HPLC fingerprinting-based multivariate analysis of phenolic compounds in mango leaves varieties: Correlation to their antioxidant activity and in silico α-glucoidase inhibitory ability

PhInd-Database on Polyphenol Content in Agri-Food By-Products and Waste: Features of the Database

Timely access to topic-relevant datasets is of paramount importance for the development of any successful strategy (food waste reduction strategy), since datasets illuminate opportunities, challenges and development paths. PhInd is the first comprehensive database on polyphenol content in plant-based by-products from the agri-food sector or the wastewater sector and was developed using peer-reviewed papers published in the period of 2015-2021. In total, >450 scientific manuscripts and >6000 compound entries were included. Database inclusion criteria were polyphenol contents = determined using HPLC/UHPLC quantitative methods. PhInd can be explored through several criteria which are either 'open' or checkboxes. Criteria are given in subsections: (a) plant source; (b) by-product industrial processing; (c) pre-treatment of by-products before the isolation of polyphenols; and (d) the extraction step of polyphenols. Database search results could be explored on the website directly or by downloading Excel files and graphs. This unique database content is beneficial to stakeholders-the food industry, academia, government and citizens.

Chemometric Classification of Mangifera indica L. Leaf Cultivars, Based on Selected Phytochemical Parameters; Implications for Standardization of the Pharmaceutical Raw Materials

Introduction

Mangifera indica leaves are among the most common materials employed in manufacturing herbal medicinal products. Despite the phytochemical variation of M. indica cultivars, there are no monographs to guide the cultivation, processing, and authentication of the materials.

Methods

This study characterized 15 Ugandan M. indica leaf varieties, with reference to extraction index (EI), total phenolic content (TPC), antioxidant activity (AOA), and mangiferin concentration (MC). In addition, HPLC fingerprints were established to evaluate the overall phytoequivalence of the materials. Then, using hierarchical clustering (HC) and principal component analysis (PCA), the materials were assigned quality grades.

Results

The mean EI was 9.39 ± 1.64% and varied among the varieties (P=0.001); the TPC varied significantly (P < 0.0001), from 183.29 ± 2.36 mg/g (Takataka) to 79.47 ± 0.58 mg/g (Apple mango). AOA ranged from 16.81 ± 2.85 μg/mL (Doodo red) to 87.85 μg/mL (Asante). MC varied significantly (P < 0.0001), from 105.75 ± 0.60 mg/g (Kate) to 39.53 ± 0.30 mg/g (Asante). HC gave four major grades: A to D (A, varieties with the highest TPC, MC, and AOA). These parameters reduced to below average from group B to group D. The chromatographic fingerprints were visually similar, but the number of peaks varied, from 19 (Kawanda green) to 29 (Kawanda wide), with 23.5 ± 2.9 average peaks. Whole fingerprints were less similar (r < 0.8) than common peak fingerprints (r > 0.9, P < 0.001). PCA grouped the fingerprints into five clusters; loading plots for PC 1 and 2 revealed two important compounds, one at Rt = 15.828 minutes (mangiferin) and the other at 6.021 minutes. Using the standardized common fingerprints, unknown field samples clustered closely with Koona, Kate, and Kawanda green varieties.

Conclusions

The EI, TPC, MC, and AOA values can be utilized to monitor consistency in the quality of materials and the production process. The grades generated can be used to select materials for cultivation and manufacturing. Where minimum concentrations are set, materials of different concentrations are used to dilute or concentrate each other. The HPLC fingerprints can be utilized to authenticate the materials. More samples from different agroecological regions of the country should be tested to cater to climatic variations in order to develop GMP-compliant botanical identification methods.

Inclusion of Natural Antioxidants of Mango Leaves in Porous Ceramic Matrices by Supercritical CO2 Impregnation

Mango is one of the most important, medicinal tropical plants in the world from an economic point of view due to the presence of effective bioactive substances as co-products in its leaves. The aim of this work was to enhance the impregnation of natural antioxidants from mango leaves into a porous ceramic matrix. The effects of pressure, temperature, impregnation time, concentration of the extract and different porous silica on impregnation of phenolic compounds and antioxidant activity were analyzed. The volume of the pressurized fluid extract and amount of porous ceramic matrix remained constant. The best impregnation conditions were obtained at 6 h, 300 bar, 60 mg/mL, 35 °C and with MSU-H porous silica. The results indicated that increasing the pressure, concentration of the extract and temperature during impregnation with phenolic compounds such as gallic acid and iriflophenone 3-C (2-O-p-hydroxybenzolyl)-β-D-glucoside increased the antioxidant activity and the amount of total phenols.

Characterization of phenolics and discovery of α-glucosidase inhibitors in Artemisia argyi leaves based on ultra-performance liquid chromatography-tandem mass spectrometry and relevance analysis

Artemisia argyi leaves (AAL) has been widely used as herbal medicine and food supplement and in China and other Asian countries. The aim of this work is to qualitative and quantitative characterization of phenolic compounds in AAL and screening of natural product inhibitors of α-glucosidase from AAL. Ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS) was employed to rapid and comprehensive identification of phenolic compounds in AAL, and a total of thirty-three phenolic compounds were identified. High performance liquid chromatography with diode array detection (HPLC-DAD) was established and validated to simultaneously determinate ten main bioactive phenolics compounds in different batches of AAL samples. Meanwhile, the inhibitory capacities of different batches of AAL samples on α-glucosidase were evaluated. Then, relevance analysis, including grey relational analysis and Pearson correlation analysis were employed to investigate the correlations between the contents of phenolic compounds and α-glucosidase inhibitory activities, and discover the α-glucosidase inhibitors in AAL. The relevance analysis results indicated that three phenolic compounds, 3-caffeoylquinic acid, 3,4-dicaffeoylquinic acid and 3,5-dicaffeoylquinic acid could be potential α-glucosidase inhibitors in AAL. Moreover, the α-glucosidase inhibitory activities of the three phenolic compounds were validated by in vitro and in vivo experiments. The possible inhibiting effect of the three phenolic compounds on α-glucosidase was also explored by molecular docking analysis, and the results indicated that the binding of the three α-glucosidase inhibitors to α-glucosidase mainly by hydrogen bonds, hydrophobic forces and ionic bonds. The present research provided a deep insight into phenolic compounds and α-glucosidase inhibitory activities of AAL, and discovered the α-glucosidase inhibitors in AAL.

Bio-affinity ultra-filtration combined with HPLC-ESI-qTOF-MS/MS for screening potential α-glucosidase inhibitors from Cerasus humilis (Bge.) Sok. leaf-tea and in silico analysis

Cerasus humilis(Bge.) Sok. leaf-tea (CLT) has a potential anti-α-glucosidase effect. However, its anti-α-glucosidase functional compositions remain unclear. Results showed that 70% methanol extract of CLT (IC₅₀ = 36.57 μg/mL) with the highest total phenolic/flavonoid contents exhibited significantly higher α-glucosidase inhibitory activity (α-GIA) than acarbose (IC₅₀ = 189.57 μg/mL). Additionally, phenolic constituents of the CLT extract were analyzed for the first time in this work. Ten major potential α-glucosidase inhibitors (α-GIs) with high bio-affinity degree in the CLT extract were recognized using a bio-affinity ultra-filtration and HPLC-ESI-qTOF-MS/MS method. In vitro α-GIA assay confirmed that myricetin (IC₅₀ = 36.17 μg/mL), avicularin (IC₅₀ = 69.84 μg/mL), quercitrin, isoquercitrin, prunin and guajavarin were responsible for the α-GIA of the CLT extract. More importantly, the interaction mechanism between α-GIs and α-glucosidase was investigated via in silico analysis. This study provides a high-throughput screening platform for identification of the potential α-GIs from natural products.

Comparison of Various Solvent Extracts and Major Bioactive Components from Unsalt-Fried and Salt-Fried Rhizomes of Anemarrhena asphodeloides for Antioxidant, Anti-α-Glucosidase, and Anti-Acetylcholinesterase Activities

The rhizome of Anemarrhena asphodeloides Bunge (AA, family Liliaceae) is a famous and frequently used herbal drug in the traditional medicine of Northeast Asia, under vernacular name “zhimu”. A. asphodeloides has been used as an anti-inflammatory, antipyretic, anti-platelet aggregation, anti-depressant, and anti-diabetic agent in traditional Chinese medicine. We examined the antioxidant, anti-acetylcholinesterase (AChE), and anti-α-glucosidase activities of various solvent extracts and the main bioactive compounds from the rhizome of A. asphodeloides. Acetone extract exhibited comparatively high antioxidant activities by 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, and ferric-reducing antioxidant power (FRAP) assays. A water extract exhibited relatively strong antioxidant activity by superoxide radical scavenging test. Furthermore, dichloromethane, chloroform, and n-hexane extracts showed significant anti-α-glucosidase activities. Finally, ethanol and dichloromethane extracts exhibited relatively strong AChE inhibitory activity. HPLC analysis was used to examine and compare various solvent extracts for their compositions of isolates. We isolated four major chemical constituents and analyzed their antioxidant, anti-α-glucosidase, and AChE inhibitory activities. The bioactivity assays showed that mangiferin displayed the most potential antioxidant activities via FRAP, ABTS, DPPH, and superoxide assays and also exhibited the most effective anti-AChE and anti-α-glucosidase activities among all the isolates. The present study suggests that A. asphodeloides and its active extracts and components are worth further investigation and might be expected to develop as a candidate for the treatment or prevention of oxidative stress-related diseases, AChE inhibition, and hyperglycemia.

Innovative Biochemometric Approach to the Metabolite and Biological Profiling of the Balkan Thistle (Cirsium appendiculatum Griseb.), Asteraceae

The widespread genus Cirsium Mill. (Asteraceae) is renowned in traditional medicine. In the present study, an innovative biochemometric-assisted metabolite profiling of the flower heads, aerial parts and roots of Cirsium appendiculatum Griseb. (Balkan thistle) in relation to their antioxidant and enzyme inhibitory potential was developed. The workflow combines ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) with partial least-square analysis to discriminate the herbal extracts and identify the most prominent biological activities. The annotation and dereplication of 61 secondary metabolites were evidenced, including 15 carboxylic (including hydroxybenzoic and hydroxycinnamic) acids and their glycosides, 11 acylquinic acids, 26 flavonoids and 9 fatty acids. All compounds were reported for the first time in the studied species. The root extract revealed the highest cupric and ferric reducing power (618.36 ± 5.17 mg TE/g and 269.89 ± 8.50 mg TE/g, respectively) and antioxidant potential in phosphomolybdenum (3.36 ± 0.15 mmol TE/g) as well as the most prominent enzyme inhibitory potential on α-glucosidase (0.72 ± 0.07 mmol ACAE/g), acetylcholinesterase (4.93 ± 0.25 mg GALAE/g) and butyrylcholinesterase (3.80 ± 0.26 mg GALAE/g). Nevertheless, the flower heads were differentiated by their higher metal chelating activity (32.53 ± 3.51 mg EDTAE/g) and total flavonoid content (46.59 ± 0.89 mgRE/g). The partial least-square discriminant and heat-map analysis highlighted the root extract as the most active and a promising source of bioactive compounds for the therapeutic industry.

LC-Q-Orbitrap-MS/MS Characterization, Antioxidant Activity, and α-Glucosidase-Inhibiting Activity With In Silico Analysis of Extract From Clausena Indica (Datz.) Oliv Fruit Pericarps

Clausena indica (Datz.) Oliv fruit pericarps (CIOPs) is an important agro-industrial by-product rich in active components. In this article, the effects of traditional and green deep eutectic solvents (DESs) on the high-performance liquid chromatography (HPLC) characterization, antioxidant activities, and α-glucosidase-inhibitory activity of phenolic extracts from CIOPs were investigated for the first time. The results showed that ChCl-Gly and Bet-CA had higher extraction efficiency for the total phenolic content (TPC, 64.14-64.83 mg GAE/g DW) and total flavonoid content (TFC, 47.83-48.11 mg RE/g DW) compared with the traditional solvents (water, methanol, and ethyl acetate). LC-Q-Orbitrap-MS/MS was adopted to identify the phenolic compositions of the CIOPs extracts. HPLC-diode array detection (HPLC-DAD) results indicated that arbutin, (-)-epigallocatechin, chlorogenic acid, procyanidin B1, (+)-catechin, and (-)-epicatechin were the major components for all extracts, especially for deep eutectic solvents (DESs). In addition, ChCl-Xyl and ChCl-Gly extracts showed higher antioxidant activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH^•), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS^+•), ferric reducing antioxidant power (FRAP), reducing power (RP), and cupric ion reducing antioxidant capacity (CUPRAC) than extracts extracted by other solvents. A strong α-glucosidase-inhibiting activity (IC₅₀, 156.25-291.11 μg/ml) was found in three DESs extracts. Furthermore, in silico analysis of the major phenolics in the CIOPs extracts was carried out to explore their interactions with α-glucosidase. Multivariate analysis was carried out to determine the key factors affecting the antioxidant activity and α-glucosidase-inhibiting activity. In short, DES can be taken as a promising solvent for valorization and recovery of bioactive compounds from agro-industrial by-products. The results verified that CIOPs can be used as a prospective source rich in bio-active compounds applied in the food and pharmacy industries.

Unravelling the Phytochemical Composition and the Pharmacological Properties of an Optimized Extract from the Fruit from Prunus mahaleb L.: From Traditional Liqueur Market to the Pharmacy Shelf

Prunus mahaleb L. fruit has long been used in the production of traditional liqueurs. The fruit also displayed scavenging and reducing activity, in vitro. The present study focused on unravelling peripheral and central protective effects, antimicrobial but also anti-COVID-19 properties exerted by the water extract of P. mahaleb. Anti-inflammatory effects were studied in isolated mouse colons exposed to lipopolysaccharide. Neuroprotection, measured as a blunting effect on hydrogen-peroxide-induced dopamine turnover, was investigated in hypothalamic HypoE22 cells. Antimicrobial effects were tested against different Gram+ and Gram- bacterial strains. Whereas anti-COVID-19 activity was studied in lung adenocarcinoma H1299 cells, where the gene expression of ACE2 and TMPRSS2 was measured after extract treatment. The bacteriostatic effects induced on Gram+ and Gram- strains, together with the inhibition of COX-2, TNFα, HIF1α, and VEGFA in the colon, suggest the potential of P. mahaleb water extract in contrasting the clinical symptoms related to ulcerative colitis. The inhibition of the hydrogen peroxide-induced DOPAC/DA ratio indicates promising neuroprotective effects. Finally, the downregulation of the gene expression of ACE2 and TMPRSS2 in H1299 cells, suggests the potential to inhibit SARS-CoV-2 virus entry in the human host. Overall, the results support the valorization of the local cultivation of P. mahaleb.

Tanacetum vulgare L. (Tansy) as an effective bioresource with promising pharmacological effects from natural arsenal

The Tanacetum genus is a big treasure with the presence of biologically-active compounds and members of this genus are widely used for the treatment of several diseases in traditional medicine system. Considering this fact, we aimed to analyze the extracts from Tanacetum vulgare L. in case of chemical profiles and biological effects. Chemical characterization was performed by using UHPLC-HRMS technique and showed the presence of several phytochemical groups (107 compounds were identified, including phenolic acids, flavonoids, terpenoids and fatty acids. Biological abilities were examined by using antioxidant (DPPH, ABTS, FRAP, CUPRAC, metal chelating and phosphomolybdenum assays) and enzyme inhibition (tyrosinase, amylase, glucosidase and cholinesterase) properties. Pharmaco-toxicological investigations were also performed with the aim to identify limits of biocompatibility, anti-oxidant and neuromodulatory effects, in hypothalamic HypoE22 cells. A bioinformatic analysis was also carried to unravel the putative protein-targets for the observed biological effects. Generally, the tested hexane and hydroalcoholic extracts displayed stronger activities in antioxidant and enzyme inhibitory assays, when compared with water. In addition, multivariate analysis was performed to understand the differences in both solvents and plant parts and we clearly observed the separation of these parameters. The extracts (10 μg/mL) also stimulated DAT and inhibited TNFα and BDNF gene expression, in HypoE22 cells. In parallel, the extracts were also able to stimulate norepinephrine release from this cell line. By contrast, in the concentration range 50-100 μg/mL, the extracts reduced the HypoE22 viability, thus demonstrating cytotoxicity at concentrations 5-10 fold higher compared to those effective as neuromodulatory. Our observations manifested that T. vulgare has several beneficial effects and it can be used as a potential natural raw material for designing further health-promoting applications in nutraceutical, cosmeceutical, and pharmaceutical areas.

Advanced Analytical Approaches for the Analysis of Polyphenols in Plants Matrices—A Review

Phenolic compounds are plants’ bioactive metabolites that have been studied for their ability to confer extensive benefits to human health. As currently there is an increased interest in natural compounds identification and characterization, new analytical methods based on advanced technologies have been developed. This paper summarizes current advances in the state of the art for polyphenols identification and quantification. Analytical techniques ranging from high-pressure liquid chromatography to hyphenated spectrometric methods are discussed. The topic of high-resolution mass spectrometry, from targeted quantification to untargeted comprehensive chemical profiling, is particularly addressed. Structure elucidation is one of the important steps for natural products research. Mass spectral data handling approaches, including acquisition mode selection, accurate mass measurements, elemental composition, mass spectral library search algorithms and structure confirmation through mass fragmentation pathways, are discussed.

Comprehensive evaluation of Licorice extract by five-dimensional quantitative profiling

Licorice extract (LE) is widely used in food and medicine fields. The detection of single chemical component cannot describe its overall quality. In this paper, the content of five active components and HPLC fingerprint of LE was determined. Firstly, the dual-standard system calibration method was proposed to correct the differences between different chromatographic systems. Then, the five-dimensional profiling method (FDPM) was established to evaluate LE based on the five parameters. 52 batches of LE were divided into four categories, Cluster analysis and Orthogonal projections on the latent structure - discrimination analysis (OPLS-DA) showed that the quality and quantity of LE can be reflected by FDPM. In addition, the comparison of different chromatographic system conditions showed that FDPM can dig out the potential information and provide strategies for the monitoring and calibration of fingerprint chromatographic systems.

Mango (Mangifera indica L.) Leaves: Nutritional Composition, Phytochemical Profile, and Health-Promoting Bioactivities

Mangifera indica L. belongs to the family of Anacardiaceae and is an important fruit from South and Southeast Asia. India, China, Thailand, Indonesia, Pakistan, Mexico, Brazil, Bangladesh, Nigeria, and the Philippines are among the top mango producer countries. Leaves of the mango plant have been studied for their health benefits, which are attributed to a plethora of phytochemicals such as mangiferin, followed by phenolic acids, benzophenones, and other antioxidants such as flavonoids, ascorbic acid, carotenoids, and tocopherols. The extracts from mango leaves (MLs) have been studied for their biological activities, including anti-cancer, anti-diabetic, anti-oxidant, anti-microbial, anti-obesity, lipid-lowering, hepato-protection, and anti-diarrheal. In the present review, we have elaborated on the nutritional and phytochemical profile of the MLs. Further, various bioactivities of the ML extracts are also critically discussed. Considering the phytochemical profile and beneficial effects of the MLs, they can be used as a potential ingredient for the development of functional foods and pharmaceutical drugs. However, more detailed clinical trials still needed to be conducted for establishing the actual efficacy of the ML extracts.

Phytochemical Profile and Biological Activities of Crude and Purified Leonurus cardiaca Extracts

Leonurus cardiaca L. (Lamiaceae) is a perennial herb distributed in Asia and Southeastern Europe and has been used in traditional medicine since antiquity for its role against cardiac and gynecological disorders. The polar extracts obtained from L. cardiaca aerial parts contain several compounds among which alkaloids, iridoids, labdane diterpenes, and phenylethanoid glycosides play a major role in conferring protection against the aforementioned diseases. On the other hand, the antioxidant activities and the enzyme inhibitory properties of these extracts have not yet been deeply studied. On the above, in the present study, crude and purified extracts were prepared from the aerial parts of L. cardiaca and have been chemically characterized by spectrophotometric assays and HPLC-DAD-MS analyses. Notably, the content of twelve secondary metabolites, namely phenolic acids (chlorogenic, caffeic, caffeoylmalic and trans-ferulic acids), flavonoids (rutin and quercetin), phenylethanoid glycosides (verbascoside and lavandulifolioside), guanidine pseudoalkaloids (leonurine), iridoids (harpagide), diterpenes (forskolin), and triterpenes (ursolic acid), has been determined. Furthermore, the extracts were tested for their antioxidant capabilities (phosphomolybdenum, DPPH, ABTS, FRAP, CUPRAC, and ferrous chelating assays) and enzyme inhibitory properties against cholinesterase, tyrosinase, amylase, and glucosidase. The purified extracts contained higher phytochemical content than the crude ones, with caffeoylmalic acid and verbascoside as the most abundant compounds. A linear correlation between total phenolics, radical scavenging activity, and reducing power of extracts has been found. Notably, quercetin, caffeic acid, lavandulifolioside, verbascoside, chlorogenic acid, rutin, and ursolic acid influenced the main variations in the bioactivities found in L. cardiaca extracts. Our findings provide further insights into the chemico-biological traits of L. cardiaca and a scientific basis for the development of nutraceuticals and food supplements.