From Foxtail Millet Husk (Waste) to Bioactive Phenolic Extracts Using Deep Eutectic Solvent Extraction and Evaluation of Antioxidant, Acetylcholinesterase, and α-Glucosidase Inhibitory Activities

Unraveling the nutritional potential of millet by-products through extraction of high value compounds for the development of novel food products

Millets are drought-resistant crops that generate significant amount of by-products (bran, husk, stalk etc.) during harvesting and processing. These by-products are storehouse of nutrients and high value compounds including polyphenols, dietary fiber, proteins etc. However, these by-products remain underutilized and generally discarded, burned or used as feedstock causing adverse impact on the environment and human health in addition to loss of valuable nutrients. Therefore, the valorization of millet by-products offers sustainable approach to enhance food product innovation while reducing agricultural waste. Green extraction techniques can be employed to recover antioxidants, phenolics, and bioactive peptides from these by-products. The incorporation of these ingredients into food products can significantly improve the nutritional profile, functional characteristics, like antioxidant, prebiotic, anti-diabetic, and anticarcinogenic properties. The review highlights the feasibility of upcycling millet by-products into high-value components, which can address the growing demand for health-oriented food products contributing towards food security, sustainability and circular economy.

Biomass-Derived Activated Porous Carbon from Foxtail Millet Husk to Utilizing High-Performance Symmetric Supercapacitor Applications

This study successfully demonstrates the synthesis of foxtail millet carbon-activated (FMCA) materials using a two-step carbonization process from foxtail millet husk (FMH). The pre-carbonized biomass-derived millet husk was chemically activated with KOH at 500 °C and subsequently carbonized in an inert argon atmosphere at 800 °C in a tubular furnace. XRD analysis revealed a diffraction peak at 2θ = 23.67°, corresponding to the (002) plane, indicating the presence of graphitic structures. The Raman analysis of FMCA materials showed an intensity ratio (IG/ID) of 1.13, signifying enhanced graphitic ordering and structural stability. The as-prepared FMC and FMCA electrode materials demonstrate efficient charge storage electrochemical symmetric devices. Electrochemical analysis revealed the charge-discharge curves and a specific capacitance of Csp (FMC//FMC) 55.47 F/g and (FMCA//FMCA) 82.94 F/g at 0.5 A/g. Additionally, the FMCA//FMCA symmetric device exhibits superior performance with a higher capacity retention of 94.89% over 5000 cycles. The results confirm the suitability of FMCA for energy storage applications, particularly in electrochemical double-layer capacitors (EDLCs), making it a promising material for next-generation supercapacitors.

A comparative evaluation of the composition and antioxidant activity of free and bound polyphenols in sugarcane tips

The sugarcane tip is abundant in phenolic compounds. Previous studies have concentrated on the effects of free polyphenols, while bound polyphenols were overlooked. In this study, the content of bound polyphenols (SPB) (31.9 ± 0.9 mg GAE/g DW) was significantly higher than free polyphenols (SPF) (3.4 ± 0.1 mg GAE/g DW). A total of 44 free and 31 bound phenolics were identified by the UPLC-EIS-QTOF-MS/MS. Moreover, the antioxidant activity of SPB was more pronounced, as evidenced by its higher ABTS+ and DPPH scavenging rates than SPF, which was attributed to the higher tannin content. Furthermore, at all tested concentrations (100 and 200 μg/mL), SPB significantly enhanced the survival and antioxidant enzyme activity of Caenorhabditis elegans (C. elegans), while concurrently reducing ROS levels. High concentrations of SPB even exhibited antioxidant activity comparable to Vitamin C (Vc). The collective findings strongly indicate that SPB holds great potential as an effective antioxidant.

Nutrient and metabolite characteristics of the husk, bran and millet isolated from the foxtail millet (Setaria italica L.) during polishing

The utilization of byproducts from foxtail millet polishing can reduce food loss and waste. Thus, it is necessary to know the chemical compounds from the millet and the segregation of the layers. The nutrients including minerals were compared among the husk, bran, and millet, and a LC-MS metabolomics analysis was also performed among them. The results showed that the protein, crude fat and 4 fatty acids, seven minerals, the nitrogen-containing compounds and phenolic acids were at much higher levels in the bran part than the husk and millet, whereas the husk only contained higher levels of dietary fibre, and some minerals. The millet section, as the edible part, contained the lowest level of chemical constituents. It illustrated that the bran part contained more functional and nutritional components than the millet and husk part. Therefore, the bran of the foxtail millet should be a food resources instead of wasting.

Optimization of Germination Conditions for Enriched γ-Aminobutyric Acid and Phenolic Compounds of Foxtail Millet Sprouts by Response Surface Methodology

The optimum germination conditions for foxtail millet sprouts enriched with γ-aminobutyric acid (GABA) and antioxidant polyphenols were investigated. From single-factor experimental results, both the GABA level and total phenolic content (TPC) were more significantly affected by soaking temperature and time, and concentration of sucrose culture solution. Response surface methodology (RSE) was used to optimize the germination conditions of foxtail millet sprouts, where the interaction between soaking temperature and sucrose concentration exhibited a significant (p < 0.05) effect on TPC, and the interaction between soaking time and sucrose concentration displayed a significant (p < 0.05) effect on GABA content. The optimal germination conditions for TPC and GABA enrichment of foxtail millet sprouts were soaking at 31 °C for 4.5 h and germinating at 35 °C with 4.5 g/L sucrose solution for 5 days. Under the optimized conditions, the TPC and GABA content of foxtail millet sprouts were 926.53 milligrams of ferulic acid equivalents per 100 g dry weight (mg FAE/100 g DW) and 259.13 mg/kg, separately, with less difference from the predicted values of 929.44 mg FAE/100 g DW and 263.60 mg/kg, respectively. Collectively, all the individual phenolic compounds increased significantly (p < 0.05) by optimization, except for cis-p-coumaric acid and cis-ferulic acid in bound. The results provide a practical technology for suitable germination conditions to improve the health components of foxtail millet sprouts and increase their added value.

Advances in the novel and green-assisted techniques for extraction of bioactive compounds from millets: A comprehensive review

Millets are rich in nutritional and bioactive compounds, including polyphenols and flavonoids, and have the potential to combat malnutrition and various diseases. However, extracting these bioactive compounds can be challenging, as conventional methods are energy-intensive and can lead to thermal degradation. Green-assisted techniques have emerged as promising methods for sustainable and efficient extraction. This review explores recent trends in employing green-assisted techniques for extracting bioactive compounds from millets, and potential applications in the food and pharmaceutical industries. The objective is to evaluate and comprehend the parameters involved in different extraction methods, including energy efficiency, extraction yield, and the preservation of compound quality. The potential synergies achieved by integrating multiple extraction methods, and optimizing extraction efficiency for millet applications are also discussed. Among several, Ultrasound and Microwave-assisted extraction stand out for their rapidity, although there is a need for further research in the context of minor millets. Enzyme-assisted extraction, with its low energy input and ability to handle complex matrices, holds significant potential. Pulsed electric field-assisted extraction, despite being a non-thermal approach, requires further optimization for millet-specific applications, are few highlights. The review emphasizes the importance of considering specific compound characteristics, extraction efficiency, purity requirements, and operational costs when selecting an ideal technique. Ongoing research aims to optimize novel extraction processes for millets and their byproducts, offering promising applications in the development of millet-based nutraceutical food products. Therefore, the current study benefits researchers and industries to advance extraction research and develop efficient, sustainable, and scalable techniques to extract bioactive compounds from millets.

A Comprehensive Review on Deep Eutectic Solvents and Its Use to Extract Bioactive Compounds of Pharmaceutical Interest

The extraction of bioactive compounds of pharmaceutical interest from natural sources has been significantly explored in recent decades. However, the extraction techniques used were not very efficient in terms of time and energy consumption; additionally, the solvents used for the extraction were harmful for the environment. To improve the environmental impact of the extractions and at the same time increase the extraction yields, several new extraction techniques were developed. Among the most used ones are ultrasound-assisted extraction and microwave-assisted extraction. These extraction techniques increased the yield and selectivity of the extraction in a smaller amount of time with a decrease in energy consumption. Nevertheless, a high volume of organic solvents was still used for the extraction, causing a subsequent environmental problem. Neoteric solvents appeared as green alternatives to organic solvents. Among the neoteric solvents, deep eutectic solvents were evidenced to be one of the best alternatives to organic solvents due to their intrinsic characteristics. These solvents are considered green solvents because they are made up of natural compounds such as sugars, amino acids, and carboxylic acids having low toxicity and high degradability. In addition, they are simple to prepare, with an atomic economy of 100%, with attractive physicochemical properties. Furthermore, the huge number of compounds that can be used to synthesize these solvents make them very useful in the extraction of bioactive compounds since they can be tailored to be selective towards a specific component or class of components. The main aim of this paper is to give a comprehensive review which describes the main properties, characteristics, and production methods of deep eutectic solvents as well as its application to extract from natural sources bioactive compounds with pharmaceutical interest. Additionally, an overview of the more recent and sustainable extraction techniques is also given.

Green Extraction of Hodgsonia heteroclita Oilseed Cake Powder to Obtain Optimal Antioxidants and Health Benefits

Most biowaste produced by domestic food preparation and food processing has no value, is difficult to manage, and is detrimental to the environment. Oil extraction from Hodgsonia heteroclita seeds produces large amounts of oilseed cake powder (OCP) as biowaste. The extraction of residual phytochemicals using simple and eco-friendly methods can increase the economic utility of OCP. This study optimized the extraction process for Hodgsonia heteroclita OCP using a Box-Behnken design and response surface methodology. The optimized extraction condition was 30 °C for 5 h in 50% (v/v) ethanol, giving a total phenolic content (TPC) of 414.23 mg of gallic acid equivalent/100 g dry weight (DW). Phytochemical profiles of OCP using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ECI-MS/MS) identified 4-hydroxybenzoic acid and ferulic acid as the major compounds. Antioxidant activities and enzyme inhibitory activities toward the major enzymes involved in obesity (lipase), diabetes (α-amylase, α-glucosidase, and dipeptidyl peptidase IV (DPP IV)), Alzheimer's disease (acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase-1 (BACE-1)), hypertension (angiotensin-converting enzyme, ACE), and genotoxicity were also investigated. Results showed that H. heteroclita OCP possessed antioxidant activity and potential inhibitory activities against BACE-1 and ACE, while also being genome-safe. A simple extraction method for H. heteroclita OCP was developed, demonstrating the enhanced value of its phytochemical and health-promoting qualities.