' and identified key candidate genes for carvacrol biosynthesis, which would allow metabolic engineering and breeding of Origanum cultivars.

Comparison of Origanum Essential Oil Chemical Compounds and Their Antibacterial Activity against Cronobacter sakazakii.

Origanum vulgare L. (oregano) is an aromatic plant with wide applications in the food and pharmaceutical industries. Cronobacter sakazakii, which has a high detection rate in powdered infant formula, adversely impacts susceptible individuals. Oregano essential oil (OEO) is a natural antibacterial agent that can be used to fight bacterial contamination. Here, OEO chemical compounds from eight oregano varieties were analyzed by gas chromatography-mass spectrometry and their antibacterial properties were assessed. The eight OEOs were clustered into two groups and were more diverse in group 2 than in group 1. Six compounds, including p-cymene, 3-thujene, γ-terpinene, thymol, carvacrol, and caryophyllene, were shared by eight OEOs. Among the eight oregano varieties, OEOs from O. vulgare sc2 had the strongest antibacterial activity against C. sakazaki, with the inhibition zone of 18.22mm. OEOs from O. vulgare jx, O. 'Nvying', O. vulgare 'Ehuang', and O. vulgare ssp. virens were also potent. Moreover, the antibacterial activity of OEOs was positively correlated with the relative content of thymol. As the main OEO antibacterial compound, thymol affected the normal growth and metabolism of C. sakazakii cells by destroying the bacterial membrane and decreasing the intracellular ATP concentration. Thus, in light of the antibacterial activity detected in the OEOs from the eight oregano varieties, this study provides a theoretical foundation for oregano cultivar management and development.

pH-responsive chitosan-based film containing oregano essential oil and black rice bran anthocyanin for preserving pork and monitoring freshness.

This study developed an intelligent and antibacterial packaging film using a chitosan matrix embedding oregano essential oil (OEO) and black rice bran anthocyanin (BRBA). Herein, OEO and BRBA were immobilized into the chitosan matrix through noncovalent bonds and uniformly distributed in the films. The chitosan-OEO-BRBAⅡ film exhibited excellent mechanical, antibacterial, antioxidant, and UV-vis light barrier properties, and sensitive and rapid response to pH/NH3. Furthermore, fresh pork was coated with the film for monitoring the freshness and preservation efficiency at 4 °C for 12 days. The film effectively improved the quality indices of pork, including the sensory index, total viable counts, pH, TVB-N value, and color of pork during the storage at 4 °C. The film reduced the abundance of spoilage bacteria related to stress tolerance, pathogenicity, and biofilm formation in the pork. Their odorous volatiles appeared later and were less than those in the untreated group.

Multidimensional exploration of essential oils generated via eight oregano cultivars: Compositions, chemodiversities, and antibacterial capacities.

Numerous species of Origanum (Lamiaceae) have been widely used as spices to extend the shelf life of foods. Essential oils extracted from this genus have attracted much attention owing to their potential applications as bactericides. Here, we evaluated the chemical compositions of eight oregano essential oils (OEOs) using gas chromatography-mass spectrometry and assessed their antibacterial activities. The chemical compositions of OEOs were affected by the cultivar factor, and seven common compounds, including carvacrol, were identified among eight OEOs. Partial least squares discriminant analysis enabled the distinction of three groups among these OEOs, as characterized by the proportions of carvacrol, thymol, and sesquiterpenes. OEOs effectively inhibited Escherichia coli and Staphylococcus aureus with varying antibacterial activities. Spearman correlation network highlighted core antibacterial contributors in the chemical profiles of OEOs. Our results revealed that the bacteriostatic effects of OEOs could be explained by core compounds and their synergistic effects.

A Carvacrol-Rich Essential Oil Extracted From Oregano (Origanum vulgare "Hot & Spicy") Exerts Potent Antibacterial Effects Against Staphylococcus aureus.

Oregano essential oil (OEO), as a natural antimicrobial, has gained increased interest from food researchers and manufacturers. However, a few studies have investigated its possible antibacterial effects against Staphylococcus aureus using the proteomic tool. The present study aimed to explore the antibacterial effect and mechanism of a carvacrol-rich OEO extracted from Origanum vulgare "Hot & Spicy" on the inactivation of S. aureus. The gas chromatography-mass spectrometry analysis of the OEO allowed the detection of 27 compounds; the major constituent was carvacrol (84.38% of total compounds). The average diameter of the inhibitory zone (DIZ) value was 29.10 mm, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of OEO against S. aureus were 0.125 and 0.25 mg/mL, respectively. The growth curve assay indicated that the OEO prolonged the lag phase of S. aureus. The decrease in cell viability, changes in the integrity of cell membrane, and abnormal cell morphology further reflected the cell damage of S. aureus caused by the OEO. In addition, a label-free proteomic analysis was applied to analyze the regulatory networks of S. aureus in response to 1/2 MIC OEO-treatment stress. Of the 56 differentially expressed proteins (DEPs) identified, 26 were significantly upregulated and 30 downregulated. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that the DEPs were mainly involved in pathways of ribosomes; valine, leucine, and isoleucine biosynthesis; and phenylalanine, tyrosine, and tryptophan biosynthesis, which suggested that the growth inhibition of S. aureus might be due to the disordered effect of the OEO on protein synthesis and amino acid metabolism. These findings deepened our understanding regarding S. aureus survival and metabolism responses to the OEO treatment and suggested that the carvacrol-rich OEO could be used in food production environments to effectively control S. aureus.

Comparison of Nutritional Compositions and Essential Oil Profiles of Different Parts of a Dill and Two Fennel Cultivars.

Fennel and dill are widely used as food additives owing to their various biological activities, such as antioxidants, antimicrobials, food-preservatives, and seasoning capacities. Herein, the nutritional composition and essential oil (EO) chemical profiles of fruits, umbels, stalks, and roots from one dill and two fennel cultivars were evaluated. The fruits had the highest content of crude protein (≥15%), crude fat (≥8%), and phosphorus (≥0.5%), and exhibited the highest total energy (≥20 MJ/kg) and EO yield (≥2%). Moreover, estragole (86.56% in Fdf), anethole (71.17% in Fhf), fenchone (16.74% in Fhf), limonene (50.19% in Agf), and carvone (42.41% in Agf) were the main components of the EOs generated from the fruits. The chemical profiles of EOs in the roots were significantly different from those of the aerial parts of the fennel and dill; thus, the roots and aerial parts could be distinguished based on myristicin (Variable Importance in Projection (VIP) = 1.90399) and apiol (VIP = 1.85922). The EO components of the aerial parts varied remarkably, and the chemical markers for differentiating these three cultivars were anethole (VIP = 1.36571), estragole (VIP = 1.30292), and carvone (VIP = 1.11947). Overall, our results provide a noteworthy chemical basis for further development of fennel and dill, especially as food additives.

Analysis of the Chemical Profiles and Anti-S. aureus Activities of Essential Oils Extracted from Different Parts of Three Oregano Cultivars.

The use of antibiotics in the food industry is highly regulated owing to the potential harmful effects of antibiotics on human health. Therefore, it is crucial to seek alternatives for ensuring food safety. Essential oils (EOs) extracted from plants of the genus Origanum exhibit a wide range of chemical and antibacterial activities. Species and tissue factors shape the production and accumulation processes of EOs in Origanum plants, thereby affecting their bactericidal activity. In this study, the morphologies and EO yields from the inflorescences, leaves, and stems of three oregano cultivars were evaluated. In addition, the chemical compositions and antibacterial abilities of oregano EOs (OEOs) were assessed. The results showed that OEOs from the different parts of the plant displayed only minor differences in chemical composition, whereas the yield of EOs varied considerably. Additionally, the chemical profiles of OEOs differed significantly among cultivars. The carvacrol content in the OEOs was closely related to its activity against Staphylococcus aureus; the antibacterial properties of the OEOs were further verified using carvacrol. These findings suggested that OEOs possessing high antibacterial activity may have the potential to be developed as bactericides in the food industry.