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Plant phenolic compounds demonstrate bioactive properties in vitro and/or in vivo, which creates demand for their precise determination in life sciences and industry. Measuring the concentration of individual phenolic compounds is a complex task, since approximately 9000 plant phenolic substances have been identified so far. The determination of the total phenolic content (TPC) is less laborious and is used for the qualimetric evaluation of complex multicomponent samples in routine analyses. Biosensors based on phenol oxidases (POs) have been proposed as alternative analytical devices for detecting phenolic compounds; however, their effectiveness in the analysis of food and vegetal matrices has not been addressed in detail. This review describes catalytic properties of laccase and tyrosinase and reports on the enzymatic and bienzymatic sensors based on laccase and tyrosinase for estimating the total phenolic index (TPI) in food-related samples (FRSs). The review presents the classification of biosensors, POs immobilization, the functions of nanomaterials, the biosensing catalytic cycle, interference, validation, and some other aspects related to TPI assessment. Nanomaterials are involved in the processes of immobilization, electron transfer, signal formation, and amplification, and they improve the performance of PO-based biosensors. Possible strategies for reducing interference in PO-based biosensors are discussed, namely the removal of ascorbic acid and the use of highly purified enzymes.

Pharmaceutical plants contain several phytochemicals that are sources of myriad biological activities. These biological activities can be explored in multiple fields for the benefit of mankind. Pharmaceutical plants with high ethnobotanical indices (i.e., use value and relative frequency of citation) were reported with the potential to inhibit lettuce elongation through leachates and volatiles. The focus of the study was to assess Chinese pharmaceutical plants for both antioxidants, as well as allelopathic potentials to explore any underlying relationship. The estimation of antioxidative capacity and content of total phenolics (TPC) for the 55 Chinese pharmaceutical plants was conducted by the assays of DPPH radical scavenging activity (DPPH-RSA), oxygen radical absorbance capacity (ORAC) and the means of Folin–Ciocalteu. The estimation of the activity of allelopathy for collected medicinal plants was done by adopting the sandwich method for plant leachates and the dishpack method for volatile constituents, respectively. The fruits of sea buckthorn (Hippophae rhamnoides) had the most remarkable ORAC value (168 ± 7.04 μmol TE/g) and DPPH radical scavenging activity (440 ± 7.32 μmol TE/g) and contained the highest contents of total phenolic compounds (236 ± 7.62 mg GAE/g) in the 55 pharmaceutical plant species according to the results. In addition, sea buckthorn showed dominant allelopathic potential through plant leachates evaluated by using the sandwich method. Star anise (Illicium verum Hook. f.) showed conspicuous allelopathic activity through plant volatiles assessed by the dishpack bioassay method. Among the same plant species, antioxidative ability and total phenolics, in comparison with potential allelopathy of medicinal herbs indicated that volatile allelochemical had a weak active effect (r = 0.407 to 0.472, p < 0.01), with antioxidant capacity by the dishpack method. However, the evaluation by the sandwich method showed a significant positive correlation (r = 0.718 to 0.809, p < 0.001) with antioxidant capacity. Based on these results, a new hypothesis is that the antioxidant activity of plants may have an involvement with the potential allelopathic activity.

The aim of the study was to optimize the extraction of bioactive compounds from Clitoria ternatea L. followed by its encapsulation by ionic gelation. The extraction of the bioactive compounds, using water as solvent, was carried out with solid-liquid extractions at hot and room temperature, obtaining as a response factor the content of total phenolic compounds (TPC). The bioactive compounds of the extracts were evaluated based on the levels of TPC and total monomeric anthocyanins. Analyzes of physical, chemical, phytochemical and antioxidant potential were performed. Encapsulation was performed by ionic gelation. The capsules were evaluated by characterization and visual aspects. Simulated gastrointestinal digestibility was determined based on TPC bioaccessibility. There was no statistical difference (p ? 0.05) between the extracts. The quadratic mathematical model presented a correction coefficient, R² = 0.997 and R²adjust = 0.974. Hot extraction at 80°C 5 minutes-1 at a concentration of 0.008 g mL-1 showed a TPC of 23.91 ± 0.90 mg (EGA) g-1 and 0.97 ± 0.50 mg (MVE) g-1 for monomeric anthocyanins. For antioxidant potential, the values of ABTS, FRAP and ?-carotene/linoleic acid were 84.86 ± 1.52 µM trolox g-1, 220.83 ± 3.69 µM ferrous sulfate g-1 and 55, 95 ± 4.51%, respectively, for the same assay. The capsules had regular sizes and preserved color, high solubility (99%), encapsulation efficiency (76%). Bioaccessibility was 71% for lyophilized capsules, with greater intestinal absorption. Therefore, extracts and capsules of Clitoria ternatea L. possess bioactive compounds with an antioxidant profile.

Lychnis flos-cuculi L., a species with potential medicinal value, contains flavonoids, phenolic acids, triterpenoid saponins and ecdysteroids. In this study, the antioxidant activity of plant material of L. flos-cuculi obtained from in vitro cultures compared to that of intact plants from the natural site has been evaluated for the first time. Phytochemical screening of the in-vitro-derived material by ultra-high-performance liquid chromatography mass spectrometry (UHPLC-MS) confirmed the presence of the aforementioned metabolite classes. The aqueous methanolic extracts from in-vitro-derived plant material and the organs of intact plants were analyzed using spectrophotometric methods to quantify total phenolics, phenolic acids and flavonoids, and determine the preliminary antioxidant activity by ferric reducing antioxidant potential (FRAP) and DPPH radical scavenging activity assays. The results showed that the inflorescence (Ns-F), and flowering herb of both plants gathered from natural habitat (Ns-H) and in-vitro-derived plants from the experimental plot (ExV-H) are the materials richest in polyphenols (195.4, 113.47, 112.1 mg GAE g−1 d.w., respectively), and demonstrate the highest antioxidant activity (20.14, 11.24, and 11.46 mg AAE g−1 d.w.). The extract from callus exhibited the lowest polyphenol content and antioxidant potential. The contents of total phenolics, flavonoids and phenolic acids correlate with the results of the antioxidant capacity of L. flos-cuculi extracts.

Polyphenols are strong antioxidants of plant origin that exhibit protective role against the development of several chronic degenerative diseases. Quantitative data on the content of polyphenolic antioxidants in Bulgarian medicinal plants are sporadic and unsystematic.The aim of the study is to determine polyphenols content in series of extracts, infusions and decocts of selected Bulgarian medicinal plants and fruits and to compare their polyphenolic profile.Materials and Methods: In the present study 18 Bulgarian medicinal plants and fruits have been analyzed for Total Phenolic and Total Flavonoids content, along with HPLC analysis for their level of the individual flavonoids (+)-Catechin, (-)-Epicatechin and Rutin. Comparative evaluation of the content of antioxidant polyphenolic compounds was performed by hierarchical cluster analysis.The results show that infusions of Hawthorn (Crategus monogyna) flowers have the highest values of Total Phenolic and Total Flavonoids content, forming a separate Cluster in the analysis of the Agglomeration schedule coefficients. Within fruits, data for Total Phenolics and Total Flavonoids content are more homogenic as the cluster analysis shows distribution of 6 elements in a high mean value group. Elderberry (Sambicus nigra) flowers and fruits are the richest source of Rutin in the selected plants studied.Conclusion: In the present study new data for polyphenolic content in selected Bulgarian medicinal plants and fruits are presented and their degree of similarity in methanolic extracts, infusions and decocts have been assessed in order to provide new data for development of effective antioxidant medicinal plant compositions.

The (Mill.) is an important medicinal plant found in tropical and warm areas, and is known for its application in the food, cosmetic, and pharmaceutical industries. However, no information is available regarding its chemical composition, total phenolics and antioxidant potential. Thus, the present study aimed to investigate the total phenolic and flavonoid contents and their antioxidant potential through insilico studies. The ethanolic extracts were characterized by high-pressure liquid chromatography (HPLC) and UV-visible spectroscopy. Seventeen peaks were detected based on UV- spectroscopy. Furthermore, molecular docking of major phenolic compounds was carried out using Autodock Vina Software against human peroxiredoxin 5 (PDB ID: 1HD2) to study its antioxidant potential. Further, ADME predictions were made to determine physiochemical characteristics of the lead compound. The total phenolic and flavonoid contents of (Mill.) ethanolic extracts were 311.74 and 208.2 mg/g respectively. Molecular docking results showed that dicaffeoylquinic acid (docking score -7.8) has significant binding potential against human peroxiredoxin 5 (PDB ID: 1HD2). ADME and drug likeness parameters have also shown that dicaffeoylquinic acid can be used as a potential antioxidant candidate compared to synthetic antioxidant drugs with side effects. The results of this study underscore the therapeutic potential of (Mill.), warranting further investigation into its bioactive compounds for potential applications in pharmaceuticals and nutraceuticals. Future research should focus on exploring the mechanisms and efficacy of these compounds in clinical settings, paving the way for the development of novel therapeutic agents derived from this medicinal plant.

Syzygium malaccense belongs to the family Myrtaceae and it is popularly recognised as ‘jambo’ in Brazil. It is poorly studied regarding the bioactive compounds of fruits and leaves. This study aimed at optimizing the extraction and characterization of bioactives compounds from S. malaccense leaves. Extraction was optimized using a 23 full factorial design to evaluate the effect of ethanol concentration, time and temperature on polyphenols and antioxidants contents. Analyses of phenolic compounds content (Folin-Ciocalteau and HPLC-DAD), in vitro antioxidant capacities (DPPH, ABTS and FRAP), antimicrobial activity against bacteria and yeasts of ethanolic extract was carried out in optimal conditions of extraction. The optimized extraction condition was 45 min., 80°C and 40:60 (v v-1) ethanol:water. The extract showed high total phenolic content (0.074 mg GAE kg-1), DPPH (0.666 μmol TE kg-1) and ABTS (0.853 μmol TE kg-1) free radical scavenging ability and appreciable ferric reducing power (1.267 μmol Fe2+ kg-1). HPLC methodology allowed the identification of four bioactive compounds: gallic acid (0.00036 mg kg-1), catechin (0.00021 mg kg-1), rutin (0.00027 mg kg-1) and quercetin (0.00003 mg kg-1). The extract showed inhibitory activity against S. aureus (1 µg L-1); S. bongori (8 µg L-1), C. albicans and C. tropicalis (2 µg L-1). It also showed microbicidal potential against S. aureus; C. albicans and C. tropicalis.

Perilla is herbaceous plant, functional food, and nutraceutical product with antioxidant properties. The objective of this study was to investigate the growth, reflectance indices, and antioxidant properties of P. frutescens species in response to fertilizer and salicylic acid (SA) applications. Two independent experiments were carried out in an environmentally controlled greenhouse: (1) pots of red-leaf and green-leaf cultivars divided into four groups treated with 10-30-20 (10N-13.1P-16.6K), 15-10-30 (15N-4.4P-24.9K), 20-20-20 (20N-8.7P-16.6K), and 30-10-10 (30N-4.4P-8.3K) fertilizers for periods of 10 weeks, and (2) pots of red and green Perilla cultivars divided into five groups treated with 0 (control), 125, 250, 500, and 1,000 µM of SA for periods of 7 weeks. Wide variations occurred in the agronomic performance, soil-plant analysis development (SPAD) value, adjusted normalized difference vegetation index (NDVI), maximal quantum yield of PSII photochemistry (Fv/Fm), and antioxidant activity of the two Perilla varieties. All the measured traits were higher in green than in red Perilla under identical fertilizing, and all agronomic traits in green and red Perilla plants subjected to 125 and 500 μM SA were better than in controls. The SPAD and NDVI values of all plants increased as N% increased, the lowest Fv/Fm values of all plants were observed under 15-10-30 fertilizer treatment, the lowest NDVI values were detected in controls, and the Fv/Fm values of all plants decreased under 1,000 μM SA treatment. These indices can be used as indicators to characterize the physiology of these plants and are suitable for evaluating their growth and development under specific fertilizer and SA treatments. Green Perilla leaf extract (PLE) contained higher rosmarinic acid (RA) concentration in each fertilizer treatment, and higher total phenolic (TP) and RA concentration in each SA treatment. However, red PLE contained higher caffeic acid (CA) concentration than green PLE in each fertilizer and SA treatment, implying that their two genotypes exhibited different abilities and specificities of photosynthetic metabolites, and that different varieties may prepare for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity by up-regulating TP, RA, and CA concentration differently. Thus, Perilla plants can be used as health foods due to high TP, RA, and CA concentration. To produce Perilla efficiently in industrial applications, we undertook to determine the optimum N-P-K fertilizer ratio and SA application for maximizing the growth and accumulation of TP, RA, and CA in Perilla plants.

To cope with environmental harmful conditions, plant cells developed adaptive strategy that involves production of a wide variety of complex secondary metabolites. The spectrum and quantity of biosynthesized compounds in specific plant species is determined by its genotype, tissue, developmental and physiological stage and environmental factors. This phenomenon was used to exploit the potential of anatomical and hairy root cultures of Rindera graeca to produce bioactive compounds. Cultivated in vitro roots were subjected to abiotic stresses i.e., drought or coldness. Next the extract profiling was performed using HPLC-PDA-ESI-HRMS method, as well quantitative determination of caffeic, rosmarinic and lithospermic B acids, that were present in all root extracts. Phenolic acids, flavonoids and iridoids represent the major groups of compounds detected in chemical profiles growing under various conditions roots. The highest number of phytochemicals was determined in roots subjected to coldness. Lithospermic B acid proved to be the most abundant compound in all investigated extracts. Among applied abiotic stress factors it was demonstrated that coldness affected to the most secondary metabolites production. The results of current study suggest that root cultures of R. graeca could serve as a new and abundant source of lithospermic B acid.

Heating effect on total phenol, flavonoids, antioxidant activity, and sugar content of six onion varieties has been quantitatively investigated to explore the effect of different temperatures. The onion varieties comprised one red-skinned variety, two white-skinned varieties, and three yellow-skinned varieties. The heating temperature was scanned at 80°C, 100°C, 120°C, and 150°C for 30 minutes each, and quantitative analysis was performed relative to the powdered onion at ambient temperature. Quercetin, glucosides and sugar content were analyzed using high-performance liquid chromatography. The total phenolic and antioxidant content increased in all six varieties. The total flavonoid levels showed a considerable change. On heating the onion samples at 120°C for 30 minutes, the red-skinned variety showed the highest level of total phenolic content [13712.67 ± 1034.85 μg of gallic acid equivalent/g dry weight (μg GAE/g DW)] and total flavonoids [3456.00 ± 185.82 μg of quercetin equivalents/g dry weight (μg Q/g DW)], whereas the content of total phenolics and total flavonoids were 13611.83 ± 341.61 μg GAE/g DW and 3482.87 ± 117.17 μg Q/g DW, respectively, for the yellow-skinned (Sunpower) variety. Quercetin and its glucoside contents increased up to 120°C and then decreased at 150°C, whereas the sugar content continuously decreased with heating. All cultivars showed the same pattern in the heating effect, and the predominant flavonoids were destroyed at higher temperatures. Therefore, it is improper to expose onion powder to a temperature higher than 120°C.