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Binding of Clitoria ternatea L. flower extract with α-amylase simultaneously monitored at two wavelengths using a photon streaming time-resolved fluorescence approach
摘要： The binding of an extract from the flowers of Clitoria ternatea L. to the digestive enzyme α-amylase was investigated. This extract is a mixture of flavonoids, including anthocyanins, and has been previously shown to inhibit the activity this enzyme. This has implications for modulating starch digestion. Since the extract contains a mixture of flavonoids, including anthocyanins, in order to investigate the kinetics, we made use of time-resolved fluorescence to simultaneously monitor two different emission bands emanating from the extract. This measurement was enabled by the use of a “photon streaming” approach and changes in fluorescence lifetime and intensity were used to follow the interaction. A longer wavelength band (655 nm) was ascribed to anthocyanins in the mixture and these were observed to bind at a rate an order of magnitude slower than other flavonoids present in the extract, monitored at a shorter wavelength (485 nm). Changes in the fluorescence emission of the extract upon binding were further assessed by the use of decay associated spectra.
关键词： TCSPC,Butterfly pea,Anthocyanins,Enzyme inhibition,Flavonoids
更新于2025-09-23 15:21:21
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Stress Physiology of Tea in the Face of Climate Change || Molecular and Physiological Adaptations of Tea Plant in Response to Low Light and UV Stress
摘要： The sensory quality, economic value, and health functions of tea liquor depend on several metabolites in leaves of tea (Camellia sinensis L.), such as polyphenols (the most representative quality- and function-related compounds, especially catechins), caffeine, amino acids, aroma compounds, vitamins, and carbohydrates. The biosynthesis of these molecules is significantly affected by both management practices in the field and environmental factors, such as shading and ultraviolet (UV) stress. In this chapter, therefore, we review existing literature reporting the effects of shade and UV irradiances on tea plants with the aim to reappraise morphological, biochemical, physiological, and molecular responses found in this species. Cultivation of tea plants under shade can (i) induce anatomical and ultrastructural adaptations; (ii) influence leaf color, providing characteristic vivid greenness due to incremented chlorophyll content; (iii) decrease the risk of photoinhibition; and finally (iv) improve the quality of tea beverages by causing the reduction of the concentration of phenylpropanoids and caffeine (which contribute to astringency) while increasing the level of amino acids (the compounds that contribute to sweetness). However, the shade practice in tea is still subjected to controversy, and the correct managing of the shade practice is essential. Elevated UV irradiances, especially UV-B, can alter the plant morphology and affect several biochemical and physiological processes; most plant species respond to UV in a dose dependent manner. Protracted exposition to low UV-B doses (similar to UV peaks actually perceive by plants in the ambient) leads to an enhancement of phenylpropanoid metabolism and in particular stimulates the biosynthesis of UV-protecting flavonoids (mainly catechins). Conversely, UV-B doses much higher than those usually experienced in natural environment lead to the downregulation of the phenylpropanoid metabolism likely due to irreversible (to some extent) UV-triggered damages. The understandings of the reactions of tea plants to different light conditions, including situations of low light and high UV, are of pivotal importance to enhance both plant yield and tea quality by “driving” the accumulation of desired compounds in tea leaves.
关键词： Caffeine,UV stress,Amino acids,Low light,Catechins,Flavonoids,Tea plant
更新于2025-09-23 15:21:01
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Simultaneous Quantification of Two Flavonoids in <i>Morus alba</i> by High Performance Liquid Chromatography Coupled with Photodiode Array Detector
摘要： The root bark of Morus alba L. (Family: Moraceae) is an important medicinal herb in many countries and has long been used as a traditional medicine for the treatment of cough, fever, blood pressure reduction, and respiratory diseases. In the present study, the simultaneous determination of two flavonoids, kuwanon G and morusin, for quality control of M. alba was conducted using high-performance liquid chromatography (HPLC) equipped with photodiode array (PDA) detector. The column used for separation of kuwanon G and morusin was a Gemini C18 analytical column maintained at 45°C. The mobile phase for efficient separation of two analytes was flowed 0.1% (v/v) aqueous formic acid–acetonitrile with gradient elution. The detection wavelength for quantification was set at 266 nm. The optimized method showed good linearity with coefficients of determination of 0.9998 within the tested concentration ranges. The limits of detection for the two flavonoids, kuwanon G and morusin, were 0.69 μg/mL and 0.35 μg/mL and the limits of quantification of kuwanon G and morusin, were 2.10 μg/mL and 1.07 μg/mL. The recoveries were 98.40–111.55% and the relative standard deviation (RSD) value was within 3.50%. The RSD values of intra- and interday precisions were 0.08–0.70% and 0.06–0.48%, respectively. The amounts of kuwanon G and morusin were 1.94–2.26 mg/g and 1.05–1.12 mg/g. The established HPLC–PDA method will help to improve the quality control of M. alba and related products.
关键词： Simultaneous quantification,Morus alba,HPLC–PDA,Flavonoids
更新于2025-09-16 10:30:52
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Antioxidant capacity of Camellia japonica cultivars assessed by near- and mid-infrared spectroscopy
摘要： Main conclusion Camellia japonica antioxidant capacity highly differs among its cultivars and could be successfully predicted by near- and mid-infrared spectroscopy. Camellia japonica is a Theaceae family species which are mainly used as an ornamental plant due to its colourful flowers presenting over than 32,000 recognized cultivars. However, this species have been somehow neglected due to the popular tea source, Camellia sinensis. In this study, the antioxidant profile (total phenolic and flavonoid content and total antioxidant capacity—TPC, TFC and TAC) of 31 C. japonica cultivars leaves was determined and further assessed by near- and mid-infrared spectroscopy. The leaves’ antioxidant profile was revealed to be highly dependent on the cultivars analysed being in some cases distinct even for different trees of the same cultivar. Near- and mid-infrared spectroscopy proved to be suitable techniques to predict the total phenolic and flavonoid content as well as the total antioxidant capacity. The best results were obtained with near-infrared spectroscopy whose root mean square error of the prediction set samples was of 5.7?mg of gallic acid/g dry leaf; 3.5?mg catechin/g dry leaf and 3.3?mM Trolox/g dry leaf for TPC, TFC and TAC (with coefficients of the determinations equal to or higher than 0.93). Moreover, the range error ratios were higher than 15 meaning that the developed partial least-squares models are very good for calibration and quantification determinations according to the guidelines for near-infrared models development and maintenance. In this work, the antioxidant profile of several C. japonica cultivars leaves was determined for the first time, being that a rapid and low cost spectroscopic-based method was also proposed for its determination.
关键词： Antioxidants,Camellia japonica cultivars,Chemometrics,Phenolic compounds,Flavonoids,Infrared spectroscopy
更新于2025-09-10 09:29:36
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Enhanced Antioxidant Capacity of Fresh Blueberries by Pulsed Light Treatment
摘要： As a novel technology for food safety risk mitigation, pulsed light (PL) has been shown effective in surface decontamination of fresh blueberries in literature. However, little is known about the effects of PL on the antioxidant capacity and quality characteristics of fresh blueberries. Fresh blueberries from a local farm were treated with PL for 30, 60, 90 and 120 s. Results show that PL exposure enhanced the antioxidant activity (ORAC) and total phenolic content of fresh blueberries 50 and 48% respectively, relative to the control. Pulsed light also significantly increased the total anthocyanin contents, which may be due to the upregulation of Phenylalanine Ammonium Lyase (PAL) enzymes. There was no significant difference (P ≤ 0.05) in the soluble solids, pH, titratable acidity, firmness, color and mass of the fresh blueberries within 120 s PL exposure. In conclusion, PL illumination enhanced the antioxidant capacity of fresh blueberries while maintaining other quality characteristics.
关键词： phenolics,phenylalanine ammonium lyase,phytochemical,nonthermal,flavonoids,anthocyanins
更新于2025-09-09 09:28:46
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Contribution à l’étude de la désinfection de l’eau par photosensibilisation avec des extraits de plantes
摘要： Some plants used in the traditional pharmacopoeia to treat microbial and parasitic infections are able to generate singlet oxygen. This is used to disinfect the water. The study of the disinfection of water by photosensitization with the flavonoid extracts of Aframomum alboviolaceum shows a complete inhibition of fecal coliforms present in the water after one hour of sunshine for the two isolated products by column chromatography of the roots of this plant. Regarding the water samples treated with these two products and kept in the dark, no inhibition was noted from the beginning to the end of the experiments. This suggests that these products are photosensitizers and that in the presence of the sun they undergo photoexcitation which would lead to the formation of singlet oxygen. The latter, once generated, destroys the fecal coliforms present in water.
关键词： Photosensitization,Flavonoids,Singlet oxygen,Aframomum alboviolaceum,Sunstroke time
更新于2025-09-04 15:30:14
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A simple and rapid fluorescent approach for flavonoids sensor based on gold nanoclusters
摘要： The development of simple, easy-to-operate and real-time detection methods for the active ingredients in herbal medicines has aroused growing interest owing to their pivotal health benefits. In this study, a qualitative and quantitative detection method for the flavonoids was developed based on the specific interaction between flavonoids and bovine serum albumin (BSA). A fluorescent gold nanocluster was imbedded into the cavity enclosed in the tertiary structure of BSA, the fluorescence of which can be quenched by the flavonoids with fast response (< 5 s). This decrease in fluorescence intensity of BSA-AuNCs as output signal enables the real-time visual inspection of flavonoids. We demonstrated that the present approach was capable of detecting quercetin in serum, plasma, and monitoring the content of flavonoids in proprietary Chinese medicine Rutin Tablets. BSA-AuNCs was the first fluorescent probe for the specific determination of active ingredients in herbal medicines. Hence the reported protein-AuNCs sensing platform can serve as a convenient detection strategy in pharmaceutical analysis.
关键词： sensor,fluorescence probe,Gold nanoclusters,flavonoids
更新于2025-09-04 15:30:14