Development, characterization and in vitro bile salts binding capacity of selenium nanoparticles stabilized by soybean polypeptides.

The paper presents the positive effect of soybean polypeptides (SP) on the stability and the potential hypolipidemic effect of selenium nanoparticles (SeNPs). After preparing SeNPs, SP with different molecular weight were introduced to stabilize SeNPs. We found that the SP with molecular weight >10 kDa (SP5) had the best stabilizing effect on SeNPs. We inferred that the steric resistance resulting from the long chains of SP5 protected SeNPs from collision-mediated aggregation, and the electrostatic repulsions between SP5 and SeNPs also played a positive role in stabilizing SeNPs. The as-prepared SP5-SeNPs were spherical, amorphous and zero valent. It was proved that SeNPs were bound with SP5 through O- and N- groups in SP5, and the main forces were hydrogen bonds and van der Waals forces. The bile salts binding assay showed that the SP5-SeNPs exhibited a high binding capacity to bile salts, which indicated their potential in hypolipidemic application.

Synthesis, characterization of tuna polypeptide selenium nanoparticle, and its immunomodulatory and antioxidant effects in vivo.

The tuna polypeptide (TP) was used as the reducing agent and the stabilizing agent to synthesize a tuna polypeptide selenium nanoparticle (TP-SeNP) via a green method. An animal experiment was conducted to investigate its immunomodulatory and antioxidant effects in vivo. The results indicated that the TP regulated the accumulation and stabilization of the TP-SeNP. And the conversion of selenium was tested to be 20.44%. The TP-SeNP was about 22 nm in diameter, a mix of spherical and quasi-spherical, and amorphous. The reaction between the TP and Na2SeO3 was entropy-driven spontaneous, and the binding force was mainly hydrophobic. Intake of the TP-SeNP could greatly increase the phagocytic activity of the mononuclear phagocytic system, and the contents of immunological molecules. The antioxidant capacity of the liver was also improved.

Newly generated and increased bound phenolic in lychee pulp during heat-pump drying detected by UPLC-ESI-triple-TOF-MS/MS.

BACKGROUND: During the thermal processing of fruit, it has been observed for phenolic compounds to either degrade, polymerize, or transfer into macromolecules. In this study, the bound and free phenolic compound composition, content, and phenolic-related enzyme activity of lychee pulp were investigated to determine whether the free phenolic had converted to bound phenolic during heat-pump drying (HPD). RESULTS: It was found that after HPD, when compared with the fresh lychee pulp (control), the content of bound phenolics of dried lychee pulp had increased by 62.69%, whereas the content of free phenolics of dried lychee pulp decreased by 22.26%. It was also found that the antioxidant activity of bound phenolics had also increased after drying. With the use of high-performance liquid chromatography-tandem mass spectrometry, it was identified that (+)-gallocatechin, protocatechuic aldehyde, isorhamnetin-3-O-rutoside, 3,4-dihydroxybenzeneacetic acid, and 4-hydroxybenzoic acid were newly generated during HPD, when compared with the control sample. After drying, the contents of gallic acid, catechin, 4-hydroxybenzoic acid, vanillin, syringic acid, and quercetin in bound phenolics had also increased, and polyphenol oxidase and peroxidase still showed enzyme activity, which could be related to the conversion of free phenolics to bound phenolics. CONCLUSION: Overall, during the thermal processing of lychee pulp, the free phenolics weres found to be converted into bound phenolics, new substances were generated, and antioxidant activity was increased. Hence, it was concluded that HPD improved the bound phenolics content of lychee pulp, thus providing theoretical support for the lychee processing industry. © 2021 Society of Chemical Industry.

In vitro simulated digestion and colonic fermentation of lychee pulp phenolics and their impact on metabolic pathways based on fecal metabolomics of mice.

Lychee pulp phenolics (LPP) was subjected to four simulated gastrointestinal digestions and colonic fermentation to investigate the changes in its phenolic composition and bioactivities; the fecal metabolic profiles of LPP-fed mice were also elucidated using UHPLC-ESI-QTOF-MS/MS. After simulated salivary, gastric and intestinal digestion, slight increases in phenolic acids and (+)-catechin occurred relative to undigested LPP, whereas other flavonoids showed an opposite trend. Unlike the above-described separate simulated digestions, successive gastrointestinal digestion significantly enhanced the release of phenolic compounds (p < 0.05), gallic acid (413.79%), ferulic acid (393.69%), (+)-catechin (570.27%) and rutin (247.54%). During colonic fermentation, ten detected phenolics were utilized by gut microbes, among which procyanidin B2 (22.35%) was the most degraded. LPP fermentation accelerated the production of short-chain fatty acids (122.79%). The metabolic pathways altered by LPP including unsaturated fatty acid, biotin, and nicotinamide metabolism may be the potential regulatory mechanisms and associated with the integrity of the gut barrier. These findings indicate that LPP may act as a promising candidate to protect gut health.

Citrus peel flavonoids improve lipid metabolism by inhibiting miR-33 and miR-122 expression in HepG2 cells.

Citrus plants are rich in flavonoids and beneficial for lipid metabolism. However, the mechanism has not been fully elucidated. Both citrus peel flavonoid extracts (CPFE) and a mixture of their primary flavonoid compounds, namely, nobiletin, tangeretin and hesperidin, citrus flavonoid purity mixture (CFPM), were found to have lipid-lowering effects on oleic acid-induced lipid accumulation in HepG2 cells. The carnitine palmitoyltransferase 1α (CPT1α) gene was markedly increased, while the fatty acid synthase (FAS) gene was significantly decreased by both CPFE and CFPM in oleic acid-treated HepG2 cells. Flavonoid compounds from citrus peel suppressed miR-122 and miR-33 expression, which were induced by oleic acid. Changes in miR-122 and miR-33 expression, which subsequently affect the expression of their target mRNAs FAS and CPT1α, are most likely the principal mechanisms leading to decreased lipid accumulation in HepG2 cells. Citrus flavonoids likely regulate lipid metabolism by modulating the expression levels of miR-122 and miR-33.

Lychee pulp phenolics ameliorate hepatic lipid accumulation by reducing miR-33 and miR-122 expression in mice fed a high-fat diet.

Dietary phenolics exhibit hypolipidemic activity by changing lipid metabolism-related microRNA (miRNA) expression. Quercetin 3-O-rutinoside-7-O-α-l-rhamnosidase (quercetin 3-rut-7-rha), rutin and (-)-epicatechin are the main phenolics in lychee (Litchi chinensis Sonn.) pulp. A previous study reported that quercetin 3-rut-7-rha and rutin had hypolipidemic effects. To elucidate these effects and the underlying molecular mechanisms of lychee pulp phenolics (LPPs), the hepatic mRNA and protein expression of lipid metabolism-related genes and their associated miRNAs were measured after ten weeks of treatment with a high-fat diet (HFD) alone or in combination with LPPs. The administration of LPPs significantly reduced the HFD-induced increase in serum total cholesterol and triglyceride levels but increased the HDL-c content. The mRNA and protein expression levels of hepatic adenosine triphosphate-binding cassette transporter A1 (ABCA1) and carnitine palmitoyltransferase 1a (CPT1a) were upregulated, while fatty acid synthase (FAS) mRNA and the corresponding protein expression levels were downregulated by LPPs. Furthermore, the expression levels of miR-33, which directly modulates ABCA1 and CPT1a, and miR-122, which indirectly regulates FAS, were downregulated in mouse hepatocytes. The repression of miR-33 and miR-122 is a possible molecular mechanism of the hypolipidemic effects of LPPs in the liver. Our results suggest a novel hypolipidemic mechanism of LPPs.

Phenolic-rich lychee (Litchi chinensis Sonn.) pulp extracts offer hepatoprotection against restraint stress-induced liver injury in mice by modulating mitochondrial dysfunction.

The pulp from lychee, a tropical to subtropical fruit, contains large quantities of phenolic compounds and exhibits antioxidant activities both in vitro and in vivo. In the present study, we investigated the mechanisms underlying the hepatoprotective effects of lychee pulp phenolics (LPPs) against restraint stress-induced liver injury in mice. After 18 h of restraint stress, increased levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were observed. High levels of thiobarbituric acid reactive substances (TBARS) were also found. Restraint stress causes liver damage, which was protected against by LPP pretreatment at a dosage of 200 mg (kg d)(-1) for 21 consecutive days. This treatment remarkably decreased the serum ALT, AST and TBARS levels, elevated the liver glutathione (GSH) content, and the activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT). Furthermore, respiratory chain complex and Na(+)-K(+)-ATPase activities were enhanced in liver mitochondria, while mitochondrial membrane potential levels and reactive oxygen species (ROS) production decreased. Thus, treatment with LPPs ameliorated restraint stress-induced liver mitochondrial dysfunction. These results suggest that LPPs protect the liver against restraint stress-induced damage by scavenging free radicals and modulating mitochondrial dysfunction. Thus, lychee pulp may be a functional biofactor to mitigate oxidative stress.

Effects of drying methods on physicochemical and immunomodulatory properties of polysaccharide-protein complexes from litchi pulp.

Dried litchi pulp has been used in traditional remedies in China for many years to treat various diseases, and the therapeutic activity has been, at least partly, attributed to the presence of bioactive polysaccharides. Polysaccharide-protein complexes from vacuum freeze-(VF), vacuum microwave-(VM) and heat pump (HP) dried litchi pulp, which were coded as LP-VF, LP-VM and LP-HP, were comparatively studied on the physicochemical and immunomodulatory properties. LP-HP had a predominance of galactose, while glucose was the major sugar component in LP-VF and LP-VM. Compared with LP-VF and LP-VM, LP-HP contained more aspartate and glutamic in binding protein. LP-HP also exhibited a stronger stimulatory effect on splenocyte proliferation at 200 µg/mL and triggered higher NO, TNF-α and IL-6 secretion from RAW264.7 macrophages. Different drying methods caused the difference in physicochemical properties of polysaccharide-protein complexes from dried litchi pulp, which resulted in significantly different immunomodulatory activity. HP drying appears to be the best method for preparing litchi pulp to improve its immunomodulatory properties.

Comparison of physicochemical properties and immunomodulatory activity of polysaccharides from fresh and dried litchi pulp.

Drying is commonly used for preservation and processing of litchi. However, its polysaccharide structure may be altered by the drying process, resulting in biological activity changes. Polysaccharides from fresh and dried litchi pulp (denoted as LPF and LPD, respectively) were isolated, investigated by GC-MS, GPC and UV/IR spectrum analysis and their antitumor and immunomodulatory activities were evaluated in vitro. LPD, the molecular weight of which was lower than that of LPF, contained more protein, uronic acid, arabinose, galactose and xylose. Compared with LPF, LPD exhibited a higher inhibitory effect on the proliferation of HepG2, Hela and A549 cells from 50-750 µg/mL. LPD was also a better stimulator of spleen lymphocyte proliferation, NK cells cytotoxicity and macrophage phagocytosis from 50-400 µg/mL. In summary, drying could change the physicochemical properties and enhance the bioactivity of polysaccharides from litchi pulp. This finding is supported by the fact that dried litchi pulps are used in Traditional Chinese Medicine.

Comparison of the free and bound phenolic profiles and cellular antioxidant activities of litchi pulp extracts from different solvents.

BACKGROUND: The phenolic contents and antioxidant activities of fruits could be underestimated if the bound phenolic compounds are not considered. In the present study, the extraction efficiencies of various solvents were investigated in terms of the total content of the free and bound phenolic compounds, as well as the phenolic profiles and antioxidant activities of the extracts. METHODS: Five different solvent mixtures were used to extract the free phenolic compounds from litchi pulp. Alkaline and acidic hydrolysis methods were compared for the hydrolysis of bound phenolic compounds from litchi pulp residue. The phenolic compositions of the free and bound fractions from the litchi pulp were identified using HPLC-DAD. The antioxidant activities of the litchi pulp extracts were determined by oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) assays. RESULTS: Of the solvents tested, aqueous acetone extracted the largest amount of total free phenolic compounds (210.7 mg GAE/100 g FW) from litchi pulp, followed sequentially by aqueous mixtures of methanol, ethanol and ethyl acetate, and water itself. The acid hydrolysis method released twice as many bound phenolic compounds as the alkaline hydrolysis method. Nine phenolic compounds were detected in the aqueous acetone extract. In contrast, not all of these compounds were found in the other four extracts. The classification and content of the bound phenolic compounds released by the acid hydrolysis method were higher than those achieved by the alkaline hydrolysis. The aqueous acetone extract showing the highest ORAC value (3406.9 µmol TE/100 g FW) for the free phenolic extracts. For the CAA method, however, the aqueous acetone and methanol extracts (56.7 and 55.1 µmol QE/100 g FW) showed the highest levels of activity of the five extracts tested. The ORAC and CAA values of the bound phenolic compounds obtained by acid hydrolysis were 2.6- and 1.9-fold higher than those obtained using the alkaline hydrolysis method. CONCLUSIONS: The free and bound phenolic contents and profiles and antioxidant activities of the extracts were found to be dependent on the extraction solvent used. Litchi exhibited good cellular antioxidant activity and could be a potentially useful natural source of antioxidants.