1H HR-MAS NMR-based metabolomics study of different persimmon cultivars (Diospyros kaki) during fruit development

HR-MAS DREAMTIME NMR for Slow Spinning ex Vivo and in Vivo Samples

HR-MAS NMR is a powerful tool, capable of monitoring molecular changes in intact heterogeneous samples. However, one of the biggest limitations of 1H NMR is its narrow spectral width which leads to considerable overlap in complex natural samples. DREAMTIME NMR is a highly selective technique that allows users to isolate suites of metabolites from congested spectra. This permits targeted metabolomics by NMR and is ideal for monitoring specific processes. To date, DREAMTIME has only been employed in solution-state NMR, here it is adapted for HR-MAS applications. At high spinning speeds (>5 kHz), DREAMTIME works with minimal modifications. However, spinning over 3-4 kHz leads to cell lysis, and if maintaining sample integrity is necessary, slower spinning (<2.5 kHz) is required. Very slow spinning (≤500 Hz) is advantageous for in vivo analysis to increase organism survival; however, sidebands from water pose a problem. To address this, a version of DREAMTIME, termed DREAMTIME-SLOWMAS, is introduced. Both techniques are compared at 2500, 500, and 50 Hz, using ex vivo worm tissue. Following this, DREAMTIME-SLOWMAS is applied to monitor key metabolites of anoxic stress in living shrimp at 500 Hz. Thus, standard DREAMTIME works well under MAS conditions and is recommended for samples reswollen in D2O or spun >2500 Hz. For slow spinning in vivo or intact tissue samples, DREAMTIME-SLOWMAS provides an excellent way to target process-specific metabolites while maintaining sample integrity. Overall, DREAMTIME should find widespread application wherever targeted molecular information is required from complex samples with a high degree of spectral overlap.

Characterization of Bioactivity of Selective Molecules in Fruit Wines by FTIR and NMR Spectroscopies, Fluorescence and Docking Calculations

Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopies were applied to characterize and compare the chemical shifts in the polyphenols' regions of some fruit wines. The obtained results showed that FTIR spectra (1800-900 cm-1) and 1H NMR (δ 6.5-9.3 ppm) of different fruit wines can be used as main indices of the year of vintage and quality of fruit wines. In addition to the classical determination of antioxidant profiles and bioactive substances in wines, fluorometric measurements were used to determine the interactions of wine substances with the main human serum proteins. The results showed relatively high binding properties of wines with the highest one for pomegranate, followed by kiwifruit and persimmon wines. The interactions of vitamin C, catechin and gallic acid with human serum albumin (HSA) were also examined by docking studies. The docking calculations showed that gallic acid has a stronger binding affinity compared to catechin and vitamin C. The stronger binding affinity of gallic acid may be due to three hydrogen bonds and pi-pi interactions. The fluorescence and docking studies proved that only the bioactive compounds of wines and not the amount of alcohol have high binding properties to human serum proteins. The emphasis in this report was made on the utility of FTIR, NMR and fluorescence of wines as a mean of wine authentication and its fingerprint. The findings, based on polyphenols from fruits and fruit wines, their bioactivity and health properties, offer valuable insights for future endeavours focused on designing healthy food products.

Green Technologies for Persimmon By-Products Revalorisation as Sustainable Sources of Dietary Fibre and Antioxidants for Functional Beverages Development

The use of green technologies such as ultrasound and natural deep eutectic solvents (NADES) for revalorisation of food and agricultural by-products represents a sustainable way to tackle waste and promote a healthier environment while delivering much-needed functional food ingredients for an increasingly unhealthy population. The processing of persimmon (Diospyros kaki Thunb.) generates large amounts of by-products rich in fibre-bound bioactive phytochemicals. This paper assessed the extractability of bioactive compounds through NADES and the functional properties of the persimmon polysaccharide-rich by-products to evaluate their suitability to be used as functional ingredients in commercial beverages. Although higher amounts of carotenoids and polyphenols were extracted after eutectic treatment vs. conventional extraction (p < 0.05), the fibre-bound bioactives remained abundant (p < 0.001) in the resulting persimmon pulp by-product (PPBP) and persimmon pulp dietary fibre (PPDF), showing also a strong antioxidant activity (DPPH^•, ABTS^•+ assays) and an improved digestibility and fibre fermentability. The main structural components of PPBP and PPDF are cellulose, hemicellulose and pectin. PPDF-added dairy-based drink showed more than 50% of preference over the control among panellists and similar acceptability scores to the commercial ones. Persimmon pulp by-products represent sustainable source of dietary fibre and bioactives and are suitable candidates to develop functional ingredients for food industry applications.

1H NMR-based metabolic profile and chemometric analysis for the discrimination of Passiflora species genotypic variations

The species of the genus Passiflora (Passifloraceae family) have been used as food, cosmetic and traditional herbal. As a result, the Passiflora species are widely cultivated and has an economic, medicinal and ornamental importance. The popular designation as "passion fruit" and chemical profile of several Passiflora species remains unknown. The lack of chemical information contributes to the erroneous classification and adulteration. In recent years, special attention has been paid to the bioactivity and phytochemical profiles of several Passiflora species extracts. In this research, ¹H NMR-based metabolic profiling coupled with chemometric tools was used to characterize and distinguish extracts obtained from different wild Passiflora species (P. alata, P. cincinnata, and P. setacea) and genetic varieties (P. alata var. BRS Pérola do Cerrado, P. cincinnata var. BRS Sertão Forte, and P. setacea var. BRS Pérola do Cerrado). Fourteen metabolites were identified by 1D and 2D NMR experiments, highlighting the presence of fatty acids, carbohydrates, saponins, alkaloids, and mainly C-glycosidic flavones. Principal components analysis (PCA) allowed discrimination of Passiflora extracts, which the quadranguloside, oleanolic acid-3-sophoroside, α-glucose, β-glucose, and vitexin-2-O"-rhamnoside were relevant in the differentiation of P. alata and P. alata var. BRS Pérola do Cerrado, while the flavones isovitexin and isovitexin-2-O"-xyloside were dominant in the grouping of P. setacea and P. setacea var. BRS Pérola do Cerrado, and finally P. cincinnata and P. cincinnata var. BRS Sertão Forte grouped by the influence of the fatty acids, sucrose, flavones (isoorientin and vitexin-2-O"-xyloside), and trigonelline. The varieties of P. setacea, and P. cincinnata are chemically equivalent to the original Passiflora species. However, the PCA analysis showed that the genetic variety of P. alata occupied a different position in the scores plot provoked mainly by the presence of oleanolic acid-3-sophoroside. The ¹H NMR metabolic profile can be efficient for quality control evaluation, and can contribute to the investigation of new alternatives for official Passiflora herbal medicines.

Application of 1H HR-MAS NMR-Based Metabolite Fingerprinting of Marine Microalgae

Natural products from the marine environment as well as microalgae, have been known for the complexity of the metabolites they produce due to their adaptability to different environmental conditions, which has been an inexhaustible source of several bioactive properties, such as antioxidant, anti-tumor, and antimicrobial. This study aims to characterize the main metabolites of three species of microalgae (Nannochloropsis oceanica, Chaetoceros muelleri, and Conticribra weissflogii), which have important applications in the biofuel and nutrition industries, by ¹H High-resolution magic angle spinning nuclear magnetic resonance (¹H HR-MAS NMR), a method which is non-destructive, is highly reproducible, and requires minimal sample preparation. Even though the three species were found in the same ecosystem and a superior production of lipid compounds was observed, important differences were identified in relation to the production of specialized metabolites. These distinct properties favor the use of these compounds as leaders in the development of new bioactive compounds, especially against environmental, human, and animal pathogens (One Health), and demonstrate their potential in the development of alternatives for aquaculture.

Investigating phenotypic relationships in persimmon accessions through integrated proteomic and metabolomic analysis of corresponding fruits

Together with phenological and genomic approaches, gel-based and label-free proteomic as well metabolomic procedures were separately applied to plants to highlight differences between ecotypes, to estimate genetic variability within/between organism populations, or to characterize specific mutants/genetically modified lines at metabolic level. To investigate the possible use of tandem mass tag (TMT)-based quantitative proteomics in the above-mentioned contexts and based on the absence of combined proteo-metabolomic studies on Diospyros kaki cultivars, we here applied integrated proteomic and metabolomic approaches to fruits from Italian persimmon ecotypes with the aim to characterize plant phenotypic diversity at molecular level. We identified 2255 proteins in fruits, assigning 102 differentially represented components between cultivars, including some related to pomological, nutritional and allergenic characteristics. Thirty-three polyphenols were also identified and quantified, which belong to hydroxybenzoic acid, flavanol, hydroxycinnamic acid, flavonol, flavanone and dihydrochalcone sub-classes. Heat-map representation of quantitative proteomic and metabolomic results highlighted compound representation differences in various accessions, whose elaboration through Euclidean distance functions and other linkage methods defined dendrograms establishing phenotypic relationships between cultivars. Principal component analysis of proteomic and metabolomic data provided clear information on phenotypic differences/similarities between persimmon accessions. Coherent cultivar association results were observed between proteomic and metabolomic data, emphasizing the utility of integrating combined omic approaches to identify and validate phenotypic relationships between ecotypes, and to estimate corresponding variability and distance. Accordingly, this study describes an original, combined approach to outline phenotypic signatures in persimmon cultivars, which may be used for a further characterization of other ecotypes of the same species and an improved description of nutritional characteristics of corresponding fruits.

From Diospyros kaki L. (Persimmon) Phytochemical Profile and Health Impact to New Product Perspectives and Waste Valorization

Persimmon (Diospyros kaki L.) fruit's phytochemical profile includes carotenoids, proanthocyanidins, and gallic acid among other phenolic compounds and vitamins. A huge antioxidant potential is present given this richness in antioxidant compounds. These bioactive compounds impact on health benefits. The intersection of nutrition and sustainability, the key idea behind the EAT-Lancet Commission, which could improve human health and decrease the global impact of food-related health conditions such as cancer, heart disease, diabetes, and obesity, bring the discussion regarding persimmon beyond the health effects from its consumption, but also on the valorization of a very perishable food that spoils quickly. A broad option of edible products with better storage stability or solutions that apply persimmon and its byproducts in the reinvention of old products or even creating new products, or with new and better packaging for the preservation of food products with postharvest technologies to preserve and extend the shelf-life of persimmon food products. Facing a global food crisis and the climate emergency, new and better day-to-day solutions are needed right now. Therefore, the use of persimmon waste has also been discussed as a good solution to produce biofuel, eco-friendly alternative reductants for fabric dyes, green plant growth regulator, biodegradable and edible films for vegetable packaging, antimicrobial activity against foodborne methicillin-resistant Staphylococcus aureus found in retail pork, anti-Helicobacter pylori agents from pedicel extracts, and persimmon pectin-based emulsifiers to prevent lipid peroxidation, among other solutions presented in the revised literature. It has become clear that the uses for persimmon go far beyond the kitchen table and the health impact consumption demonstrated over the years. The desired sustainable transition is already in progress, however, mechanistic studies and clinical trials are essential and scaling-up is fundamental to the future.

HR-MAS NMR Applications in Plant Metabolomics

Metabolomics is used to reduce the complexity of plants and to understand the underlying pathways of the plant phenotype. The metabolic profile of plants can be obtained by mass spectrometry or liquid-state NMR. The extraction of metabolites from the sample is necessary for both techniques to obtain the metabolic profile. This extraction step can be eliminated by making use of high-resolution magic angle spinning (HR-MAS) NMR. In this review, an HR-MAS NMR-based workflow is described in more detail, including used pulse sequences in metabolomics. The pre-processing steps of one-dimensional HR-MAS NMR spectra are presented, including spectral alignment, baseline correction, bucketing, normalisation and scaling procedures. We also highlight some of the models which can be used to perform multivariate analysis on the HR-MAS NMR spectra. Finally, applications of HR-MAS NMR in plant metabolomics are described and show that HR-MAS NMR is a powerful tool for plant metabolomics studies.

Fruits of wild and semi-domesticated Diospyros tree species have contrasting phenological, metabolic, and antioxidant activity profiles

BACKGROUND

In contrast to commercial Diospyros species, Mesoamerican fruit-producing species are scarcely known, particularly wild species that might harbor desirable traits suitable for breeding. Thus, metabolomic, chemical, and antioxidant profiles of fruits harvested from cultivated Diospyros digyna and wild Diospyros rekoi trees during consecutive winter seasons were obtained. Fruits were harvested in habitats having marked differences in soil quality, climate, and luminosity.

RESULTS

D. digyna fruits were larger and less acid than D. rekoi fruits, whereas antioxidant activity tended to be higher in D. rekoi fruits. Phenolic, flavonoid, and sugar contents also varied significantly between species. Metabolomic analysis allowed the pre-identification of 519 and 1665 metabolites in negative and positive electrospray ionization (ESI) modes, respectively. Principal component analysis of the positive ESI data explained 51.8% of the variance and indicated clear metabolomic differences between D. rekoi and D. digyna fruits that were confirmed by direct-injection ESI mass spectrometry profiles. Twenty-one discriminating metabolites were detected in fruits of both species; D. digyna fruits differentially accumulated lysophospholipids, whereas discriminating metabolites in D. rekoi fruits were chemically more diverse than those in D. digyna fruits.

CONCLUSION

Domesticated D. digyna fruits have improved physicochemical fruit traits compared with wild D. rekoi fruits, including larger size and lower acidity. The metabolomic and chemical composition of their respective fruits were also significantly different, which in D. rekoi was manifested as a notable season-dependent increase in antioxidant capacity. Therefore, wild D. rekoi can be considered as an important genetic resource for the improvement of commercial Diospyros fruit quality. © 2019 Society of Chemical Industry.

Important issues in plant tissues analyses by HR-MAS NMR

INTRODUCTION

High-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy enables the analysis of the metabolic profile of plant and animal tissues under close to natural conditions, as well as of other heterogeneous natural or synthetic materials. Neither sample pretreatment is required after fragmentation nor powdering of the sample before insertion into the rotor. However, the efficiency of the method depends strongly on the sample preparation, rotor insertion procedure, and analysis conditions.

OBJECTIVE

To identify some of the variables that affect the spectral data and to propose solutions that minimise their impact on the quality of the analyses and results.

METHODS

Dried plant tissues were powdered, weighed, and homogenised in a 50 μL rotor with an optimised volume of deuterated solvent and sample in order to prevent material from escaping during spacer insertion, avoiding variations in magnetic susceptibility. Factors affecting the quality of HR-MAS NMR analysis such as particle size, sample and solvent amounts, solvent polarity, swelling time, rotor manipulation and pulse sequence setting were evaluated.

RESULTS

A strong correlation was observed between the signal area and the particle size of the powdered sample. The spectral profile varied depending on the deuterated solvent used. An incubation period was necessary to achieve adequate swelling of the sample and to ensure good data reproducibility. Proper sealing of the rotor, number of cycles and τ time on cpmgpr1d pulse sequence were found to affect the signal areas.

CONCLUSION

The study highlights the need for standardised sample preparation and instrumental setup protocols in order to achieve high reproducibility and obtain reliable data from HR-MAS NMR analyses.

1H NMR and antioxidant profiles of polar and non-polar extracts of persimmon (Diospyros kaki L.) - Metabolomics study based on cultivars and origins

Persimmon (Diospyros kaki L.) is one of the most important fruits that has been consumed for its medicinal properties due to the presence of some active metabolites, particularly polyphenols and carotenoids. Previously described methods, including HPLC, were limited in the determination of metabolites in different persimmon varieties. The present study shows the evaluation and the differences among persimmon polar and non-polar extracts by ¹H NMR-based metabolomics approach. The hierarchical clustering analysis (HCA) based on score values of principal component analysis (PCA) model was used to analyze the important compounds in investigated fruits. The ¹H NMR spectrum of persimmon chloroform (CDCl₃) extracts showed different types of compounds as compared to polar methanol-water (CD₃OD-D₂O) ones. Persimmons growing in Israel were clustered different from those growing in Korea with the abundance of phenolic compounds (gallic, caffeic and protocathecuic acids), carotenoids (β-cryptoxanthin, lutein, and zeaxanthin), amino acids (alanine), maltose, uridine, and fatty acids (myristic and palmitoleic acids). Glucose, choline and formic acid were more prominent in persimmon growing in Korea. In CD₃OD-D₂O and CDCl₃ persimmon extracts, 43 metabolites were identified. The metabolic differences were shown as well on the results of bioactivities and antioxidant capacities determined by ABTS, FRAP, CUPRAC and DPPH assays. The presented methods can be widely used for quantitation of multiple compounds in many plant and biological samples especially in vegetables and fruits.