Extraction and bioconversion of kaempferol metabolites from cauliflower outer leaves through fungal fermentation

An integrative multi-omics approach reveals metabolic mechanism of flavonoids during anaerobic fermentation of de'ang pickled tea

Anaerobic fermentation (AF) is critical process for Yunnan De'ang pickled tea production. Therefore, widely targeted metabolomics and metagenomics were integrated to reveal the AF mechanism. Lactic acid bacteria (LAB) (e.g. Lactiplantibacillus plantarum, Lactobacillus vaccinostercus and Lactobacillus paracollinoides) and yeasts like Candida metapsilosis and Cyberlindnera fabianii dominated in the AF. Based on bacterial community succession and metabolites variation, the whole AF processes were divided into two phases, i.e., before and after four months. A total of 327 characteristic metabolites (VIP >1.0, P < 0.05, and FC > 1.50 or < 0.67) were selected from the AF. Besides amino acids increase, LAB and yeasts also promoted non-galloylated catechins, and several simple flavones/flavonols, flavanones/flavanonols and methoxy flavones/flavonols accumulations along with galloylated catechins, flavonol/flavone glycosides and anthocyanins decrease during the AF. This study would improve the understanding about AF mechanism of tea-leaves from the perspectives of flavonoids metabolism and microbial community succession.

Recent advances in methods of extraction, pre-concentration, purification, identification, and quantification of kaempferol

As a naturally widely-occurring dietary, cosmetic, and therapeutic flavonoid, kaempferol has gained much consideration for its nutritional and pharmaceutical properties in recent years. Although there have been performed a high number of studies associated with different aspects of kaempferol's analytical investigations, the lack of a comprehensive summary of the various methods and other plant sources that have been reported for this compound is being felt, especially for many biological applications. This study, aimed to provide a detailed compilation consisting of sources (plant species) and analytical information that was precisely related to the natural flavonoid (kaempferol). There is a trend in analytical research that supports the application of modern eco-friendly instruments and methods. In conclusion, ultrasound-assisted extraction (UAE) is the most general advanced method used widely today for the extraction of kaempferol. During recent years, there is an increasing tendency towards the identification of kaempferol by different methods.

Effect of Lentinus sajor-caju on the chemical composition and antioxidant activity of highland barley straw under solid-state fermentation

Introduction

The efficient utilization of straw resources as animal feed has gained considerable attention. The objective of this study was to evaluate whether Lentinus sajor-caju treatment alters the chemical composition and antioxidant activity of highland barley straw and enhances its functional value as a ruminant feed.

Methods

The chemical composition, antioxidant capacity, and metabolomic profile of highland barley straw were determined after 21 days of solid-state fermentation with L. sajor-caju at 25°C. The differential metabolites between fermented and unfermented highland barley straw were identified by LC-MS and the relationship between the identified metabolites and antioxidant capacity was elucidated.

Results

The results showed that, compared with untreated highland barley straw, the crude protein and ether extract contents were higher (51.55 and 76.43%, respectively) in highland barley straw after 21 days of incubation with L. sajor-caju, whereas the hemicellulose, cellulose, and acid detergent lignin contents were lower (2.48, 25.08, and 45%, respectively). The total antioxidant capacity was significantly higher in L. sajor-caju-treated than in untreated highland barley straw. In total, 600 differential metabolites (301 upregulated and 299 downregulated) were identified between L. sajor-caju-fermented and unfermented highland barley straw. Correlation analysis results showed that Fe2+ scavenging and total phenolic content were strongly correlated with total antioxidant capacity. Meanwhile, the differential flavonoid metabolites between fermented and unfermented highland barley straw were primarily associated with antioxidant activity, with kaempferol 3-xylosylglucoside, isoginkgetin, and rhoifolin being the most representative.

Conclusion

Thus, this study demonstrates that L. sajor-caju could enhance the functional value of highland barley straw, showing the potential of L. sajor-caju for improving the utilization of agricultural straws in ruminants.

Optimising the recovery of phenolic compounds and antioxidant activity from orange peels through solid-state fermentation

It is widely recognised that orange peels contain a considerable quantity of phenolics, primarily in the form of glycosides. The process of fermentation holds potential as a viable method for extracting phenolic compounds and facilitating their biotransformation into novel metabolites. The aim of this study was to assess the enhanced release of phenolic compounds through the process of solid-state fermentation of orange peels using microorganisms. Following a 6-day incubation period, the methanol extract obtained from the sample fermented with starter Banh men exhibited the highest concentration of total phenolic compounds (17.57 ± 0.34 mg GAE/g DW) and demonstrated the most significant DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (55.03%). The Reverse Phase High Performance Liquid Chromatography (RP-HPLC) analysis revealed that the predominant phenolic compounds in all fermented samples were flavonoid aglycones, specifically naringenin, hesperetin, and nobiletin. Conversely, in the unfermented orange peels, the major compound observed was the glycoside derivative hesperidin.

The Valorization of Wastes and Byproducts from Cruciferous Vegetables: A Review on the Potential Utilization of Cabbage, Cauliflower, and Broccoli Byproducts

The management of vegetable waste and byproducts is a global challenge in the agricultural industry. As a commonly consumed vegetable crop, cruciferous vegetables marked higher amounts of wastage during their supply chain processes, with a significant contribution from cabbage, cauliflower, and broccoli. Therefore, the sustainable and resource-efficient utilization of discarded materials is crucial. This review explores potential applications of cruciferous vegetable waste and byproducts, spotlighting cabbage, cauliflower, and broccoli in food, medicinal, and other industries. Their significance of being utilized in value-added applications is addressed, emphasizing important biomolecules, technologies involved in the valorization process, and future aspects of practical applications. Cabbage, cauliflower, and broccoli generate waste and low-processing byproducts, including leaves, stems, stalks, and rot. Most of them contain high-value biomolecules, including bioactive proteins and phytochemicals, glucosinolates, flavonoids, anthocyanins, carotenoids, and tocopherols. Interestingly, isothiocyanates, derived from glucosinolates, exhibit strong anti-inflammatory and anticancer activity through various interactions with cellular molecules and the modulation of key signaling pathways in cells. Therefore, these cruciferous-based residues can be valorized efficiently through various innovative extraction and biotransformation techniques, as well as employing different biorefinery approaches. This not only minimizes environmental impact but also contributes to the development of high-value-added products for food, medicinal, and other related industries.

Natural Pigments Production and Their Application in Food, Health and Other Industries

In addition to fulfilling their function of giving color, many natural pigments are known as interesting bioactive compounds with potential health benefits. These compounds have various applications. In recent times, in the food industry, there has been a spread of natural pigment application in many fields, such as pharmacology and toxicology, in the textile and printing industry and in the dairy and fish industry, with almost all major natural pigment classes being used in at least one sector of the food industry. In this scenario, the cost-effective benefits for the industry will be welcome, but they will be obscured by the benefits for people. Obtaining easily usable, non-toxic, eco-sustainable, cheap and biodegradable pigments represents the future in which researchers should invest.

Fermentation transforms the phenolic profiles and bioactivities of plant-based foods

Phenolics are a group of compounds derived from plants that have displayed potent biological activities and health-promoting effects. Fermentation is one of the most conventional but still prevalent bioprocessing methods in the food industry, with the potential to increase phenolic content and enhance its nutritive value. This review details the biotransformation of different classes of phenolics (hydroxycinnamic and hydroxybenzoic acids, flavonoids, tannins, stilbenoids, lignans, alkylresorcinols) by various microorganisms (lactic acid bacteria, yeast, filamentous fungi) throughout the fermentation process in plant-based foods. Several researchers have commenced the use of metabolic engineering, as in recombinant Saccharomyces cerevisiae yeast and Escherichia coli, to enhance the production of this transformation. The impact of phenolics on the metabolism of microorganisms and fermentation process, although complex, is reviewed for the first time. Moreover, this paper highlights the general effect of fermentation on the food's phenolic content, and its bioaccessibility, bioavailability and bioactivities including antioxidant capacity, anti-cancer, anti-diabetic, anti-inflammation, anti-obesity properties. Phenolics of different classes are converted into compounds that are often more bioactive than the parent compounds, and fermentation generally leads to a higher phenolic content and antioxidant activity in most studies. However, biotransformation of several phenolic classes is less studied due to its low concentration and apparent insignificance to the food system. Therefore, there is potential for application of metabolic engineering to further enhance the content of different phenolic classes and bioactivities in food.

Valorization of fruits and vegetable wastes and by-products to produce natural pigments

Synthetic pigments from petrochemicals have been extensively used in a wide range of food products. However, these pigments have adverse effects on human health that has rendered it obligatory to the scientific community in order to explore for much safer, natural, and eco-friendly pigments. In this regard, exploiting the potential of agri-food wastes presumes importance, extracted mainly by employing green processing and extraction technologies. Of late, pigments market size is growing rapidly owing to their extensive uses. Hence, there is a need for sustainable production of pigments from renewable bioresources. Valorization of vegetal wastes (fruits and vegetables) and their by-products (e.g. peels, seeds or pomace) can meet the demands of natural pigment production at the industrial levels for potential food, pharmaceuticals, and cosmeceuticals applications. These wastes/by-products are a rich source of natural pigments such as: anthocyanins, betalains, carotenoids, and chlorophylls. It is envisaged that these natural pigments can contribute significantly to the development of functional foods as well as impart rich biotherapeutic potential. With a sustainability approach, we have critically reviewed vital research information and developments made on natural pigments from vegetal wastes, greener extraction and processing technologies, encapsulation techniques and potential bioactivities. Designed with an eco-friendly approach, it is expected that this review will benefit not only the concerned industries but also be of use to health-conscious consumers.

Adsorption of Lead (II) from Aqueous Solution with High Efficiency by Hydrothermal Biochar Derived from Honey

A novel natural honey hydrothermal biochar (HHTB) was prepared using natural honey as raw material. The as-prepared adsorbent was applied to adsorb Pb²⁺ from aqueous solution and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy to investigate the structure and morphology change of the adsorbent before and after Pb²⁺ adsorption. The influence of the pH, initial Pb²⁺ concentration, temperature, and contact time on the adsorption of Pb²⁺ was systematically investigated. The results revealed that the adsorption capacity for Pb²⁺ is up to 133.2 mg·g⁻¹ at initial pH of 5.0 and adsorption temperature of 298 K. Meanwhile, the adsorption of Pb²⁺ on HHTB can be well fitted by the pseudo-second-order model and Langmuir isotherm model. The adsorbent had great selectivity for Pb²⁺ from the aqueous solution containing coexisting ions including Cd²⁺, Co²⁺, Cr³⁺, Cu²⁺, Ni²⁺ and Zn²⁺. Furthermore, the adsorption of Pb²⁺ on HHTB was attributed to complexation coordination, where it involved hydroxyl and carboxylic groups on HHTB in the process of adsorption of Pb²⁺.

Conventional and Emerging Extraction Processes of Flavonoids

Flavonoids are a group of plant constituents called phenolic compounds and correspond to the nonenergy part of the human diet. Flavonoids are found in vegetables, seeds, fruits, and beverages such as wine and beer. Over 7000 flavonoids have been identified and they have been considered substances with a beneficial action on human health, particularly of multiple positive effects because of their antioxidant and free radical scavenging action. Although several studies indicate that some flavonoids have provident actions, they occur only at high doses, confirming in most investigations the existence of anti-inflammatory effects, antiviral or anti-allergic, and their protective role against cardiovascular disease, cancer, and various pathologies. Flavonoids are generally removed by chemical methods using solvents and traditional processes, which besides being expensive, involve long periods of time and affect the bioactivity of such compounds. Recently, efforts to develop biotechnological strategies to reduce or eliminate the use of toxic solvents have been reported, reducing processing time and maintaining the bioactivity of the compounds. In this paper, we review, analyze, and discuss methodologies for biotechnological recovery/extraction of flavonoids from agro-industrial residues, describing the advances and challenges in the topic.

Bioactives From Agri-Food Wastes: Present Insights and Future Challenges

Sustainable utilization of agri-food wastes and by-products for producing value-added products (for cosmetic, pharmaceutical or food industrial applications) provides an opportunity for earning additional income for the dependent industrial sector. Besides, effective valorisation of wastes/by-products can efficiently help in reducing environmental stress by decreasing unwarranted pollution. The major focus of this review is to provide comprehensive information on valorisation of agri-food wastes and by-products with focus laid on bioactive compounds and bioactivity. The review covers the bioactives identified from wastes and by-products of plants (fruits, exotic fruits, vegetables and seeds), animals (dairy and meat) and marine (fish, shellfish seaweeds) resources. Further, insights on the present status and future challenges of sustainably utilizing agri-food wastes/by-products for value addition will be highlighted.

Bioconversion of Kaempferol and Quercetin Glucosides from Plant Sources Using Rhizopus spp

Fermentation with filamentous fungi is known for the ability to convert bioactive compounds. The aim of this research was to investigate the metabolism of glycosidic derivatives of kaempferol and quercetin during fungal fermentation of extracts from cauliflower outer leaves and onion by Rhizopus oryzae and R. azygosporus. The highest release of kaempferol and quercetin was observed after 2 days and 1 day of fermentation with R. oryzae, respectively. It was proposed that glycosidic compounds were initially deglycosylated to form kaempferol-3-glucoside and quercetin-3-glucoside and then further metabolized into their aglycones. Clear differences in conversion efficiency towards the aglycones were observed between the two Rhizopus strains. Although both flavonoids only differ in one hydroxyl group, the metabolism of the glycosides towards their respective aglycones, kaempferol or quercetin, was different. It is concluded that the fermentation with R. oryzae and R. azygosporus could be considered as a way to produce kaempferol and quercetin aglycone from their glycosidic derivatives.

Systematic metabolic profiling and bioactivity assays for bioconversion of Aceraceae family

Plants are an important and inexhaustible source of bioactive molecules in food, medicine, agriculture, and industry. In this study, we performed systematic liquid chromatography-mass spectrometry (LC-MS)-based metabolic profiling coupled with antioxidant assays for indigenous plant family extracts. Partial least-squares discriminant analysis of LC-MS datasets for the extracts of 34 plant species belonging to the families Aceraceae, Asteraceae, and Rosaceae showed that these species were clustered according to their respective phylogenies. In particular, seven Aceraceae species were clearly demarcated with higher average antioxidant activities, rationalizing their application for bioconversion studies. On the basis of further evaluation of the interspecies variability of metabolic profiles and antioxidant activities among Aceraceae family plants, we found that Acer tataricum (TA) extracts were clearly distinguished from those of other species, with a higher relative abundance of tannin derivatives. Further, we detected a strong positive correlation between most tannin derivatives and the observed higher antioxidant activities. Following Aspergillus oryzae-mediated fermentative bioconversion of Acer plant extracts, we observed a time-correlated (0-8 days) linear increase in antioxidant phenotypes for all species, with TA having the highest activity. Temporal analysis of the MS data revealed tannin bioconversion mechanisms with a relatively higher abundance of gallic acid (m/z 169) accumulated at the end of 8 days, particularly in TA. Similarly, quercetin precursor (glycoside) metabolites were also transformed to quercetin aglycones (m/z 301) in most Acer plant extracts. The present study underscores the efficacy of fermentative bioconversion strategies aimed at enhancing the quality and availability of bioactive metabolites from plant extracts.

Review: DNA Barcoding and Chromatography Fingerprints for the Authentication of Botanicals in Herbal Medicinal Products

In the last two decades, there has been a tremendous increase in the global use of herbal medicinal products (HMPs) due to their claimed health benefits. This has led to increase in their demand and consequently, also, resulted in massive adulteration. This is due to the fact that most of the traditional methods cannot identify closely related species in a process product form. Therefore the urgent need for simple and rapid identification methods resulted in the discovery of a novel technique. DNA barcoding is a process that uses short DNA sequence from the standard genome for species identification. This technique is reliable and is not affected by external factors such as climates, age, or plant part. The difficulties in isolation of DNA of high quality in addition to other factors are among the challenges encountered using the DNA barcoding in the authentication of HMP. These limitations indicated that using DNA barcoding alone may ineffectively authenticate the HMP. Therefore, the combination of DNA barcoding with chromatographic fingerprint, a popular and generally accepted technique for the assessment and quality control of HMP, will offer an efficient solution to effectively evaluate the authenticity and quality consistency of HMP. Detailed and quality information about the main composition of the HMPs will help to ascertain their efficacy and safety as these are very important for quality control.

Metabolism of Quercetin and Naringenin by Food-Grade Fungal Inoculum, Rhizopus azygosporus Yuan et Jong (ATCC 48108)

Rhizopus azygosporus Yuan et Jong (ATCC 48108), a starter culture for fermented soybean tempeh, produces β-glucosidases that cleave flavonoid glycosides into aglycones during fermentation. However, recent data suggest that fermentation of a flavonoid glycoside-rich extract with this strain did not result in the production of aglycones. Thus, in this paper, flavonoid metabolism of this strain was investigated. Incubation of flavonoid aglycones, naringenin and quercetin, with R. azygosporus resulted in the production of flavonoid glucosyl-, hydroxyl-, and sulfo-conjugated derivatives. Naringenin was completely metabolized within 96 h into eriodictyol sulfate and eriodictyol glucoside, whereas quercetin was partially metabolized into quercetin glucoside, diglucoside, sulfate, and glucosyl-sulfate. Most of these metabolites were found to be excreted by the fungi into the culture medium. Toxicity analysis revealed that incubation with both quercetin and naringenin did not exert inhibitory effects on fungal growth. This study presents an interesting mechanism of fungal detoxification of flavonoids in foods.