Eleocharis dulcis corm: phytochemicals, health benefits, processing and food products.

Eleocharis dulcis, an aquatic plant belonging to Cyperaceae family, is indigenous to Asia, and also occurs in tropical Africa and Australia. The edible corm part of E. dulcis is a commonly consumed aquatic vegetable with a planting area of 44.46 × 103 hm2 in China. This work aims to explore the potential of E. dulcis corm for use as a new food source for sufficient nutrients and health benefits by reviewing its nutrients, phytochemicals, functions, processing and food products. Eleocharis dulcis corm contains starches, dietary fibers, non-starch polysaccharides, proteins, amino acids, phenolics, sterols, puchiin, saponins, minerals and vitamins. Among them, phenolics including flavonoids and quinones could be the major bioconstituents that largely contribute to antioxidant, anti-inflammatory, antibacterial, antitumor, hepatoprotective, neuroprotective and hypolipidemic functions. Peel wastes of E. dulcis corm tend to be enriched in phenolics to a much higher extent than the edible pulp. Fresh-cut E. dulcis corm can be consumed as a ready-to-eat food or processed into juice for beverage production, and anti-browning processing is a key to prolonging shelf life. Present food products of E. dulcis corm are centered on various fruit and vegetable beverages, and suffer from single categories and inadequate development. In brief, underutilized E. dulcis corm possesses great potential for use as a new food source for sufficient nutrients and health benefits. © 2021 Society of Chemical Industry.

Structural characterization, neuroprotective and hepatoprotective activities of flavonoids from the bulbs of Heleocharis dulcis.

Chinese water chestnut, the bulb of Heleocharis dulcis, has been widely consumed as fruit or vegetable in China since ancient times. It exhibits health-promoting properties that leads to an extensive study of their active components. Successive chromatography of active fragments of H. dulcis resulted in isolation of five new chalcone-flavonone heterodimers (1-3, 6, 9), four new diverse flavonoids (4, 5, 7, 8), and sixteen known flavonoids derivatives (10-25) were elucidated on the basis of their IR, UV, NMR, MS spectrometry data analysis and references from H. dulcis for the first time. Among these isolates, compounds 4, 7, 9, 12, 13, and 17 showed moderate neuroprotective activity, which increased the cell survival rate from 49.23 ± 3.68% for the model to 67.75 ± 2.75%, 57.83 ± 2.46%, 67.98 ± 2.74%, 58.65 ± 3.43%, 56.14 ± 1.99%, and 56.70 ± 1.38% at 10 µM, respectively. Moreover, compounds 1-3, 15, 16, 18, and 20 were found to moderately improve the HepG2 cell survival rates from 39.53% (APAP, 10 mM) to 45.53-53.44%. The outcome of the study provided crucial information regarding the structural diversity and health benefits of the edible bulbs of H. dulcis.

Preventive Effects of Three Polysaccharides on the Oxidative Stress Induced by Acrylamide in a Saccharomyces cerevisiae Model.

Saccharomyces cerevisiae was used as a model to explore the preventive effect of two marine polysaccharides separately derived from Sepia esculenta ink (SIP) and Laminaria japonica (FL) as well as one terrestrial polysaccharides from Eleocharis tuberosa peel (WCPP) on toxic injury induced by acrylamide (AA). The growth of yeast was evaluated by kinetics indexes including doubling time, lag phase and maximum proliferation density. Meanwhile, intracellular redox state was determined by contents of MDA and GSH, and SOD activity. The results showed that AA inhibited yeast growth and destroyed the antioxidant defense system. Supplement with polysaccharides, the oxidative damage of cells was alleviated. According to the growth recovery of yeast, FL and WCPP had similar degree of capacity against AA associated cytotoxicity, while SIP was 1.5~2 folds as strong as FL and WCPP. SIP and FL significantly reduced production of MDA by AA administration. Moreover, SIP, FL and WCPP increased SOD activity and repressed GSH depletion caused by AA.

Comparison of flavonoids and phenylpropanoids compounds in Chinese water chestnut processed with different methods.

Different processing methods of Chinese water chestnut (CWC; Eleocharis dulcis (Burm.f.) Trin. ex Hensch.) steaming with skin (WPC), cooking with skin (WPS), steaming with peeling (PS), fresh cutting (FF) and cooking with peeling (PC) were compared. Liquid chromatography-mass spectrometry was used to analyze the metabolic profiles of the processed samples. A total of 454 metabolites, including 123 flavonoids and 57 phenylpropanoids, were characterized. The flavonoid and phenylpropanoid profiles were distinguished using PCA. Eighteen flavonoids and six phenylpropanoids were detected and quantitated in the WPC and WPS samples but not in the FF, PC and PS samples. In addition to the O-hexoside of tricin, kaempferol and luteolin were the predominant flavonoids in the WPC and WPS samples, and all three compounds were higher in the WPC and WPS samples than in the FF sample. This study provides new results regarding differences in the metabolite profile of CWC processed with different methods.

Inhibition and interactions of alpha-amylase by daucosterol from the peel of Chinese water chestnut (Eleocharis dulcis).

The alpha-amylase inhibitory effect of daucosterol purified from the peel of Chinese water chestnut (CWC), a common Chinese vegetable, was assessed. The alpha-amylase inhibitory properties were elucidated by enzyme inhibition, fluorescence quenching and molecular docking experiments. It was found that three saponins from CWC peel exhibited potent inhibitory activity on alpha-amylase and daucosterol was found to be the main inhibitory factor against alpha-amylase with a mixed-type mode. Strong fluorescence quenching of alpha-amylase was observed under static fluorescence quenching with hydrophobic interactions with daucosterol. Molecular docking revealed that the conformation of daucosterol in the high-affinity sites I and II of alpha-amylase was optimum, and hydrophobic interactions were produced by daucosterol aglycone, and hydrogen bonding by the ß-D-glucopyranosyl residue. Ingested daucosterol suppressed the elevation of blood glucose levels through inhibition of alpha-amylase in the small intestine in starch-loaded mice. This study provides data supporting the potential benefit of daucosterol from CWC peel in the treatment of diabetes.

Barley ß-glucan concentrate and its acid hydrolysate for the modification of dough making and rheological properties of water chestnut flour.

ß-Glucans are known for their beneficial physiological roles but can be used as potential food hydrocolloid. The present study was performed to assess the potential of barley ß-glucan concentrates (native and partially hydrolyzed) in altering the functional properties of water chestnut flour dough. The ß-glucan concentrate was subjected to partial hydrolysis to prepare a low molecular weight polymer. The WAC, swelling behavior, and pasting properties were significantly modified after the addition of ß-glucan concentrates. The water chestnut dough incorporated with ß-glucan concentrates displayed enhanced viscoelastic and creep characteristics and the efficacy of ß-glucans in providing strength to water chestnut dough depended on its molecular weight. Hydrolyzed ß-glucan concentrates increased the elasticity of dough to the greater magnitude in comparison to its native counterpart.

Development, characterization, and biocompatibility of zinc oxide coupled starch nanocomposites from different botanical sources.

Starch nanoparticles (SNP) were prepared from different botanical sources (wheat, potato, mung bean, water chestnut and mango kernels) and these were further coupled with zinc oxide (ZnO) to form starch nanocomposites. The nanocomposites were characterized for their particle size, morphological properties, energy dispersive X-ray spectroscopy (EDX) and their biocompatibility was analyzed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, using HeLa cells. From the morphological results, it was observed that ZnO forms super molecules with SNP. Further, EDX studies also confirmed the presence of zinc in coupled molecules. The size distribution of ZnO coupled SNP from different botanical sources revealed that the average diameter of nanocomposites ranged between 506 and 1209 nm. ZnO coupled starch nanocomposites were found to be biocompatible with 77-90% cell viability up to 24 h on HeLa cells. Among all botanical sources studied, ZnO coupled mung bean starch nanocomposite showed the highest cell viability (75% up to 50 h) while ZnO coupled potato starch nanocomposite showed the lowest cell viability (65% up to 50 h).

Structural characterization of polysaccharides with potential antioxidant and immunomodulatory activities from Chinese water chestnut peels.

Chinese water chestnut peels are a kind of vegetable processing waste containing many active components such as polysaccharides, the structure of which remains unknown. To elucidate the structure of polysaccharides from Chinese water chestnut peels, two polysaccharides named WVP-1 and WVP-2 were isolated. WVP-1 (3.16 kDa) consisted of mannose (1.75 %), glucose (84.69 %), galactose (6.32 %), and arabinose (7.24 %), while WVP-2 (56.97 kDa) was composed of mannose (3.18 %), rhamnose (1.52 %), glucuronic acid (1.42 %), galacturonic acid (4.83 %), glucose (11.51 %), galactose (36.02 %), and arabinose (41.53 %). Linkage and NMR data indicated that WVP-1 was composed mainly of →4)-α-d-Glcp(1→ and a certain proportion of →3)-ß-d-Glcp-(1→, including linear and branched polysaccharides simultaneously. WVP-2 was a pectin-like polysaccharide with →4)-α-d-GalpA6Me-(1→ units and the branch points of →3,4)-α-l-Arap-(1→, →3,6)-ß-d-Galp-(1→. WVP-2 exhibited stronger potential antioxidant and immunomodulatory activities than WVP-1 in vitro. These results provide a foundation for the further study of polysaccharides from Chinese water chestnut peels.

Necessity of screening water chestnuts for microcystins after cyanobacterial blooms break out.

Water chestnut is one of the most popular vegetables in Asian countries that grows in shallow water. Eighteen water chestnut samples were collected from Lake Tai and six samples were bought at markets in Wuxi, China, in October 2007. Extraction solution of water chestnut was cleaned up with a solid phase extraction column and immunoaffinity chromatography cartridges, then the microcystin (MC) level was detected by indirect competitive enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-mass spectrometry (LC-MS). The results of ELISA showed that there were six samples collected from Lake Tai which contained MCs; the highest level of total MCs was 7.02 ng/g. The results of LC-MS confirmed that MC-LR and MC-RR were present in five samples. The highest level of MC-LR was 1.02 ng/g and that of MC-RR was 4.44 ng/g. Heavy cyanobacterial blooms had occurred, and MCs were detected in water at the points in Lake Tai where MCs occurred in water chestnuts collected in 2007. MCs were not detected in the six samples bought at Wuxi markets. The results suggest that MCs can accumulate in water chestnuts, which is a potential hazard for human health.

Effect of NaCl on physicochemical properties of xanthan gum - Water chestnut starch complexes.

Pasting and functional properties of water chestnut starch (WCS) alone and mixture of WCS and xanthan gum (XG) were determined by addition of NaCl (0.5, 1, and 2%) at fixed water chestnut starch (5%) and xanthan gum (0.3%) concentration. Results indicated that presence of NaCl had a significant impact on functional and pasting properties of both WCS alone and WCS - XG mixture. Pasting temperature of WCS and WCS - XG mixture increased linearly with increasing salt content, whereas a reverse trend was observed in peak viscosity and sets back in case of WCS alone. It was found that addition of NaCl decreased the swelling power of WCS alone, while it increased in case of WCS - XG mixture. The water absorption of WCS - XG improved drastically by the addition of NaCl while a rapid decline in syneresis was observed with WCS - XG mixture. The transparency of both WCS and WCS - XG mixture were found to be increased after the addition of NaCl.

Structural and physicochemical properties of chemically modified Chinese water chestnut [Eleocharis dulcis (Burm. f.) Trin. ex Hensch] starches.

Chinese water chestnut [Eleocharis dulcis (Burm.f.) Trin. ex Hensch] is a starch-rich aquatic plant widely consumed throughout the oriental countries. In this study, different chemically modified Chinese water chestnut starches including acetylated starch (AS), succinylated starch (SS) and carboxymethylated starch (CMS) were prepared. The structural and physicochemical properties of native starch and chemically modified Chinese water chestnut starches were compared for the first time. The degrees of substitution for AS, SS and CMS were 0.087, 0.575 and 0.972, respectively. Results of powder X-ray diffractometry, small-angle X-ray scattering and scanning electron microscopy indicated the crystalline regions and morphology of native starch were destroyed by chemical modification. Notably, carboxymethylation completely destroyed the original morphology of native starch and thus CMS exhibited an amorphous state. Besides, AS and SS showed significantly lower gelatinization properties than native starch. The thermal stability decreased in the order of CMS > AS > native starch > SS, whereas viscoelastic properties decreased in the order of SS > CMS > native starch > AS pastes. Notably, CMS exhibited the highest swelling power, solubility, paste clarity and resistant starch content, implying CMS might have wide applications in food industry.

A systematic comparative study on morphological, crystallinity, pasting, thermal and functional characteristics of starches resources utilized in China.

In this study, starches from diverse botanical sources (arrowroot, cassava, Chinese yam, fern root, kidney beans, lotus seed, taro, and water chestnut) were isolated and examined for morphological, pasting, thermal, and physico-chemical characteristics in order to distinguish their end use potential. Among isolated starches significant differences (p < 0.05) were observed in gelatinization temperatures, morphology, color, pasting, and functional properties. Amylose content of isolated starches varied between 17.12% and 35.62%. X-ray diffraction pattern of isolated starches displayed A-type (arrowroot, cassava, corn, and kidney bean), B-type (potato) and C-type (water chestnut, taro, Chinese yam, fern root, and lotus seed) crystalline pattern. The FT-IR spectra of isolated starches confirmed their carbohydrate nature. Furthermore, the current study affords information for the exploitation of isolated starches from the diverse botanical sources cultivated in China that would be convenient for commercial applications.

Betaines and related ammonium compounds in chestnut (Castanea sativa Mill.).

Chestnut fruits, being poor of simple sugars and consisting mainly of fibers and starch, are among the constituents of Mediterranean diet. While numerous studies report on content of proteins and amino acids in chestnut, no one has appeared so far on betaines, an important class of nitrogen compounds ubiquitous in plants for their protective action in response to abiotic stress. In this study, we analyzed by HPLC-ESI-tandem mass spectrometry, in fruits and flours of varieties of chestnut cultivated in Italy, the composition of betaines and ammonium compounds intermediates of their biosynthesis. Besides the parent amino acids, the compounds quantified were choline, glycerophosphocholine, phosphocholine, glycine betaine, N-methylproline, proline betaine (stachydrine), ß-alanine betaine, 4-guanidinobutyric acid, trigonelline, N,N,N-trimethyllysine. Interestingly, some uncommon derivatives of pipecolic acid, such as N-methylpipecolic acid, 4-hydroxypipecolic acid and 4-hydroxy-N-methylpipecolic acid were identified for the first time in chestnut samples and characterized by MS(n) tandem mass spectrometry.

Effect of cooking methods on nutritional quality and volatile compounds of Chinese chestnut (Castanea mollissima Blume).

This study aimed to evaluate the effects of different cooking methods on the content of important nutrients and volatiles in the fruit of Chinese chestnut. The nutritional compounds, including starch, water-soluble protein, free amino acids, reducing sugar, sucrose, organic acids and total flavonoids, of boiled, roasted and fried chestnuts were significantly (P<0.05) lower than those of fresh chestnuts after cooking, while the amylose, fat, crude protein and total polyphenol content varied slightly (P>0.05). L-Aspartic acid, L-glutamic acid and L-arginine were found to be the main reduced free amino acids in cooked chestnuts. The main aromatic compositions in fresh chestnuts were aldehydes and esters, while ketones, furfural and furan were formed in cooked chestnuts due to the Maillard reaction and degradation of saccharides, amino acids and lipids. Principle component analysis demonstrated that roasting and frying had a similar effect on the nutritional composition of chestnuts, which differed from that of the boiling process.

Enzymatic in situ saccharification of chestnut shell with high ionic liquid-tolerant cellulases from Galactomyces sp. CCZU11-1 in a biocompatible ionic liquid-cellulase media.

In this study, it was the first time to report that the cellulases of Galactomyces sp. CCZU11-1 showed high activity and stability in the culture and reaction media containing IL [Mmim]DMP. Using untreated chestnut shell (CNS) as carbon source in the culture media containing IL [Mmim]DMP (5%, w/v), high activity of FPA (28.6U/mL), xylanase (186.2U/mL), and CMCase (107.3U/mL) were obtained, and 184.9mg/L of total protein was achieved. Furthermore, the changes in the structural features (crystallinity, morphology, and porosity) of the solid residue of CNS utilized with Galactomyces sp. CCZU11-1 were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. After was enzymatically hydrolyzed with the prepared crude enzymes in IL diluted to 20% (w/v), a high yield of reducing sugars, 62.1%, was obtained. Significantly, Galactomyces sp. CCZU11-1 showed high potential for the efficient transformation of lignocellulosic materials to glucose in a single-step process.

Antitumor, Antioxidant, and Nitrite Scavenging Effects of Chinese Water Chestnut (Eleocharis dulcis) Peel Flavonoids.

The preparation, quantification, and characterization of flavonoid compounds from Chinese water chestnut peel (CWCP) flavonoid extract and ethyl acetate fraction (EF), n-butanol fraction, and water fraction were studied. Among these, EF showed the maximum free radical levels (IC50 values of 0.36, 0.40, and 0.37 mg/mL for DPPH•, ABTS•+ , and •OH, respectively), nitrite scavenging effects (IC50 = 1.89 mg/mL), and A549 cell inhibitory activities (IC50 = 776.12 µg/mL) with the highest value of total flavonoid content (TFC, 421.32 mg/g). Moreover, the contents of 8 flavonoids in this fraction were quantified using high-performance liquid chromatography, and fisetin, diosmetin, luteolin, and tectorigenin were the 4 major flavonoids with levels of 31.66, 29.91, 13.69, and 12.41 mg/g, respectively. Luteolin produced a greater inhibition of human lung cancer A549 cells (IC50 = 59.60 µg/mL) than did fisetin, diosmetin, and tectorigenin. Flow cytometry revealed that the cellular mechanisms of luteolin inhibition of A549 cells were achieved via the induction of cell proliferation arrest at G1 phase and apoptosis/necrosis. Our findings suggest that flavonoids are closely associated with antitumor, antioxidant, and nitrite scavenging effects of CWCP.

Preparation and characterisation of the oligosaccharides derived from Chinese water chestnut polysaccharides.

Hydrogen peroxide (H2O2) is a strong oxidant that cleaves glycosidic bonds in polysaccharides. In this study, the oligosaccharides were prepared by removing the starch from Chinese water chestnuts through hydrolysis using α-amylase and then hydrolysing the remaining polysaccharides with H2O2, during which the oligosaccharide yield was monitored. The yield of oligosaccharide was affected by reaction time, temperature, and H2O2 concentration. Extended reaction times, high temperatures, and high H2O2 concentrations decreased oligosaccharide yield. Under optimum conditions (i.e., reaction time of 4h, reaction temperature of 80°C, and 2.5% H2O2 concentration), the maximum oligosaccharide yield was 3.91%. The oligosaccharides derived from Chinese water chestnuts polysaccharides exhibited strong hydroxyl and 2,2-diphenyl-ß-picrylhydrazyl radical scavenging activity when applied at a concentration of 100 µg/mL. The results indicate that the oligosaccharides derived from Chinese water chestnuts polysaccharides possessed good antioxidant properties and can be developed as a new dietary supplement and functional food.

Isolation, purification and identification of etiolation substrate from fresh-cut Chinese water-chestnut (Eleocharis tuberosa).

Fresh cut Chinese water-chestnut is a popular ready-to-eat fresh-cut fruit in China. However, it is prone to etiolation and the chemicals responsible for this process are not known yet. To address this problem, we extracted phytochemicals from etiolated Chinese water-chestnut and separated them using MPLC and column chromatography. Four compounds were obtained and their structures were determined by interpretation of UV, TLC, HPLC and NMR spectral data and by comparison with reported data. We identified these compounds as eriodictyol, naringenin, sucrose and ethyl D-glucoside. Among those, eriodictyol and naringenin were both isolated for the first time in fresh-cut Chinese water-chestnut and are responsible for the yellowing of this fruit cutting.

Thermal stability of texture in Chinese water chestnut may be dependent on 8,8'-diferulic acid (aryltetralyn form).

Ferulic acid (FA) cross-links have been implicated in the thermal stability of texture in Chinese water chestnut (CWC) tissues. The aim of the current study has been to investigate this concept further. CWC tissue strips were measured for their mechanical properties before and after extraction in increasing strengths of alkali. The mechanical properties were related to the associated mode of fracture (cell separation or breakage) at the fracture surfaces and the phenolic composition of the cell walls. CWC tissue softened after prolonged extraction in cold alkali due to an increase in the ease of cell separation. Analysis of wall-bound phenolics demonstrated that most FA moieties, including five of the six dehydrodimers, were released before tissue strength was reduced. Loss of strength was, however, coincident with the loss of 8,8'-diferulic acid, aryltetralin (AT) form. It has been suggested that this dehydrodimer may be particularly concentrated at the edge of the cell faces. These results provide further evidence for the involvement of this dehydrodimer in conferring thermal stability of cell-cell adhesion and hence texture in CWC. However, they do not exclude the other diferulates from involvement in cell adhesion.

Stable isotope food web analysis of a large subtropical lake: alternative explanations for 15N enrichment of pelagic vs. littoral fisheries.

The food webs of littoral, pelagic, and littoral-pelagic ecotone (interface) regions of a large subtropical lake were investigated using stable isotope ratio methods, expanding the focus of a previous fish-only study to include other food web components such as primary producers and invertebrates. In these food webs, delta13C increased approximately 4 per thousand and delta15N increased approximately 10 per thousand from primary producers to fish. The delta15N of fish was approximately 9 per thousand in the littoral zone, approximately 10 per thousand in the ecotone, and approximately 12 per thousand in the pelagic zone. The cross-habitat enrichment in fish 15N corresponded with both an increase in the size of fish and an increase in the d15N of primary consumers (mollusks). Despite larger body size in the pelagic zone, fish in all three habitats appear to occur at the same average trophic level (TL = 4), assuming an enrichment factor of 3.4 per thousand per trophic level, and normalizing to the delta15N of primary consumers.