Citrus peels waste as a source of value-added compounds: Extraction and quantification of bioactive polyphenols

Highly clean recovery of natural antioxidants from lemon peels: Lactic acid-based automatic solvent extraction

INTRODUCTION

Food industry generates large amounts of waste by-products rich in natural antioxidants. On the other hand, application of advanced processes for the recovery of these fine chemicals is another popular topic of recent years.

OBJECTIVE

The purpose of this study is to propose a green extraction method by application of deep eutectic solvent-based automated solvent extraction (AMSE) from lemon peels.

METHODS

The primary polyphenols (hesperidin, naringin, and p-coumaric acid) and the total polyphenols of the lemon peel extract were quantified and used as response for the optimisation of the AMSE conditions. The Box-Behnken design type of the response surface method (RSM) was chosen for optimisation study. Scavenging activity of the lemon peel extract against 2,2-diphenyl-1-picrylhydrazil (DPPH) free radical was also measured in vitro.

RESULTS

The optimum conditions for the highest total phenolic (7.47 mg-gallic acid equivalent [GAE]/g-lemon peel [LP]), naringin (5.05 mg/g-LP), p-coumaric acid (3.27 mg/g-LP), and hesperidin (0.07 mg/g-LP) yields were obtained by 1.5 h of extraction time, 46% water (v/v), and 5 g of peel. The antioxidant activity changed between 37.31% and 94.10% in the peels.

CONCLUSIONS

Extraction time was the most effective process factor for the total phenolic and p-coumaric acid yields, while water addition was statistically very important (p < 0.0001) for the naringin and hesperidin yields in the current AMSE system. The second-order models generated for the selected systems represent the data satisfyingly based on the high coefficients of determination (> 0.99), statistically significant p-values (<0.0001), coefficient of variation values (< 10%), and non-significant lack-of-fit values (p > 0.05).

Citrus Peel Flavonoid Extracts: Health-Beneficial Bioactivities and Regulation of Intestinal Microecology in vitro

Citrus peel and its extracts are rich in flavonoids, which are beneficial to human health. In this study, the extraction, component analysis, biological activity and intestinal microbiota regulation of citrus peel flavonoid extracts (CPFEs) were investigated. CPFEs from 14 Chinese cultivars were purified by ultrasound-assisted extraction and XAD-16 macroporous resin. The total flavonoid content of lemon was greatest at 103.48 ± 0.68 mg/g dry weight (DW) by NaNO2-Al(NO3)3-NaOH spectrophotometry. Using high-performance liquid chromatography–diode array detection, the highest concentrations of naringin, hesperidin and eriocitrin were found in grapefruit (52.03 ± 0.51 mg/g DW), chachiensis (43.02 ± 0.37 mg/g DW) and lemon (27.72 ± 0.47 mg/g DW), respectively. Nobiletin was the most polymethoxylflavone in chachiensis at 16.91 ± 0.14 mg/g DW. CPFEs from chachiensis and grapefruit had better antioxidant activity, α-glucosidase inhibitory and sodium glycocholate binding ability. In addition, chachiensis and grapefruit CPFEs had positive effects on intestinal microecology, as evidenced by a significant increase in the relative abundance of Bifidobacterium spp., and production of short-chain fatty acids, especially acetic acid, by a simulated human intestinal model. Collectively, our results highlight the biological function of CPFEs as prebiotic agents, indicating their potential use in food and biomedical applications.

Formulation of Biscuits Fortified with a Flour Obtained from Bergamot By-Products (Citrus bergamia, Risso)

Bergamot belongs to the Rutaceae family and is a typical fruit grown principally in the province of Reggio Calabria (South Italy). Nowadays, its industrial use is mostly related to the extraction of the essential oil contained in the flavedo but also to a lesser extent the extraction of the juice (from the pulp), which is rich in antioxidants. However, the pressed pulp (known as Pastazzo) is either used for animal feed or is discarded. The aim of this research was to study the effect of bergamot Pastazzo flour in shortbread biscuits. Pastazzo flour partially replaced the 00 wheat flour in different percentages (2.5%, 5%, 10% and 15%). Simultaneously, a sample without the addition of pastazzo flour (control) was analyzed, thus obtaining five biscuit samples. Cooking was done in a ventilated oven at 180 °C. The baking time was different for the control and the enriched samples depending on when the desired color was reached. The control took 12 min, while the enriched samples reached the desired color in 8 min. All samples were subjected to physicochemical and antioxidant characterization, as well as total polyphenols and flavonoids. The use of pastazzo flour resulted in a slight increase in water activity and humidity values. pH values decreased for all the enriched samples compared to the control, but this was more relevant for the samples enriched with 10 and 15% of flour from by-products. Hardness varied from 1823 g (Control) to 2022 and 2818 g (respectively, for 2.5% and 15% bergamot Pastazzo flour in the recipe). Total phenol content varied from 0.14 mg GAE g−1 (Control) to 0.60 and 3.64 mg GAE g−1 (respectively, for 2.5% and 15% bergamot Pastazzo flour in the recipe). The obtained results demonstrated that the use of pastazzo flour had a positive influence on the antioxidant content, with values which increased as more pastazzo flour was added.

Evaluation of Antimicrobial and Proliferation of Fibroblast Cells Activities of Citrus Essential Oils

BACKGROUND: Citrus species produce essential oils (EOs) containing various chemical components that show many pharmacological activities. AIM: The purpose of this study is to evaluate the chemical content and antimicrobial activity of EO extracted from fruit peels and leaves of Citrus x aurantifolia (“Asam sundai”) and Citrus aurantifolia (lime EOs extracted from fruit peels and leaves). METHODS: The EO was extracted by the hydrodistillation method. The chemical content was determined using gas chromatography in tandem with mass spectroscopy (GC-MS). Antibacterial activity was performed using broth microdilution method, while proliferation of fibroblast cell was carried out using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. RESULTS: The main constituent of the EO of “asam sundai” peel (MAKS) and lime peel (MAKN) was I-limonene, while the EO of “asam sundai” leaves (MADS) was γ-terpinene. MAKN EOs showed stronger antibacterial activity than MAKS and MADS with minimum inhibitory concentration values of 3.12 mg/ml against S. aureus, MRSA, and Pseudomonas aeruginosa and 6.25 mg/ml for Streptococcus mutans and Escherichia coli. Meanwhile, the highest fibroblast cell proliferation activity showed by MAKS EO at concentrations of 10, 1, and 0.1 g/ml with a percentage of the proliferation of more than 100%. CONCLUSION: It can be concluded that the different species of citrus have different chemical compositions and different biological activities.

Flowability, Rehydration Behaviour and bioactive Compounds of an Orange Powder Product as Affected by Particle Size

By offering a powder that ensures the healthy value of the fruits, a proper flowability and adequate viscosity after rehydration, there could be an opportunity to promote fruit consumption. The particle size is of critical importance with regard to the properties of a powder. But the separation of a product by particle size is usually associated with compositional changes. In this study, an orange powder product with the same composition but different particle size was compared. The particle sizes considered (269 ± 4, 189 ± 4, 118 ± 3 µm) offer a product with the same bioactive compound content and guarantee a good powder flowability: angle of repose, compressibility, density, porosity and Hausner’s and Carr’s indexes. Nevertheless, grinding can be used as a simple green technology with which to adjust the particle size so as to obtain rehydrated products with differing viscosities and, therefore, powders with different applications: the smaller the particle size, the lower the viscosity.

Fruit peel bioactives, valorisation into nanoparticles and potential applications: A review

Nanotechnology is a rapidly growing field with profound applications in different domains, particularly in food science and technology. Nanoparticles (NPs) synthesis, an integral part of nanotechnology-based applications, is broadly classified into chemical, physical and biosynthesis methods. Chemically sensitive and energy-intensive procedures employed for NPs synthesis are some of the limits of traditional chemical approaches. Recent research has focused on developing easy, nontoxic, cost-effective, and environment-friendly NPs synthesis during the last decade. Biosynthesis approaches have been developed to achieve this goal as it is a viable alternative to existing chemical techniques for the synthesis of metallic nanomaterials. Fruit peels contain abundant bioactive compounds including phenols, flavonoids, tannins, triterpenoids, steroids, glycosides, carotenoids, anthocyanins, ellagitannins, vitamin C, and essential oils with substantial health benefits, anti-bacterial and antioxidant properties, generally discarded as byproduct or waste by the fruit processing industry. NPs synthesized using bioactive compounds from fruit peel has futuristic applications for an unrealized market potential for nutraceutical and pharmaceutical delivery. Numerous studies have been conducted for the biosynthesis of metallic NPs such as silver (AgNPs), gold (AuNPs), zinc oxide, iron, copper, palladium and titanium using fruit peel extract, and their synthesis mechanism have been reported in the present review. Additionally, NPs synthesis methods and applications of fruit peel NPs have been discussed.

Chemical Variation of Chenpi (Citrus Peels) and Corresponding Correlated Bioactive Compounds by LC-MS Metabolomics and Multibioassay Analysis

The peel of Citrus reticulata “Chachi” (CP) possesses various health-promoting benefits and is not only one of the most famous Chinese herbal medicine, but also an ingredient in fermented foods. In the present study, the effects of storage years (1-, 3-, 4-, 5-, 6-, and 11-years) on the chemical profiling and potential bioactive compounds of CP were compared by metabolomics and in vitro bioactivity analysis. With the increase of storage time, the content of hesperidin significantly decreased, but nobiletin, 3,5,6,7,8,3′,4′-heptamethoxyflavone, and tangeretin were increased. Meanwhile, the antioxidant activity of CP was enhanced. Phenolic acids, flavonol glycosides, fatty acids, and alkyl glycosides were marker compounds that were responsible for distinguishing the storage time of CP. Correlation analysis suggested that some polyphenols including quercetin-glucoside, quinic acid, trihydroxydimethoxyflavone, and rutin were potential antioxidant compounds in CP. The dichloromethane and n-butanol fractions showed the better antioxidant capacity and inhibitory effects on glucose-hydrolysis enzymes. They mainly contained ferulic acid, nobiletin, 3,5,6,7,8,3′,4′-heptamethoxyflavone, kaempferol, and hesperidin.

Flowability, Rehydration Behaviour and bioactive Compounds of an Orange Powder Product as Affected by Particle Size

By offering a powder that ensures the healthy value of the fruits, a proper flowability and adequate viscosity after rehydration, there could be an opportunity to promote fruit consumption. The particle size is of critical importance with regard to the properties of a powder. But the separation of a product by particle size is usually associated with compositional changes. In this study, an orange powder product with the same composition but different particle size was compared. The particle sizes considered (269 ± 4, 189 ± 4, 118 ± 3 µm) offer a product with the same bioactive compound content and guarantee a good powder flowability: angle of repose, compressibility, density, porosity and Hausner’s and Carr’s indexes. Nevertheless, grinding can be used as a simple green technology with which to adjust the particle size so as to obtain rehydrated products with differing viscosities and, therefore, powders with different applications: the smaller the particle size, the lower the viscosity.

Determination of Bioactive Components in Mandarin Fruits: A Review

During the last decade, there has been a continuous rise in the consumption of fresh easy-to-peel mandarins. However, the majority of the knowledge comes from other citrus fruit, like orange, while there are relatively few studies about mandarins and no comprehensive research on literature data about them. One of the most important steps in the analytical process is sample preparation. Its value is evident in analyzing the samples with complex matrices, such as in mandarin fruit. In addition, mandarin contains hundreds to thousands of various compounds and metabolites, some of them present in extremely low concentrations, that interfere with the detection of one another. Hence, mandarin samples are commonly pretreated by extraction to facilitate analysis of bioactive compounds, improve accuracy and quantification levels. There is an abundance of extraction techniques available, depending on the group of compounds of interest. Finally, modern analytical techniques, have been applied to cope with numerous bioactive compounds in mandarins. Considering all the above, this review aims to (i) list the most valuable procedures of sample preparation, (ii) highlight the most important techniques for extraction of bioactive compounds from mandarin fruit, and (iii) summarize current trends in the identification and determination of bioactive compounds in mandarin.

A combined analytical-chemometric approach for the in vitro determination of polyphenol bioaccessibility by simulated gastrointestinal digestion

In this study, an integrated characterisation through polyphenol and caffeine content and antioxidant activity was combined with chemometric analysis to assess the effects of simulated in vitro gastrointestinal digestion on the bioaccessibility of these bioactive compounds from nine different tea infusions. Tea infusions were characterised based on total flavonoids, total polyphenols and antioxidant activity, together with the determination of individual polyphenol content. Fourteen phenolic compounds, including phenolic acids, stilbenes and flavonoids, were selected based on their reported bioactivity and high accessibility, attributed to their low molecular weight. Both polyphenols and caffeine were initially monitored in raw tea infusions and through the different digestion stages (salivary, gastric and duodenal) by capillary high performance liquid chromatography coupled to diode array detection (cHPLC-DAD) and/or HPLC coupled to a triple quadrupole mass analyser (HPLC–MS/MS). Multivariate analysis of the studied bioactives, using principal component analysis and cluster analysis, revealed that the decaffeination process seems to increase the stability and concentration of the compounds evaluated during digestion. The greatest transformations occurred mainly in the gastric and duodenal stages, where low bioactivity indices (IVBA) were shown for resveratrol and caffeic acid (IVBA = 0%). In contrast, the polyphenols gallic acid, chlorogenic acid and quercetin gave rise to their availability in white, green and oolong infusion teas (IVBA > 90%). Furthermore, highly fermented black and pu-erh varieties could be designated as less bioaccessible environments in the duodenum with respect to the tested compounds.

A Green Extraction Method to Achieve the Highest Yield of Limonin and Hesperidin from Lime Peel Powder (Citrus aurantifolia)

Green extraction is aimed at reducing energy consumption by using renewable plant sources and environmentally friendly bio-solvents. Lime (Citrus aurantifolia) is a rich source of flavonoids (e.g., hesperidin) and limonoids (e.g., limonin). Manufacturing of lime products (e.g., lime juice) yields a considerable amount of lime peel as food waste that should be comprehensively exploited. The aim of this study was to develop a green and simple extraction method to acquire the highest yield of both limonin and hesperidin from the lime peel. The study method included ethanolic-aqueous extraction and variable factors, i.e., ethanol concentrations, pH values of solvent, and extraction temperature. The response surface methodology was used to optimize extraction conditions. The concentrations of limonin and hesperidin were determined by using UHPLC-MS/MS. Results showed that the yields of limonin and hesperidin significantly depended on ethanol concentrations and extraction temperature, while pH value had the least effect. The optimal extraction condition with the highest amounts of limonin and hesperidin was 80% ethanol at pH 7, 50 °C, which yields 2.072 and 3.353 mg/g of limonin and hesperidin, respectively. This study illustrates a green extraction process using food waste, e.g., lime peel, as an energy-saving source and ethanol as a bio-solvent to achieve the highest amount of double bioactive compounds.

Optimization of the extraction conditions of Nypa fruticans Wurmb. using response surface methodology and artificial neural network

In this study, we conducted response surface methodology (RSM) and artificial neural network (ANN) to predict and estimate the optimized extraction condition of Nypa fruticans Wurmb. (NF). The effect of ethanol concentration (X₁; 0-100%), extraction time (X₂; 6-24 h), and extraction temperature (X₃; 40-60 °C) on the antioxidant potential was confirmed. The optimal conditions (57.6% ethanol, 19.0 h extraction time, and 51.3 °C extraction temperature) of 2,2-diphenyl-1-1picrylhydrazyl (DPPH) scavenging activity, cupric reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP), total phenolic content (TPC), and total flavonoid contents (TFC) resulted in a maximum value of 62.5%, 41.95 and 48.39 µM, 143.6 mg GAE/g, and 166.8 CAE/g, respectively. High-resolution mass spectroscopic technique was performed to profile phenolic and flavonoid compounds. Upon analyzing, total 48 compounds were identified in NF. Altogether, our findings can provide a practical approach for utilizing NF in various bioindustries.

Valorization of Taiwan's Citrus depressa Hayata peels as a source of nobiletin and tangeretin using simple ultrasonic-assisted extraction

As the highest yield crop worldwide, citrus peels that possess bioactive compounds were discarded as a futile by-product. Ultrasonication with environmentally friendly solvent (50% ethanol and ddH₂O) were used in the present study to extract flavonoids from Citrus depressa Hayata peels with extraction period and fruit maturity as other variables. DPPH scavenging activity was investigated. Qualitative flavonoid content analysis was done by UV/Vis and FTIR-ATR spectra. Quantification of flavonoid using LC-MS/MS found that solvent type, fruit maturity, and ultrasonication period significantly affect the extracted flavonoid yield (p < 0.05). Extraction using 50% ethanol showed a higher yield than ddH₂O. Flavonoid content was also higher in unripe than ripe samples. Nobiletin, tangeretin, and rutin were dominant among the identified compounds in all sample treatments. Flavonoid content in Citrus depressa Hayata extract was found to negatively correlate to DPPH scavenging activity, which needs further research to identify other bioactivities of these flavonoids.

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Utilization of simple ultrasonication method with less preparation to extract flavonoids from Citrus depressa Hayata peels.

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Fruit maturity, extraction time and solvent preference significantly affect the yield of extracted flavonoid.

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Environmentally friendly solvent for extraction, deliver a comparable yield of flavonoid compounds to other methods.

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The negative correlation of extracted flavonoid to DPPH scavenging activity.

Influence of the extraction method on the recovery of bioactive phenolic compounds from food industry by-products

Agro-foodindustries generate colossal amounts of non-edible waste and by-products, easily accessible as raw materials for up-cycling active phytochemicals. Phenolic compounds are particularly relevant in this field given their abundance in plant residues and the market interest of their functionalities (e.g. natural antioxidant activity) as part of nutraceutical, cosmetological and biomedical formulations. In "bench-to-bedside" achievements, sample extraction is essential because valorization benefits from matrix desorption and solubilization of targeted phytocompounds. Specifically, the composition and polarity of the extractant, the optimal sample particle size and sample:solvent ratio, as well as pH, pressure and temperature are strategic for the release and stability of mobilized species. On the other hand, current green chemistry environmental rules require extraction approaches that eliminate polluting consumables and reduce energy needs. Thus, the following pages provide an update on advanced technologies for the sustainable and efficient recovery of phenolics from plant matrices.

Recovery of Added-Value Compounds from Orange and Spinach Processing Residues: Green Extraction of Phenolic Compounds and Evaluation of Antioxidant Activity

Phenolic compounds recovery by mechanical stirring extraction (MSE) was studied from orange and spinach wastes using water as a solvent. The statistical analysis showed that the highest total polyphenol content (TPC) yield was obtained using 15 min, 70 °C, 1:100 (w/v) solid/solvent ratio and pH 4 for orange; and 5 min, 50 °C, 1:50 (w/v) solid/solvent ratio and pH 6 for spinach. Under these conditions, the TPC was 1 mg gallic acid equivalent (GAE) g^-1 fresh weight (fw) and 0.8 mg GAE g^-1 fw for orange and spinach, respectively. MSE substantially increased the phenolic compounds yields (1-fold for orange and 2-fold for spinach) compared with ultrasound-assisted extraction. Furthermore, the antioxidant activity of orange and spinach extracts was evaluated using DPPH, FRAP and ABTS. The obtained results pointed out that the evaluated orange and spinach residues provided extracts with antioxidant activity (2.27 mg TE g^-1 and 0.04 mg TE g^-1, respectively).

Isolation, optimized extraction, and ultra-high performance liquid chromatography with photodiode array method for quantitative analysis of chiratol in Swertia paniculata

The global natural product-based industry is growing fast with the introduction of new phytochemicals and herbal extract products from different geographical regions. Swertia paniculata is a well-known plant with medicinal properties; however, the quality control for its major phytochemical constituents from the Himalayan geographical region is nevertheless reported. Therefore, the first objective of this investigation was to characterize and optimize the extraction process while the second objective was to validate a quantitative analytical method for chiratol from S. paniculata herbal extract. The chiratol was characterized with spectral analysis. The optimum extraction condition for the highest yield of metabolite was realized in chloroform as a solvent system under ultrasonication. The ultra-high performance liquid chromatography coupled with photodiode array detection method for analytical quantification was validated for specificity, linearity, limits of detection, limits of quantification, precision, repeatability, recovery, and robustness using Eclipse Plus C18 column (100 mm × 4.6 mm × 3.5 μm id). The gradient elution of water/acetonitrile as mobile phase was used at a flow rate of 0.5 ml/min. The recovery percentage was very satisfactory with values within specification. The robustness parameters showed no substantial influence of evaluated parameters by the Youden test. The developed method was ascertained to be appropriate for the proposed purpose.

Citrus Genus and Its Waste Utilization: A Review on Health-Promoting Activities and Industrial Application

Citrus fruits such as oranges, grapefruits, lemons, limes, tangerines, and mandarins, whose production is increasing every year with the rise of consumer demand, are among the most popular fruits cultivated throughout the globe. Citrus genus belongs to the Rutaceae family and is known for its beneficial effects on health for centuries. These plant groups contain many beneficial nutrients and bioactive compounds. These compounds have antimicrobial, anticancer, antidiabetic, antiplatelet aggregation, and anti-inflammatory activities. Citrus waste, generated by citrus-processing industries in large amounts every year, has an important economic value due to richness of bioactive compounds. The present review paper has summarized the application and properties of Citrus and its waste in some fields such as food and drinks, traditional medicine practices, and recent advances in modern approaches towards pharmaceutical and nutraceutical formulations.

Green Extraction of Bioactive Compounds from Plant Biomass and Their Application in Meat as Natural Antioxidant

Plant extracts are rich in various bioactive compounds exerting antioxidants effects, such as phenolics, catechins, flavonoids, quercetin, anthocyanin, tocopherol, rutin, chlorogenic acid, lycopene, caffeic acid, ferulic acid, p-coumaric acid, vitamin C, protocatechuic acid, vitamin E, carotenoids, β-carotene, myricetin, kaempferol, carnosine, zeaxanthin, sesamol, rosmarinic acid, carnosic acid, and carnosol. The extraction processing protocols such as solvent, time, temperature, and plant powder should be optimized to obtain the optimum yield with the maximum concentration of active ingredients. The application of novel green extraction technologies has improved extraction yields with a high concentration of active compounds, heat-labile compounds at a lower environmental cost, in a short duration, and with efficient utilization of the solvent. The application of various combinations of extraction technologies has proved to exert a synergistic effect or to act as an adjunct. There is a need for proper identification, segregation, and purification of the active ingredients in plant extracts for their efficient utilization in the meat industry, as natural antioxidants. The present review has critically analyzed the conventional and green extraction technologies in extracting bioactive compounds from plant biomass and their utilization in meat as natural antioxidants.

Application of Emerging Cell Disintegration Techniques for the Accelerated Recovery of Curcuminoids from Curcuma longa

Curcuminoids, the bioactive compounds with many beneficial effects on human health, exist in Curcuma longa (turmeric). In the present study, the impact of different cell disintegration techniques to enhance total curcuminoid recovery (TC) from fresh and dried turmeric was investigated. The impact of thermal pretreatment (TP), ultrasound pretreatment (UP), enzyme pretreatment (EP), and pulsed electric field pretreatment (PEF) on the recovery of curcumin (CUR), demethoxycurcumin (DMC), and bis-demethoxycurcumin (BDMC) from fresh and dried turmeric were studied. The cell disintegration index (Zp) and high-performance liquid chromatography (HPLC) analysis of curcuminoids were performed to evaluate the efficiency of the applied techniques. With fresh turmeric, the highest curcuminoid recovery was 83.6 mg/g dry basis with EP. The highest structural tissue damage was obtained with UP achieving a cell disintegration level of 92.5%. The technology with the highest time-saving and low specific energy input was PEF with a total curcuminoid recovery of 80.9 mg/g dry basis. Working with dried turmeric, the drying required high specific energy input for 72 h at 50 °C; however, the untreated dried sample reached 125.3 mg/g dry basis of TC without further pretreatment after drying.

Enzymatic processing of Citrus reticulata (Kinnow) pomace using naringinase and its valorization through preparation of nutritionally enriched pasta

Citrus fruits are consumed either as whole fruits or as juice after processing. Processing of fruits yields a significant number of by-products in the form of pulp, peel and seeds, which are often discarded and major cause of environmental concern. Bitterness in the waste residue of citrus products is one of the leading hindrance in its valorization and supplementation in other food products. Aim of this study was to reduce the bitterness of Citrus reticulata (kinnow) pomace using enzymatic method and its supplementation in production of nutritionally rich pasta. Under optimized conditions (1U/mg enzyme naringinase concentration, temperature 50 °C, at pH 4.5 and treatment time 4 h), the maximum reduction (65.95%) of naringin (bitterness causing compound) was observed coupled with increase (60.13%) in naringenin (non-bitter compound). The debittered kinnow pomace has been further characterized for physio-chemical changes and morphological changes before and after treatment. The debittered kinnow pomace was then supplemented for the preparation of antioxidant and nutrient enriched pasta.

Characterization of Citrusnobilis Peel Methanolic Extract for Antioxidant, Antimicrobial, and Anti-Inflammatory Activity

Currently, the potential utilization of fruits and vegetable waste as a source of micronutrients and antioxidants has increased. The present study, therefore, aimed to determine the antimicrobial and anti-inflammatory activities of Citrus nobilis peel extract. A modified solvent evaporation technique was employed for peel extract preparation. For effective utilization of the natural product, quantitative analysis of phenolic compounds was carried out using liquid chromatography and mass spectroscopy technique. Phenolic and flavonoids were present in high amounts, while β-carotene and lycopene were present in vestigial amounts. The antimicrobial efficiency of peel extract was evaluated against four bacterial strains including Staphylococcus aureus (MTCC 3160), Klebsiella pneumoniae (MTCC 3384), Pseudomonas aeruginosa (MTCC 2295), and Salmonella typhimurium (MTCC 1254), and one fungal strain Candida albicans (MTCC 183), and zone of inhibition was comparable to the positive control streptomycin and amphotericin B, respectively. The extract of Citrus nobilis peels showed effective anti-inflammatory activity during human red blood cell membrane stabilization (HRBC) and albumin denaturation assay. The extracts also exhibited 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity ranging from 53.46 to 81.13%. Therefore, the obtained results suggest that Citrus nobilis peel could be used as an excellent source of polyphenols and transformed into value-added products.

Potential In Vitro Inhibition of Selected Plant Extracts against SARS-CoV-2 Chymotripsin-Like Protease (3CLPro) Activity

Antiviral treatments inhibiting Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication may represent a strategy complementary to vaccination to fight the ongoing Coronavirus disease 19 (COVID-19) pandemic. Molecules or extracts inhibiting the SARS-CoV-2 chymotripsin-like protease (3CLPro) could contribute to reducing or suppressing SARS-CoV-2 replication. Using a targeted approach, we identified 17 plant products that are included in current and traditional cuisines as promising inhibitors of SARS-CoV-2 3CLPro activity. Methanolic extracts were evaluated in vitro for inhibition of SARS-CoV-2 3CLPro activity using a quenched fluorescence resonance energy transfer (FRET) assay. Extracts from turmeric (Curcuma longa) rhizomes, mustard (Brassica nigra) seeds, and wall rocket (Diplotaxis erucoides subsp. erucoides) at 500 µg mL-1 displayed significant inhibition of the 3CLPro activity, resulting in residual protease activities of 0.0%, 9.4%, and 14.9%, respectively. Using different extract concentrations, an IC50 value of 15.74 µg mL-1 was calculated for turmeric extract. Commercial curcumin inhibited the 3CLPro activity, but did not fully account for the inhibitory effect of turmeric rhizomes extracts, suggesting that other components of the turmeric extract must also play a main role in inhibiting the 3CLPro activity. Sinigrin, a major glucosinolate present in mustard seeds and wall rocket, did not have relevant 3CLPro inhibitory activity; however, its hydrolysis product allyl isothiocyanate had an IC50 value of 41.43 µg mL-1. The current study identifies plant extracts and molecules that can be of interest in the search for treatments against COVID-19, acting as a basis for future chemical, in vivo, and clinical trials.

Dynamics of Phloridzin and Related Compounds in Four Cultivars of Apple Trees during the Vegetation Period

Apple trees (Malus domestica Borgh) are a rich source of dihydrochalcones, phenolic acids and flavonoids. Considering the increasing demand for these phytochemicals with health-benefitting properties, the objective of this study was to evaluate the profile of the main bioactive compounds—phloridzin, phloretin, chlorogenic acid and rutin—in apple tree bark, leaves, flower buds and twigs. The variety in the phenolic profiles of four apple tree cultivars was monitored during the vegetation period from March to September using chromatography analysis. Phloridzin, the major glycoside of interest, reached the highest values in the bark of all the tested cultivars in May (up to 91.7 ± 4.4 mg g⁻¹ of the dried weight (DW), cv. ‘Opal’). In the leaves, the highest levels of phloridzin were found in cv. ‘Opal’ in May (82.5 ± 22.0 mg g⁻¹ of DW); in twigs, the highest levels were found in cv. ‘Rozela’ in September (52.4 ± 12.1 mg g⁻¹ of DW). In the flower buds, the content of phloridzin was similar to that in the twigs. Aglycone phloretin was found only in the leaves in relatively low concentrations (max. value 2.8 ± 1.4 mg g⁻¹ of DW). The highest values of rutin were found in the leaves of all the tested cultivars (10.5 ± 2.9 mg g⁻¹ of DW, cv. ‘Opal’ in September); the concentrations in the bark and twigs were much lower. The highest content of chlorogenic acid was found in flower buds (3.3 ± 1.0 mg g⁻¹ of DW, cv. ‘Rozela’). Whole apple fruits harvested in September were rich in chlorogenic acid and phloridzin. The statistical evaluation by Scheffe’s test confirmed the significant difference of cv. ‘Rozela’ from the other tested cultivars. In conclusion, apple tree bark, twigs, and leaves were found to be important renewable resources of bioactive phenolics, especially phloridzin and rutin. The simple availability of waste plant material can therefore be used as a rich source of phenolic compounds for cosmetics, nutraceuticals, and food supplement preparation.

Valorization of Citrus Co-Products: Recovery of Bioactive Compounds and Application in Meat and Meat Products

Citrus fruits (orange, lemon, mandarin, and grapefruit) are one of the most extensively cultivated crops. Actually, fresh consumption far exceeds the demand and, subsequently, a great volume of the production is destined for the citrus-processing industries, which produce a huge quantity of co-products. These co-products, without proper treatment and disposal, might cause severe environmental problems. The co-products obtained from the citrus industry may be considered a very important source of high-added-value bioactive compounds that could be used in the pharmaceutical, cosmetic, and dietetic industries, and mainly in the food industry. Due to consumer demands, the food industry is exploring a new and economical source of bioactive compounds to develop novel foods with healthy properties. Thus, the aim of this review is to describe the possible benefits of citrus co-products as a source of bioactive compounds and their applications in the development of healthier meat and meat products.

Antioxidant and antimicrobial activities and UPLC-ESI-MS/MS polyphenolic profile of sweet orange peel extracts

With growing consumer awareness, exploitation of renewable resources is cost-effective and environment friendly. This work examines the potential of citrus peels as natural antioxidants and antimicrobials for food preservation. Extraction yield, total soluble phenols and flavonoids of various citrus peels (sweet orange, lemon, tangerine and grapefruit) were optimized by varying the solvent type. While the highest extract yield (~16 ​g/100g) was obtained from the sweet orange peels in methanol, extraction with ethanol maximized the concentration of total phenols and flavonoids (~80 ​mg catechol equivalents/100 ​g dry weight). In addition, sweet orange peel extract showed the highest DPPH, ABTS and hydroxyl radical scavenging values. UPLC-ESI-MS/MS analysis of aqueous and ethanolic extracts of sweet orange peels revealed more than 40 polyphenolic compounds including phenolic acids and flavonoids, some of which have not been previously reported. The predominant polyphenols were narirutin, naringin, hesperetin-7-O-rutinoside naringenin, quinic acid, hesperetin, datiscetin-3-O-rutinoside and sakuranetin. The incorporation of sweet orange peel extract into two vegetable oils enhanced their oxidative stability. In addition, all citrus peel extracts possessed high antimicrobial activity against several food-borne pathogens, and the activity was highest for the sweet orange peel extract. Overall results suggested the great potential of sweet orange peels as natural antioxidant and antimicrobials, which can be efficiently extracted using a simple and low-cost method, for enhancing the storage stability and safety of vegetable oils.

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Citrus peels extracts exhibited high contents of polyphenols and flavonoids with high antioxidant and antimicrobial capacities.

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Sweet orange peel extracts in ethanol and water showed high yield of polyphenols and flavonoids.

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The polyphenolic compounds (~40) in sweet orange peel extracts were identified and quantified by UPLC-ESI-MS/MS.

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Supplementing orange peel extract into edible oils prevented rancidity.

Phenolic Compounds Profile and Antioxidant Capacity of Pitahaya Fruit Peel from Two Red-Skinned Species (Hylocereus polyrhizus and Hylocereus undatus)

Pitahaya peel is a good source of bioactive polyphenols. However, the bound phenolics and their antioxidant activity remain unclear. The bound phenolics of pitahaya peel from two red-skinned species with red pulp (RP) and white pulp (WP) were released with different methods (acid, base, and composite enzymes hydrolysis). The results revealed that base hydrolysis was the most efficient method for releasing the bound phenolics from RP (11.6 mg GAE/g DW) and WP (10.5 mg GAE/g DW), which was 13.04-fold and 8.18-fold for RP and 75.07-fold and 10.94-fold for WP compared with acid hydrolysis and enzymatic hydrolysis, respectively. A total of 37 phenolic compounds were identified by UPLC-TOF/MS with most chlorogenic acid, caffeic acid, ferulic acid and p-coumaric acid in RP, whereas chlorogenic acid, caffeic acid, ferulic acid, rutin and isoquercitrin were the main compounds in WP. Regardless of the hydrolysis method, the extracts having the highest phenolic content showed the strongest antioxidant activities. The work shows that hydrolysis methods have a significant effect on the release of phenolics, and the contents of major characteristic bound phenolic compounds are related to the ecological type of pitahaya.

Antioxidant Activity and Healthy Benefits of Natural Pigments in Fruits: A Review

Natural pigments, including carotenoids, flavonoids and anthocyanidins, determine the attractive color of fruits. These natural pigments are essential secondary metabolites, which play multiple roles in the whole life cycle of plants and are characterized by powerful antioxidant activity. After decades of research and development, multiple benefits of these natural pigments to human health have been explored and recognized and have shown bright application prospects in food, medicine, cosmetics and other industries. In this paper, the research progress of natural fruit pigments in recent years was reviewed, including the structural characteristics and classification, distribution in fruits and analysis methods, biosynthetic process, antioxidant capacity and mechanism, bioaccessibility and bioavailability, and health benefits. Overall, this paper summarizes the recent advances in antioxidant activity and other biological functions of natural fruit pigments, which aims to provide guidance for future research.

Application of accelerating energies to the maceration of sherry vinegar with citrus fruits

BACKGROUND

In the present work we propose the use of accelerating energies (microwaves and ultrasounds) to the maceration process of sherry vinegar with citrus fruit peels (orange and lemon). For the application of microwaves, an experimental design has been developed in order to optimize the maceration conditions. To evaluate the effect of these energies on the maceration, the volatile and polyphenolic content of the samples has been analyzed, as well as their sensory characteristics.

RESULTS

Orange peel provided a higher number of volatile and polyphenolic compounds to the vinegar, while lemon's yielded a greater amount of some of them. The multivariate analysis showed that the samples macerated using microwaves were the most similar to the samples macerated in the traditional way. This aspect was corroborated by the sensory analysis, which was more noticeable when orange peel was used in the macerations.

CONCLUSION

Therefore, it seems that the use of microwaves to accelerate maceration is a good alternative to the traditional method of making sherry vinegars macerated with citrus peel, since it cuts down the maceration time from 3 days to just a few minutes. © 2020 Society of Chemical Industry.

A combined approach based on matrix solid-phase dispersion extraction assisted by titanium dioxide nanoparticles and liquid chromatography to determine polyphenols from grape residues

A simple and efficient low-cost matrix solid phase dispersion (MSPD) extraction assisted by TiO₂ nanoparticles and diatomaceous earth has been developed for the extraction of phenolic compounds from grape and grape pomace wastes. Experimental conditions for MSPD extraction were optimized by a factorial design and a surface response methodology. The simultaneous identification and quantification of eight main natural polyphenols (caffeic, p-coumaric, dihydroxybenzoic and gallic acid, rutin, resveratrol, quercetin and catechin) was possible by combining MSPD and capillary liquid chromatography coupled to a diode array detection and a mass simple quadrupole analyzer (cLC-DAD-MS). Good linearity and acceptable LOD (0.05-62 µg·g^-1) and LOQ (0.2-207 µg·g^-1) were obtained. The quantities of extracted polyphenols were within 2.4 and 333 µg·g^-1, with catechin and rutin the most abundant compounds in grape pomace and grape wastes, respectively. Furthermore, considering the prospective uses of the winery bioresidues, the extracts have been characterised in terms of bioactive properties (several antioxidant activities and bacterial inhibition against Staphylococcus aureus, Escherichia coli and Pseudomona aeruginosa) and parameters such as total polyphenol and total flavonoid content. The high antioxidant activity (IC₅₀ 5.0 ± 0.4 µg ·g^-1 against DPPH radical) and antibacterial activity (2.2 ± 0.3 mg·mL^-1) suggests that the methodology developed is efficient, rapid and promising for the extraction of phenolic compounds with potential application as bioactive ingredients in food and cosmetic industries.

Techniques and modeling of polyphenol extraction from food: a review

There is a growing demand for vegetal food having health benefits such as improving the immune system. This is due in particular to the presence of polyphenols present in small amounts in many fruits, vegetables and functional foods. Extracting polyphenols is challenging because extraction techniques should not alter food quality. Here, we review technologies for extracting polyphenolic compounds from foods. Conventional techniques include percolation, decoction, heat reflux extraction, Soxhlet extraction and maceration, whereas advanced techniques are ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, high-voltage electric discharge, pulse electric field extraction and enzyme-assisted extraction. Advanced techniques are 32-36% more efficient with approximately 15 times less energy consumption and producing higher-quality extracts. Membrane separation and encapsulation appear promising to improve the sustainability of separating polyphenolic compounds. We present kinetic models and their influence on process parameters such as solvent type, solid and solvent ratio, temperature and particle size.

Electrosynthesis of three-dimensional nanoporous nickel on screen-printed electrode used for the determination of narirutin in citrus wastewater

In this study, an electrochemical sensor was designed for the detection of narirutin using three-dimensional nanostructured porous nickel on screen-printed electrode (3DnpNi/SPE). The modified electrode was successfully synthesized by the dynamic hydrogen bubble template method. The 3DnpNi/SPE was characterized by spectroscopic, microscopic, and electrochemical methods. The results showed that the 3DnpNi/SPE presents good electrocatalytic activity for the oxidation of narirutin. The quantification of narirutin was conducted by differential pulse voltammetry, which showed a wide concentration range (1.0 × 10^-7 - 1.0 × 10^-5 mol L^-1), with low detection limit (3.9 × 10^-8 mol L^-1), and excellent sensitivity (0.31 A L mol^-1). The proposed electrode was applied toward the determination of narirutin in yellow water sample from the citrus industry, where it presented a good degree of accuracy. The 3DnpNi/SPE showed repeatability, long-term stability, and selectivity. The results obtained showed agreement with those obtained by HPLC/DAD method. Chemical compounds studied in this article.

Citrus decoction by-product represents a rich source of carotenoid, phytosterol, extractable and non-extractable polyphenols

This study aimed to carry out an exhaustive chemical characterization of citrus (orange, mandarin, and grapefruit) decoctions as well as the residues obtained during the decoction process (by-products). The citrus decoctions were rich in hesperidin, naringin, and narirutin, but carotenoids and phytosterols were not detected. Interestingly, these flavanones were found in a higher concentration in the extractable polyphenol fraction of the citrus decoction by-products. Moreover, the greatest content of hesperidin and naringin was found bound to the food matrix by ether/ester bonds. Violaxanthin and β-cryptoxanthin were found as major carotenoids in the orange and mandarin decoction by-products, respectively, whereas the grapefruit decoction by-product showed a low content of carotenoids. All citrus by-products showed β-sitosterol as the major phytosterol, followed by β-campesterol. Therefore, the by-products obtained during the elaboration of citrus decoctions are rich sources of bioactive compounds that can be used for the development of functional foods or dietary supplements.

Anti-inflammatory activity of ethyl acetate and n-butanol extracts from Ranunculus macrophyllus Desf. and their phenolic profile

ETHNOPHARMACOLOGICAL RELEVANCE

The members of the genus Ranunculus have counter-irritating properties and thus, they are traditionally used for treating anti-inflammatory disorders and other skin conditions. Ranunculus macrophyllus Desf. is a wild medicinal plant growing in Algeria and traditionally used to treat some cutaneous skin disorders.

AIM

The aim of this study was to characterize the composition of the ethyl acetate and n-butanol extracts from Ranunculus macrophyllus Desf. as well as to elucidate and to compare their effect against acute skin inflammation. Moreover, both the antioxidant activity and the acute toxicity of the plant extracts were also studied.

MATERIALS AND METHODS

Spectrophotometric and chromatographic methods were employed to identify and quantify phenolic compounds and triterpenoids from R. macrophyllus Desf. fractions. The antioxidant activity was estimated using the phosphomolebdenum, DPPH, reducing power and β-carotene bleaching assays. The ethyl acetate and n-butanol extracts were screened for their anti-inflammatory activities using ex-vivo membrane stabilizing assays and in-vivo acute skin inflammation model.

RESULTS

Ethyl acetate fraction showed the highest amounts of total phenolic compounds (413 ± 4 μg GAE/mg extract) and triterpenoids (70.4 ± 1.8 μg UAE/mg extract). Rutin, hesperidin, myricetin and kaempferol were the major compounds identified in the different fractions. Ethyl acetate fraction exhibited strong DPPH^• radical scavenging ability (IC₅₀ 1.6 ± 0.2 μg/mL), high total antioxidant capacity (447 ± 7 μg AAE/mg extract) and reducing power (514 ± 8 μg AAE/mg extract). Ethyl acetate fraction inhibited (73.4 ± 0.3) % of linoleic acid peroxidation. Ethyl acetate and n-butanol fractions did not have any visible toxicity at 2000 mg/kg and presented excellent membrane stabilizing ability. The inhibition of xylene induced ear inflammation was (38 ± 4) % and (46 ± 1) % for RM-B and RM-EA, respectively.

CONCLUSIONS

The high content of both phenolic compounds and triterpenoids combined with the remarkable anti-inflammatory effect and antioxidant activity of ethyl acetate and n-butanol extracts from R. macrophyllus Desf. support the wide spread use of this traditional plant on some skin disorders (inflammatory skin disorders).

Industrial Fruits By-Products and Their Antioxidant Profile: Can They Be Exploited for Industrial Food Applications?

Fruit by-products have a low economic value and have proven biological activities, such as antioxidant capacity due to the presence of active compounds. The main objective of this study was to obtain and determine the antioxidant capacity, through DPPH radical assay and β-carotene bleaching assay, of three food grade extracts from apple, lemon, and orange industrial by-products. Furthermore, the extracts were characterized by ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS/MS). LC with diode array detector (LC-DAD) was used for the quantification of the main polyphenols. Lemon extract presented the highest inhibition percentage of DPPH radical (51.7%) and the highest total phenolics content (43.4 mg GAE/g) from the by-products studied. Orange by-product was that with the higher number of polyphenols while lemon extract was that with the highest content of individual phenolics. The by-product obtained from the lemon was that with higher amounts of hydroxycinnamic acids (407 µg/g of by-product), mainly chlorogenic acid (386.7 µg/g), followed by the apple by-product (128.0 µg/g of by-product), which showed higher amounts of rosmarinic and chlorogenic acids. These industrial by-products have great potential as a source of natural antioxidants to be used directly as food additives or to be incorporated in packaging to produce active food packaging.

Selective extraction of bioactive compounds from plants using recent extraction techniques: A review

Plant extraction has existed for a long time and is still of interest. Due to technological improvements, it is now possible to obtain extracts with higher yields. While global yield is a major parameter because it assesses the extraction performance, it can be of interest to focus on the extraction of particular compounds (specific metabolites) to enrich the sample and to avoid the extraction of unwanted ones, for instance the primary metabolites (carbohydrates, triacylglycerols). The objective then is to improve extraction selectivity is then considered. In solid-liquid extraction, which is often called maceration, the solvent has a major impact on selectivity. Its polarity has a direct influence on the solutes extracted, related to the chemical structure of the compounds, and modelling compound/solvent interactions by using various polarity or interaction scales is a great challenge to favor the choice of the appropriate extracting liquid. Technical advances have allowed the development of recent, and sometimes green, extraction techniques, such as Microwave-Assisted Extraction (MAE), Ultrasound-Assisted Extraction (UAE), Pressurized Liquid Extraction (PLE) and Supercritical Fluid Extraction (SFE). This review focuses on the specificity of these recent techniques and the influence of their physical parameters (i.e. pressure, intensity, etc.). In addition to the solvent selection, which is of prime interest, the physical parameters applied by the different techniques influence the extraction results in different ways. Besides, SFE is a versatile and green technique suitable to achieve selectivity for some compounds. Due to its properties, SC-CO₂ allows tailoring conditions to improve the selectivity.

Antioxidant Molecules from Plant Waste: Extraction Techniques and Biological Properties

The fruit, vegetable, legume, and cereal industries generate many wastes, representing an environmental pollution problem. However, these wastes are a rich source of antioxidant molecules such as terpenes, phenolic compounds, phytosterols, and bioactive peptides with potential applications mainly in the food and pharmaceutical industries, and they exhibit multiple biological properties including antidiabetic, anti-obesity, antihypertensive, anticancer, and antibacterial properties. The aforementioned has increased studies on the recovery of antioxidant compounds using green technologies to value plant waste, since they represent more efficient and sustainable processes. In this review, the main antioxidant molecules from plants are briefly described and the advantages and disadvantages of the use of conventional and green extraction technologies used for the recovery and optimization of the yield of antioxidant naturals are detailed; finally, recent studies on biological properties of antioxidant molecules extracted from plant waste are presented here.