Improvement of the Ultrasound-Assisted Extraction of Polyphenols from Welsh Onion (Allium fistulosum) Leaves Using Response Surface Methodology

Efficient removal of allicin from the stalk of Allium fistulosum for dietary fiber production

The stalk of Allium fistulosum contains dietary fibers with complicated monosaccharide composition and glycosidic bond linkages, which renders it a better dietary fiber supplement. However, the unfavorable odor, majorly contributed by allicin, limits its applications. Although many physical and chemical methods have been developed to remove allicin, there is currently no comparison between their efficiencies. Here, we comprehensively compare all these methods of eliminating allicin in the Allium stalk by starting with optimization of the allicin extraction method. Results indicate that incubation of the chopped Allium stalk with water for 20 min and extraction with 75% ethanol reached a maximal extraction yield. Different methods of allicin elimination are examined, and physical removal of allicin by blanching at 100 °C reaches a maximal clearance rate of 73.3%, rendering it the most efficient and effective method eliminating allicin from the stalk of Allium fistulosum for the preparation of a totally green dietary fiber.

Gas Chromatography-Mass Spectrometry Metabolite Analysis Combined with Transcriptomics Reveals Genes Involved in Wax Biosynthesis in Allium fistulosum L

Cuticular waxes are essential for protecting plants from various environmental stresses. Allium fistulosum serves as an excellent model for investigating the regulatory mechanisms underlying cuticular wax synthesis with notable epidermal wax characteristics. A combination of gas chromatography-mass spectrometry (GC-MS) metabolite analysis and transcriptomics was used to investigate variations in metabolites and gene expression patterns between the wild type (WT) and glossy mutant type (gl2) of A. fistulosum. The WT surface had a large number of acicular and lamellar waxy crystals, whereas the leaf surface of gl2 was essentially devoid of waxy crystals. And the results revealed a significant decrease in the content of 16-hentriacontanone, the principal component of cuticular wax, in the gl2 mutant. Transcriptomic analysis revealed 3084 differentially expressed genes (DEGs) between WT and gl2. Moreover, we identified 12 genes related to fatty acid or wax synthesis. Among these, 10 DEGs were associated with positive regulation of wax synthesis, whereas 2 genes exhibited negative regulatory functions. Furthermore, two of these genes were identified as key regulators through weighted gene co-expression network analysis. Notably, the promoter region of AfisC5G01838 (AfCER1-LIKE1) exhibited a 258-bp insertion upstream of the coding region in gl2 and decreased the transcription of the AfCER1-LIKE1 gene. This study provided insights into the molecular mechanisms governing cuticular wax synthesis in A. fistulosum, laying the foundation for future breeding strategies.

Green Onion (Allium fistulosum): An Aromatic Vegetable Crop Esteemed for Food, Nutritional and Therapeutic Significance

In recent years, there has been a shift towards a greater demand for more nutritious and healthier foods, emphasizing the role of diets in human well-being. Edible Alliums, including common onions, garlic, chives and green onions, are staples in diverse cuisines worldwide and are valued specifically for their culinary versatility, distinct flavors and nutritional and medicinal properties. Green onions are widely cultivated and traded as a spicy vegetable. The mild, onion-like flavor makes the crop a pleasant addition to various dishes, serving as a staple ingredient in many world cuisines, particularly in Eastern Asian countries such as China, Japan and the Republic of Korea. The green pseudostems, leaves and non-developed bulbs of green onions are utilized in salads, stir-fries, garnishes and a myriad of culinary preparations. Additionally, green onions have a rich historical background in traditional medicine and diets, capturing the attention of chefs and the general public. The status of the crop as an important food, its culinary diversity and its nutraceutical and therapeutic value make it a subject of great interest in research. Therefore, the present review has examined the distribution, culinary, nutritional and therapeutic significance of green onions, highlighting the health benefits derived from the consumption of diets with this aromatic vegetable crop as a constituent.

Design of Experiments for Optimizing Ultrasound-Assisted Extraction of Bioactive Compounds from Plant-Based Sources

Plant-based materials are an important source of bioactive compounds (BC) with interesting industrial applications. Therefore, adequate experimental strategies for maximizing their recovery yield are required. Among all procedures for extracting BC (maceration, Soxhlet, hydro-distillation, pulsed-electric field, enzyme, microwave, high hydrostatic pressure, and supercritical fluids), the ultrasound-assisted extraction (UAE) highlighted as an advanced, cost-efficient, eco-friendly, and sustainable alternative for recovering BC (polyphenols, flavonoids, anthocyanins, and carotenoids) from plant sources with higher yields. However, the UAE efficiency is influenced by several factors, including operational variables and extraction process (frequency, amplitude, ultrasonic power, pulse cycle, type of solvent, extraction time, solvent-to-solid ratio, pH, particle size, and temperature) that exert an impact on the molecular structures of targeted molecules, leading to variations in their biological properties. In this context, a diverse design of experiments (DOEs), including full or fractional factorial, Plackett-Burman, Box-Behnken, Central composite, Taguchi, Mixture, D-optimal, and Doehlert have been investigated alone and in combination to optimize the UAE of BC from plant-based materials, using the response surface methodology and mathematical models in a simple or multi-factorial/multi-response approach. The present review summarizes the advantages and limitations of the most common DOEs investigated to optimize the UAE of bioactive compounds from plant-based materials.

Antioxidant Edible Films Based on Pear Juice and Pregelatinized Cassava Starch: Effect of the Carbohydrate Profile at Different Degrees of Pear Ripeness

Edible films based on fruit and vegetable purees combined with different food-grade biopolymeric binding agents (e.g., pectin, gelatin, starch, sodium alginate) are recognized as interesting packaging materials that benefit from the physical, mechanical, and barrier properties of biopolymers as well as the sensory and nutritional properties of purees. In the current contribution, edible antioxidant films based on pear juice and pregelatinized cassava starch were developed. In particular, the suitability of using pregelatinized cassava starch for the non-thermal production of these novel edible films was evaluated. In addition, the effects on the films' properties derived from the use of pear juice instead of the complete puree, from the content of juice used, and from the carbohydrate composition associated with the ripening of pears were all studied. The produced films were characterized in terms of their total polyphenol content, water sensitivity, and water barrier, optical, mechanical and antioxidant properties. Results showed that the use of pear juice leads to films with enhanced transparency compared with puree-based films, and that juice concentration and carbohydrate composition associated with the degree of fruit ripeness strongly govern the films' properties. Furthermore, the addition of pregelatinized cassava starch at room temperature discloses a significant and favorable impact on the cohesiveness, lightness, water resistance, and adhesiveness of the pear-juice-based films, which is mainly attributed to the effective interactions established between the starch macromolecules and the juice components.

Optimization of microwave-assisted extraction of antioxidant compounds from spring onion leaves using Box-Behnken design

Many studies have explored the extraction of bioactive compounds from different onion solid wastes, such as bulb, skin, and peel. However, onion leaves have received limited attention despite their potential as a valuable source of nutraceutical compounds. This study aimed to valorise, for the first time, the agricultural waste in the form of spring onion leaves (CN, Cipollotto Nocerino) to obtain antioxidant-rich polyphenolic extracts. A Box-Behnken design (BBD) was used to assess the impact of microwave-assisted extraction (MAE) variables (temperature, time, extraction volume, and ethanol concentration) on total polyphenol content (TPC) measured by Folin-Ciocalteu method and the antioxidant power determined by FRAP assay. Response surface methodology (RSM) was applied, and regression equations, analysis of variance, and 3D response curves were developed. Our results highlighted that the TPC values range from 0.76 to 1.43 mg GAE g-1 dw, while the FRAP values range from 8.25 to 14.80 mmol Fe(II)E g-1 dw. The optimal extraction conditions predicted by the model were 60 °C, 22 min, ethanol concentration 51% (v/v), and solvent volume 11 mL. These conditions resulted in TPC and FRAP values of 1.35 mg GAE g-1 dw and 14.02 mmol Fe(II)E g-1 dw, respectively. Furthermore, the extract obtained under optimized conditions was characterized by UHPLC-ESI-Orbitrap-MS analysis. LC/MS-MS platform allowed us to tentatively identify various compounds belonging to the class of flavonoids, saponins, fatty acids, and lipids. Finally, the ability of CN optimal extract to inhibit the intracellular reactive oxygen species (ROS) release in a hepatocarcinoma cell line using an H2O2-induced oxidative stress model, was evaluated. The results highlighted the potential of CN extract as a valuable source of polyphenols with significant antioxidant properties, suitable for various applications in the food and pharmaceutical industries.

Functional Perspective of Leeks: Active Components, Health Benefits and Action Mechanisms

Leek (Allium fistulosum L.), a common and widely used food ingredient, is a traditional medicine used in Asia to treat a variety of diseases. Leeks contain a variety of bioactive substances, including sulfur compounds, dietary fiber, steroid compounds and flavonoid compounds. Many studies have shown that these active ingredients produce the following effects: promotion of blood circulation, lowering of cholesterol, relief of fatigue, anti-inflammation, anti-bacteria, regulation of cell metabolism, anti-cancer, anti-oxidation, and the lowering of fat and blood sugar levels. In this paper, the main bioactive components and biological functions of leeks were systemically reviewed, and the action mechanisms of bioactive components were discussed. As a common food, the health benefits of leeks are not well known, and there is no systematic summary of leek investigations. In light of this, it is valuable to review the recent progress and provide reference to investigators in the field, which will promote future applications and investigations of leeks.

Modeling and Optimization of Ultrasound-Assisted Extraction of Bioactive Compounds from Allium sativum Leaves Using Response Surface Methodology and Artificial Neural Network Coupled with Genetic Algorithm

This study explains the effect of ultrasound on the extraction of the bioactive compounds from garlic (Allium sativum L.) leaf powder. The experiment was carried out by varying the ultrasound amplitude (30-60%), treatment time (5-15 min), and ethanol concentration (40-60%) required to obtain the maximum extraction yield of total phenol content (TPC), total flavonoid content (TFC), and antioxidant activity. Rotatable central composite design (RCCD) provided experimental parameter combinations in the ultrasound-assisted extraction (UAE) of garlic leaf powder. The values of extraction yield, TPC, TFC, and antioxidant activity for the optimized condition of RSM were obtained at 53% amplitude, 13 min of treatment time, and 50% ethanol concentration. The values of the target compounds predicted at this optimized condition from RSM were 32.2% extraction yield, 9.9 mg GAE/g TPC, 6.8 mg QE/g TFC, and 58% antioxidant activity. The ANN-GA optimized condition for the leaf extracts was obtained at 60% amplitude, 13 min treatment time, and 53% ethanol concentration. The predicted values of optimized condition obtained by ANN-GA were recorded as 32.1738% extraction yield and 9.8661 mg GAE/g, 6.8398 mg QE/g, and 58.5527% for TPC, TFC, and antioxidant activity, respectively. The matured leaves of garlic, if not harvested during its cultivation, often go waste despite being rich in antioxidants and phenolic compounds. With the increased demand for the production of value-added products, the extraction of the bioactive compounds from garlic leaves can resolve waste management and potential health issues without affecting the crop yield through the process for high-end use in value addition.

Establishment of a Sonotrode Ultrasound-Assisted Extraction of Phenolic Compounds from Apple Pomace

Apple pomace is the main by-product from apple processing in the juice industry and is considered a source of polyphenols with several health bioactivities. Thus, this research focuses on the establishment of the ultrasound-assisted extraction of total phenolic compounds, focusing on phloretin and phloridzin, with high antioxidant activity from apple pomace, using a sonotrode. We used a Box-Behnken design of 15 experiments with 3 independent factors (ethanol (%), time (min) and amplitude (%)). The responses evaluated were the sum of phenolic compounds, phloretin and phloridzin measured by HPLC-MS-ESI-TOF, and antioxidant activity measured by DPPH, ABTS and FRAP. The validity of the model was confirmed by ANOVA. Further, it was carried out using a comparison between different apple pomaces with or without seeds extracted by the optimal conditions. Phloretin and phloridzin accounted for 7 to 32% of the total phenolic compounds in the apple pomaces. Among all the apple pomace analyzed, that of the variety Gala had the highest phenolic content and antioxidant activity. The presence of the cyanogenic compound amygdalin was detected in apple pomaces that contained seeds accompanied with a higher content of phloretin and phloridzin but a lower content of flavan-3-ols.