Extraction of Essential Oil from River Tea Tree (Melaleuca bracteata F. Muell.): Antioxidant and Antimicrobial Properties

Antifungal potential of essential oils from different botanical sources against Penicillium digitatum: chemical composition and antifungal mechanisms of action by direct contact and volatile

Fungal deterioration is a recurring problem in citrus fruits, and the search for natural preservatives has been widely publicised. Therefore, the in vitro antifungal activity of clove, white thyme, tea tree, Eucalyptus citriodora, Eucalyptus staigeriana, green mandarin, sicilian lemon, sweet orange, and bergamot essential oils (EO's) was evaluated against the mycelial growth of Penicillium digitatum isolated from contaminated citrus fruits, by direct contact and volatiles action. In addition, the chemical composition and volatile compounds of the EO's were evaluated by gas chromatography. Clove, white thyme, and Eucalyptus citriodora EO's inhibited 100% of the mycelial growth of P. digitatum by direct contact and volatile action at concentrations ≤ 2 µL/mL. On the other hand, EO's from citrus sources could not inhibit 100% of mycelial growth by any mechanism of action. Thus, the clove, thyme, and Eucalyptus citriodora EO's are promising for developing new ecologically correct products for controlling phytopathogens in citrus fruits.

Antimicrobial Activity against Cronobacter of Plant Extracts and Essential Oils in a Matrix of Bacterial Cellulose

Bacterial cellulose (BC) is a biodegradable polymer resembling paper after being dried. It finds a growing number of applications in many branches of industry and in medicine. In the present study, BC was produced after Gluconacetobacter hansenii ATCC 23769 strain culture and used as a matrix for plant extracts (tulsi, brahmi, lemon, blackberry, nettle root, and nettle leave) and essential oils (cinnamon, sage, clove, mint, thyme, lemongrass, rosemary, lemon, anise, tea tree, lime, grapefruit, and tangerine), and the antimicrobial properties of these biomaterials was determined. The growth-inhibiting effects of plant extracts and essential oils combined with BC were analyzed against five Cronobacter species isolated from food matrix and two reference strains from the ATCC (513229 and 29544). Additional analyses were conducted for BC water activity and for its capability to absorb biologically active plant compounds. The cellulose matrix with a 50% extract from brahmi was found to effectively inhibit the growth of the selected Cronobacter strains. The other plant water extracts did not show any antimicrobial activity against the tested strains. It was demonstrated that BC soaked with thyme essential oil was characterized with the strongest antimicrobial activity in comparison to the other tested EOs. These study results indicate the feasibility of deploying BC impregnated with natural plant components as an active and environmentally-friendly packaging material.

Advances in detecting fruit aroma compounds by combining chromatography and spectrometry

Fruit aroma is produced by volatile compounds, which can significantly enhance fruit flavor. These compounds are highly complex and have remarkable pharmacological effects. The synthesis, concentration, type, and quantity of fruit aroma substances are affected by various factors, both abiotic and biotic. To fully understand the aroma substances of various fruits and their influencing factors, detection technology can be used. Many methods exist for detecting aroma compounds, and approaches combining multiple instruments are widely used. This review describes and compares each detection technology and discusses the potential use of combined technologies to provide a comprehensive understanding of fruit aroma compounds and the factors influencing their synthesis. These results can inform the development and utilization of fruit aroma substances. © 2023 Society of Chemical Industry.

The Role of MbEGS1 and MbEGS2 in Methyleugenol Biosynthesis by Melaleuca bracteata

Many aromatic plant volatile compounds contain methyleugenol, which is an attractant for insect pollination and has antibacterial, antioxidant, and other properties. The essential oil of Melaleuca bracteata leaves contains 90.46% methyleugenol, which is an ideal material for studying the biosynthetic pathway of methyleugenol. Eugenol synthase (EGS) is one of the key enzymes involved in the synthesis of methyleugenol. We recently reported two eugenol synthase genes (MbEGS1 and MbEGS2) present in M. bracteata, where MbEGS1 and MbEGS2 were mainly expressed in flowers, followed by leaves, and had the lowest expression levels in stems. In this study, the functions of MbEGS1 and MbEGS2 in the biosynthesis of methyleugenol were investigated using transient gene expression technology and virus-induced gene silencing (VIGS) technology in M. bracteata. Here, in the MbEGSs genes overexpression group, the transcription levels of the MbEGS1 gene and MbEGS2 gene were increased 13.46 times and 12.47 times, respectively, while the methyleugenol levels increased 18.68% and 16.48%. We further verified the function of the MbEGSs genes by using VIGS, as the transcript levels of the MbEGS1 and MbEGS2 genes were downregulated by 79.48% and 90.35%, respectively, and the methyleugenol content in M. bracteata decreased by 28.04% and 19.45%, respectively. The results indicated that the MbEGS1 and MbEGS2 genes were involved in the biosynthesis of methyleugenol, and the transcript levels of the MbEGS1 and MbEGS2 genes correlated with the methyleugenol content in M. bracteata.

Tea Tree Oil Nanoemulsion-Based Hydrogel Vehicle for Enhancing Topical Delivery of Neomycin

The present investigation aims to improve the antimicrobial influence of certain antibacterial drugs, namely, neomycin (NEO), exploiting the benefits of natural oils such as tea tree oil (TTO). Therefore, a distinctive nanolipid formulation, namely, a nanoemulsion (NE), was developed using a Central Composite Factorial Design (CCD) approach depending on the amount of TTO and tween 80 as surfactant. The optimized NEO-NE formula exhibiting minimum globular size and maximum in vitro release was selected. For efficient topical delivery, NEO-NE was incorporated into a pre-formulated hydrogel. The developed NEO-NE-hydrogel was characterized by its physical characteristics such as pH, viscosity, and spreadability. Next, it was tested for stability under different conditions for 3 months. Ultimately, an irritation test was conducted followed by an antibacterial examination. The preparation demonstrated acceptable properties to be successfully applied topically. It showed non-significant changes in stability in both conditions up to 3 months storage when compared to a fresh preparation. It exhibited no irritation when applied on hairless animal skin. Finally, TTO revealed a good inhibition for the bacterial growth that could improve the influence of NEO antibacterial activity, indicating the efficiency of NE containing NEO prepared with TTO to be a promising antibacterial nanocarrier.

The Multifaceted Nature of Food and Nutrition Insecurity around the World and Foodservice Business

Food security is more than a basic requirement for survival; it is a human right that has implications for global safety, economic strength, security, and sustainability [...]

Biosynthetic pathways of triterpenoids and strategies to improve their Biosynthetic Efficiency

"Triterpenoids" can be considered natural products derived from the cyclization of squalene, yielding 3-deoxytriterpenes (hydrocarbons) or 3-hydroxytriterpenes. Triterpenoids are metabolites of these two classes of triterpenes, produced by the functionalization of their carbon skeleton. They can be categorized into different groups based on their structural formula/design. Triterpenoids are an important group of compounds that are widely used in the fields of pharmacology, food, and industrial biotechnology. However, inadequate synthetic methods and insufficient knowledge of the biosynthesis of triterpenoids, such as their structure, enzymatic activity, and the methods used to produce pure and active triterpenoids, are key problems that limit the production of these active metabolites. Here, we summarize the derivatives, pharmaceutical properties, and biosynthetic pathways of triterpenoids and review the enzymes involved in their biosynthetic pathway. Furthermore, we concluded the screening methods, identified the genes involved in the pathways, and highlighted the appropriate strategies used to enhance their biosynthetic production to facilitate the commercial process of triterpenoids through the synthetic biology method.

River Tea Tree Oil: Composition, Antimicrobial and Antioxidant Activities, and Potential Applications in Agriculture

Melaleuca is one of the genera of the Myrtaceae family enriched in tea tree oil (TTO). Tea tree oils of Melaleuca bracteata and Melaleuca alternifolia are of prime importance and have antioxidant and antimicrobial properties. Terpinen-4-ol and 1-8 cineole are major constituents of M. alternifolia oil. The percentages of the compounds in the oils can slightly vary according to the region of plant harvest, the distillation technique, or the part of the plant used for oil extraction. TTO has a bactericidal effect against various bacterial species such as Bacillus cereus, B. subtilis, E. coli, Pseudomonas putida, and S. aureus. Several reports proved that this essential oil is also effective against fungal strains of Fusarium, Aspergillus, and Candida species. It also has antioxidant properties such as radical scavenging activity and reducing power. The antioxidant properties of TTO at a concentration of 30 mM were observed to be greater than those of butylated hydroxytoluene (BHT), commonly used as a synthetic antioxidant. TTO is also an effective organic fungicide, herbicide, and insecticide for use in the agriculture sector. Postharvest application of the oil has been found efficient on sweet basil, citrus, and strawberry. It is concluded that tea tree oil has the potential to be used in the food, agriculture, and pharmaceutical industries as a natural antimicrobial and preservative agent. This review provides comprehensive information regarding the antioxidant and antimicrobial activities of tea tree oil and its potential applications in agriculture.