Optimization of hydrolysis of rutin in subcritical water using response surface methodology

Sensomics-assisted analysis unravels the formation of the Fungus Aroma of Fu Brick Tea

Fu Brick Tea (FBT) is characterized by Fungus Aroma (FA), which determines the quality of FBT products. However, the aroma constituents and their interactive mechanism for FA remain unclear. In this study, the FBT sample with the optimal FA characteristics was selected from 29 FBTs. Then, 19 components with OAV ≥ 1 were identified as the odorants involved in the FA formation. The aroma recombination test suggested that the FA was potentially produced by the synergistic interplay among the 15 key odorants, including (E,E)-2,4-heptadienal, (E,E)-2,4-nonadienal, (E)-2-nonenal, (E,Z)-2,6-nonadienal, (E)-2-octenal, (E)-β-ionone, 4-ketoisophorone, dihydroactinidiolide, (E)-β-damascenone, 1-octen-3-ol, linalool, geraniol, heptanal, hexanal, and phenylacetaldehyde. And, the synergistic effects between them were preliminarily studied by aroma omissions, such as modulatory effects, masking effects, compensatory effects, and novelty effects, ultimately contributing to the FA. In all, this work helps us better understand the formation of the FA and provides a basis for the improvement of FBT production technology.

Teucrium montanum L.-Unrecognized Source of Phenylethanoid Glycosides: Green Extraction Approach and Elucidation of Phenolic Compounds via NMR and UHPLC-HR MS/MS

Health-oriented preferences, a demand for innovative food concepts, and technological advances have greatly influenced changes in the food industry and led to remarkable development of the functional food market. Incorporating herbal extracts as a rich source of bioactive compounds (BC) could be an effective solution to meet the high demand of consumers in terms of expanding the high-quality range of functional foods. The aim of this study is the valorization of the bioactive potential of T. montanum L., an understudied Mediterranean plant species, and the in-depth elucidation of a polyphenolic profile with a UHPLC-HR MS/MS and NMR analysis. The total phenolic content (TPC) and antioxidant capacity (AC) were determined on heat-assisted (HAE), microwave-assisted (MAE) and subcritical water (SWE) extracts. In terms of antioxidant capacity, SWE extracts showed the most notable potential (ABTS: 0.402-0.547 mmol eq Trolox g-1 dw, DPPH: 0.336-0.427 mmol eq Trolox g-1 dw). 12 phenolic compounds were identified in the samples of T. montanum from six microlocations in Croatia, including nine phenylethanoid glycosides (PGs) with total yields of 30.36-68.06 mg g-1 dw and 25.88-58.88 mg g-1 dw in HAE and MAE extracts, respectively. Echinacoside, teupolioside, stachysoside A, and poliumoside were the most abundant compounds HAE and MAE extracts, making T. montanum an emerging source of PGs.

Hydrothermal treatment improves xanthine oxidase inhibitory activity and affects the polyphenol profile of Flos Sophorae Immaturus

BACKGROUND

Flos Sophorae Immaturus (FSI) is rich in polyphenols and a potential uric acid-lowering food. However, the processing of FSI is greatly restricted due to the heat sensitivity and low solubility of polyphenols. In this study, hydrothermal treatment - an effective strategy - was applied to FSI processing. The variation of xanthine oxidase (XO) inhibitory effect and polyphenol composition of FSI during hydrothermal treatment were recorded.

RESULTS

The XO inhibition rate of FSI increased from 32.42% to 89.00% after hydrothermal treatment at 220 °C for 30 min, as well as total polyphenols (from 0.66 to 1.11 mg mL^-1 ) and flavonoids (from 1.21 to 1.58 mg mL^-1 ). However, high thermal temperature (>160 °C) and extended thermal time (>90 min) caused the degradation of polyphenols. Rutin, kaempferol-3-O-rutinoside and narcissoside rapidly degraded and converted to quercetin, kaempferol and isorhamnetin when the temperature exceeded 160 °C. The maximum yields of quercetin, kaempferol and isorhamnetin were at 220 °C for 30 min, 90 min and 90 min, respectively. Meanwhile, the conversion kinetics conformed to the first-order model. Interestingly, these newly formed polyphenols possessed better XO inhibitory effects than their derivatives with 3-O-rutinoside.

CONCLUSION

Polyphenol conversion during hydrothermal treatment was the main reason for enhancing XO inhibitory activity. Therefore, hydrothermal treatment is an appropriate method for improving the XO inhibitory effect of FSI. © 2022 Society of Chemical Industry.

Recent trends in extraction of plant bioactives using green technologies: A review

Phenolic compounds from plant sources have significant health-promoting properties and are known to be an integral part of folk and herbal medicines. Consumption of phenolics is known to alleviate the risk of various lifestyle diseases including cancer, cardiovascular, diabetes, and Alzheimer's. In this context, numerous plant crops have been explored and characterized based on phenolic compounds for their use as supplements, nutraceutical, and pharmaceuticals. The present review highlights some important source of bioactive phenolic compounds and novel technologies for their efficient extraction. These techniques include the use of microwave, ultrasound, and supercritical methods. Besides, the review will also highlight the use of response surface methodology (RSM) as a statistical tool for optimizing the recoveries of the phenolic bioactives from plant-based matrices.

Extraction of flavanones from immature Citrus unshiu pomace: process optimization and antioxidant evaluation

Dietary guidelines recommend the consumption of flavonoid-rich extracts for several health benefits. Although immature Citrus unshiu pomace (ICUP) contains high levels of flavanone glycosides, many studies have concentrated on the optimization of flavonoid extraction from mature citrus peels. Therefore, we developed an optimized extraction method for hesperidin and narirutin from ICUP, and evaluated their antioxidant activities using ten different assay methods. The extraction conditions for the highest flavonoid yields based on a response surface methodology were 80.3 °C, 58.4% (ethanol concentration), 40 mL/g (solvent/feed), and 30 min, where the hesperidin and narirutin yields were 66.6% and 82.3%, respectively. The number of extractions was also optimized as two extraction steps, where the hesperidin and narirutin yields were 92.1% and 97.2%, respectively. Ethanol was more effective than methanol and acetone. The ethanol extract showed high scavenging activities against reactive oxygen species but relatively low scavenging activities for nitrogen radicals and reactive nitrogen species. The antioxidant activities showed a higher correlation with hesperidin content than narirutin content in the extracts. This study confirms the potential of an optimized method for producing antioxidant-rich extracts for the functional food and nutraceutical industries.

Ultrasound processing of rutin in food-grade solvents: Derivative compounds, antioxidant activities and optical rotation

The effect of ultrasound was studied on the flavonoid rutin to understand its hydrolysis to aglycones, antioxidant capacity and optical rotation. The total phenolic content increased >56% at 3.6-36 kJ/cm³, indicating production of phenolic compounds. In the water media, at 27 kJ/cm³ and 47 °C, the total flavonoid content increased from control 0.26 ± 0.01 to 0.45 ± 0.02 mg catechin equivalent/mg rutin hydrate. Quercetin yield in citric acid media increased with change in energy density from 0.34 ± 0.09% at 0.1 kJ/cm³ (68 °C) to 2.23 ± 0.04% at 7.0 kJ/cm³ (86 °C). A plummeting effect was only observed in water media after 27 kJ/cm³ by FRAP (47 °C) and DPPH (86 °C) antioxidant activities, indicating that the presence of solutes (citric acid and NaCl) after 27 kJ/cm³ reduced degradation of flavonoids. Furthermore, ultrasonication increased levorotatory rutin enantiomers, that can be used to further modify physico-chemical properties of other food components.

Semi-Continuous Subcritical Water Extraction of Flavonoids from Citrus unshiu Peel: Their Antioxidant and Enzyme Inhibitory Activities

We extracted and hydrolyzed bioactive flavonoids from C. unshiu peel using subcritical water (SW) in a semi-continuous mode. The individual flavonoid yields, antioxidant and enzyme inhibitory activities of the SW extracts were analyzed. The extraction yields of hesperidin and narirutin increased with increasing temperature from 145 °C to 165 °C. Hydrothermal hydrolysis products (HHP), such as monoglucosides (hesperetin-7-O-glucoside and prunin) and aglycones (hesperetin and naringenin) were obtained in the SW extracts at temperatures above 160 °C. The sum of hesperidin and its HHP in the SW extracts was strongly correlated with antioxidant activities, whereas the contents of hesperetin and naringenin were strongly correlated with enzyme inhibitory activities. Hesperetin exhibited the highest antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ferric-reducing antioxidant power, and oxygen radical absorbance capacity), whereas hesperetin-7-O-glucoside exhibited the highest enzyme inhibitory activities (angiotensin-І converting enzyme (ACE) and pancreatic lipase (PL)). Naringenin exhibited the highest enzyme inhibitory activities (xanthine oxidase and α-glucosidase). PMFs (sinensetin, nobiletin, and tangeretin) also exhibited relatively high inhibitory activities against ACE and PL. This study confirms the potential of SW for extracting and hydrolyzing bioactive flavonoids from C. unshiu peel using an environmentally friendly solvent (water) and a shorter extraction time.

Valorization of Yarrow (Achillea millefolium L.) By-Product through Application of Subcritical Water Extraction

In the present study, valorization of yarrow (Achillea millefolium) by-product from the filter tea industry was investigated through the application of subcritical water for the extraction of bioactive compounds. The influence of different process parameters (temperature 120-200 °C, extraction time 10-30 min, and HCl concentration in extraction solvent 0-1.5%) on extract quality in terms of content of bioactive compounds and antioxidant activity was investigated. Optimal conditions of the extraction process (temperature 198 °C, extraction time 16.5 min, and without acidifer) were determined and, when applied, the most efficient exploitation of by-products is achieved, that is, attainment of extracts rich in total phenols and flavonoids and high antioxidant activity. In addition, by applying the high performance liquid chromatographic analysis, the content of chlorogenic acid was determined as well as the hydroxymethylfurfural content in obtained extracts. The results demonstrated that subcritical water can be successfully used for utilization of yarrow by-products for obtaining extracts rich in antioxidants.

Pilot-scale subcritical-water extraction of nodakenin and decursin from Angelica gigas Nakai

Active components were extracted from Angelica gigas Nakai by subcritical-water extraction (SWE) with the purpose of determining how the extraction conditions affect the SWE of antioxidant properties and active components (nodakenin and decursin), and to compare pilot-scale SWE (8 L) and conventional extraction methods. The extraction yields of nodakenin and decursin in the pilot-scale system were highest at 150 °C for 10 min and 190 °C for 15 min, respectively. The extraction yield of decursin increased as the stirring speed was increased to 200-250 rpm. Pearson's correlation indicated that the radical-scavenging activities using DPPH and ABTS assays were more sensitive to the Maillard reaction (R² = 0.822 and 0.933, respectively) than to the total phenolic contents (R² = 0.486 and 0.724, respectively). The extraction yield of decursin was higher when using conventional extraction methods than for SWE.

Subcritical water extraction of polyphenolic compounds from sorghum (Sorghum bicolor L.) bran and their biological activities

Subcritical water extraction (SWE), an environment-friendly technique, was applied to extract polyphenolics from sorghum bran. Extraction temperatures (°C), time (min), and solid-liquid ratio (mL/g) were investigated and optimized by Box-Behnken design. The optimized conditions for SWE was 144.5 °C of temperature, 21 min of time, and 35 mL/g of solid-liquid ratio, with a polyphenolics yield of 47.253 ± 0.375 mg GAE/g dw, which was in good agree with the predicted value. Comparing with hot water extraction (HWE), SWE resulted in a higher yield of polyphenolics, higher radical scavenging activities, and more efficient antiproliferative activity. Furthermore, major polyphenolic compositions of the extracts were identified and quantified by HPLC-ESI-MS/MS. Taxifolin, taxifolin hexoside, oligomeric procyanidins, and epicatechin were the most abundant polyphenolic compounds in the extracts. Taken together, SWE can be used as a effective extraction method for polyphenolics from sorghum bran, which could be used as a potential source of natural antioxidants.

Optimization of Subcritical Water Hydrolysis of Rutin into Isoquercetin and Quercetin

Maximum production of isoquercetin and quercetin simultaneously from rutin by subcritical water hydrolysis (SWH) was optimized using the response surface methodology. Hydrolysis parameters such as temperature, time, and CO₂ pressure were selected as independent variables, and isoquercetin and quercetin yields were selected as dependent variables. The regression models of the yield of isoquercetin and quercetin were valid due to the high F-value and low P-value. Furthermore, the high regression coefficient indicated that the polynomial model equation provides a good approximation of experimental results. In maximum production of isoquercetin from rutin, the hydrolysis temperature was the major factor, and the temperature or time can be lower if the CO₂ pressure was increased high enough, thereby preventing the degradation of isoquercetin into quercetin. The yield of quercetin was considerably influenced by temperature instead of time and CO₂ pressure. The optimal condition for maximum production of isoquercetin and quercetin simultaneously was temperature of 171.4°C, time of 10.0 min, and CO₂ pressure of 11.0 MPa, where the predicted maximum yields of isoquercetin and quercetin were 13.7% and 53.3%, respectively. Hydrolysis temperature, time, and CO₂ pressure for maximum production of isoquercetin were lower than those of quercetin. Thermal degradation products such as protocatechuic acid and 2,5-dihydroxyacetophenone were observed due to pyrolysis at high temperature. It was concluded that rutin can be easily converted into isoquercetin and quercetin by SWH under CO₂ pressure, and this result can be applied for SWH of rutin-rich foodstuffs.

Hydrothermal Degradation of Rutin: Identification of Degradation Products and Kinetics Study

The model glycoside compound quercetin-3-O-rutinoside (rutin) was subjected to subcritical water within the temperature range of 120-220 °C, and the hydrothermal degradation products were analyzed. Two kinetic models describing the degradation of this compound in two different atmospheres (N₂ and CO₂), used for pressure establishment in the reactor, have been developed and compared. Reaction was considered a successive one with three irreversible steps. We confirmed that rutin degradation to quercetin follows first-order kinetics. At higher temperatures quercetin is further degraded in two degradation steps. Formations of 3,4-dihydroxybenzoic acid and catechol were described with the zero-order kinetic models. Reaction rate constants for hydrolysis of glycoside to aglycone in a CO₂ atmosphere are higher compared to those in a N₂ atmosphere, whereas at higher temperatures reaction rate constants for further two successive reactions of aglycone degradation are slightly lower in the presence of CO₂. The difference in reaction activation energies is practically negligible for both gases. Furthermore, degradation products of sugar moieties, that is, 5-hydroxymethylfurfural and 5-methylfurfural, were also detected and analyzed.