Lingrong Wen

Identification of a novel phenolic compound in litchi (Litchi chinensis Sonn.) pericarp and bioactivity evaluation

Litchi (Litchi chinensis Sonn.) is a delicious fruit widely accepted by consumers all over the world. In this work, phytochemical investigation of litchi pericarp methanol extracts led to the isolation of a novel phenolic, 2-(2-hydroxyl-5-(methoxycarbonyl) phenoxy) benzoic acid, together with kaempferol, isolariciresinol, stigmasterol, butylated hydroxytoluene, 3,4-dihydroxyl benzoate, methyl shikimate and ethyl shikimate. Most were found in litchi pericarp for the first time. Their structures were mainly elucidated by NMR and MS evidences. Antioxidant activities of the eight compounds were determined by a DPPH radical scavenging assay and the results showed that 2-(2-hydroxy-5-(methoxycarbonyl) phenoxy)benzoic acid, kaempferol, isolariciresinol, butylated hydroxytoluene and 3,4-dihydroxy benzoate exhibited good antioxidant activities. An interesting finding was that butylated hydroxytoluene was detected as a natural antioxidant in this work, which was usually taken as a synthesized antioxidant. Furthermore, the novel compound exhibited no inhibitory effects against tyrosinase and α-glucosidase activities.

Structural Identification of (1→6)-α-d-Glucan, a Key Responsible for the Health Benefits of Longan, and Evaluation of Anticancer Activity

Longan is a delicious subtropical fruit with great health-beneficial effects. It has been utilized for disease prevention and health care since ancient age. To explore the chemicals responsible for the health benefits, water-soluble polysaccharides were extracted from longan flesh in this work. A pure polysaccharide (LPS1) was obtained through column purification. Analysis by gas chromatography showed LPS1 was a homopolysaccharide of glucose with glycosidic linkage of →6)-d-Glc-(1→. Nuclear magnetic resonance (NMR) spectra indicated that the configuration of anomeric carbon in glucose residual was α-form. The polysaccharide structure was further confirmed to be (1→6)-α-d-glucan by chemcial shift of C6. The molecular weight of LPS1 was calculated to be 108 kDa, which had 661 glucose residuals. Anticancer assay showed that LPS1 had anticancer activity against the growth of HepG2 cells to a certain extent. However, it did not show any cytotoxicity against MCF-7 breast cancer cells.

Comparative evaluation of rosmarinic acid, methyl rosmarinate and pedalitin isolated from Rabdosia serra (MAXIM.) HARA as inhibitors of tyrosinase and α-glucosidase.

Rabdosia serra has been used in traditional Chinese medicine for centuries. In order to illustrate the pharmaceutical activity of R. serra as hypoglycaemic and skin-whitening agents, rosmarinic acid (confirmed as the major compound in R. serra), methyl rosmarinate and pedalitin isolated from R. serra were evaluated for their inhibitory effects and mechanisms on tyrosinase and α-glucosidase. The inhibitory effects on both tyrosinase and α-glucosidase were in decreasing order, pedalitin>methyl rosmarinate>rosmarinic acid. The IC50 values for the tyrosinase and α-glucosidase activity inhibited by pedalitin were 0.28 and 0.29mM, respectively. Both rosmarinic acid and methyl rosmarinate were considered as noncompetitive inhibitors of tyrosinase, while pedalitin was suggested to be a mixed-type inhibitor of tyrosinase. In the assay of α-glucosidase inhibition, rosmarinic acid was found to be a competitive inhibitor, whereas both methyl rosmarinate and pedalitin were considered as mixed-type inhibitors.

Phenolic contents and cellular antioxidant activity of Chinese hawthorn “Crataegus pinnatifida”

It is evident from various epidemiological studies that consumption of fruits and vegetables is essential to maintain health and in the disease prevention. Present study was designed to examine phenolic contents and antioxidant properties of three varieties of Crataegus pinnatifida (Chinese hawthorn). Shanlihong variety exhibited elevated levels of total phenolics and flavonoid contents, including free and bond phenolics. Procyanidin B2 was most abundant phenolic compound in all samples, followed by epicatechin, chlorogenic acid, hyperoside, and isoquercitrin. The free ORAC values, and free hydro-PSC values were 398.3-555.8 μmol TE/g DW, and 299.1-370.9 μmol VCE/g DW, respectively. Moreover, the free cellular antioxidant activity (CAA) values were 678-1200 μmol of QE/100 g DW in the no PBS wash protocol, and 345.9-532.9 μmol of QE/100 g DW in the PBS wash protocol. C. pinnatifida fruit could be valuable to promote consumer health.

Production of quercetin, kaempferol and their glycosidic derivatives from the aqueous-organic extracted residue of litchi pericarp with Aspergillus awamori

Our previous work exhibited Aspergillus awamori fermentation of the litchi pericarp increased significantly antioxidant activity and DNA protection effect. In this present study, the litchi pericarp and its aqueous-organic extracted residues were fermented by A. awamori in order to elucidate the enhanced beneficial effects. The study identified that rutin which present in litchi pericarp could be deglycosylated to form quercetin and quercetin-3-glucoside after the fermentation. Application the standard compounds (rutin, quercetin 3-glucoside, quercetin, kaempferol-3-glucoside and kaempferol) further revealed the effective biotransformation by A. awamori fermentation. It was hypothesised that rutin was initially dehydroxylated to form kaempferol-3-rutinoside and then deglycosylated to form kaempferol-3-glucoside and kaempferol. To our best knowledge, it is the first report on dehydroxylated effect of polyphenols caused by A. awamori fermentation. Thus, A. awamori fermentation can provide an effective way to produce health benefiting value-added products from litchi pericarp in food industry.

Structural characteristics and antioxidant activities of polysaccharides from longan seed

Ultrasound-assisted extraction was employed to extract polysaccharides from longan seed (LSP), with aids of a Box-Behnken statistical design to investigate the effects of ultrasonic power, time and liquid/solid ratio on the extraction recovery of the LSP. The structural analysis indicated that arabinose, galactose, glucose and mannose were major components of LSP, with →6)-Gal-(→1, Glc-(→1 and →6)-Glc-(1→ glycosidic linkages. In an in vitro antioxidant activity of the 1,1-diphenyl-2-picryldydrazyl radical-scavenging assay, LSP exhibited a dose-dependent property within the concentration range tested.

Structural identification of isomallotusinin and other phenolics in Phyllanthus emblica L. fruit hull

The air-dried fruit hull of Phyllanthus emblica L. was extracted with 95% ethanol, and then the extract was partitioned by diethyl ether and ethyl acetate (EA). The EA fraction was then subjected to separation and purification using silica gel and Sephadex LH-20 column chromatography repeatedly to obtain five hydrolysable tannins. They were identified as mucic acid 1,4-lactone 3-o-gallate (C1), isocorilagin (C2), chebulanin (C3), chebulagic acid (C4) and isomallotusinin (C5) using mass spectrometry and nuclear magnetic resonance (NMR) spectrometry. Isomallotusinin and chebulanin were identified from emblica dried fruit hull for the first time, and isomallotusinin was the first time identified from Phyllanthus. Furthermore, the antioxidant abilities of these hydrolysable tannins were investigated using DPPH and ABTS+ radical scavenging systems. All hydrolysable tannins showed strong DPPH and ABTS+ radical scavenging activities. Isomallotusinin and chebulagic acid exhibited the highest antioxidant activity compared to other purified compounds tested.

Structure, bioactivity, and synthesis of methylated flavonoids

Methylated flavonoids are an important type of natural flavonoid derivative with potentially multiple health benefits; among other things, they have improved bioavailability compared with flavonoid precursors. Flavonoids have been documented to have broad bioactivities, such as anticancer, immunomodulation, and antioxidant activities, that can be elevated, to a certain extent, by methylation. Understanding the structure, bioactivity, and bioavailability of methylated flavonoids, therefore, is an interesting topic with broad potential applications. Though methylated flavonoids are widely present in plants, their levels are usually low. Because developing efficient techniques to produce these chemicals would likely be beneficial, we provide an overview of their chemical and biological synthesis.

Identification of a flavonoid C-glycoside as potent antioxidant

Abstract Flavonoids have been documented to have good antioxidant activities in vitro. However, reports on the cellular antioxidant activities of flavonoid C‐glycosides are very limited. In this work, an apigenin C‐glycoside was purified from Artocarpus heterophyllus by column chromatography and was identified to be 2″‐O‐&bgr;‐D‐xylosylvitexin by nuclear magnetic resonance spectroscopy. The cellular antioxidant activity and anticancer activity of 2″‐O‐&bgr;‐D‐xylosylvitexin were evaluated for the first time. The quantitative structure‐activity relationship was analysed by molecular modeling. Apigenin presented an unexpected cellular antioxidation behaviour. It had an antioxidant activity at low concentration and a prooxidant activity at high concentration, whereas 2″‐O‐&bgr;‐D‐xylosylvitexin showed a dose‐dependent cellular antioxidant activity. It indicated that C‐glycosidation improved the cellular antioxidation performance of apigenin and eliminated the prooxidant effect. The ortho‐dihydroxyl at C‐3′/C‐4′ and C‐3 hydroxyl in the flavonoid skeleton play important roles in the antioxidation behaviour. The cell proliferation assay revealed a low cytotoxicity of 2″‐O‐&bgr;‐D‐xylosylvitexin. Graphical abstract Figure. No caption available. HighlightsThe bioactivity of 2″‐O‐&bgr;‐D‐xylosylvitexin was investigated.Its quantitative structure‐activity relationship was analysed.It had a good cellular antioxidant activity.C‐glycosidation improved the antioxidation performance.C‐glycosidation eliminated the prooxidant effect.

Advantages of the polysaccharides from Gracilaria lemaneiformis over metformin in antidiabetic effects on streptozotocin-induced diabetic mice

In the present study, polysaccharides from Gracilaria lemaneiformis (GLP) were obtained by citric acid extraction, and had a low molecular weight (21.2 kDa) with a high amount of galactose. GLP showed effective inhibitory effects on α-amylase activity. After a six-week animal trial, GLP was found to combat streptozotocin (STZ)-induced diabetes and associated with oxidative stress, via its regulation of glucose and lipid metabolism, repair of pancreatic β-cells, protection of liver and kidney function, promotion of the activities of endogenous antioxidant enzymes, and suppression of lipid peroxidation. A dose-dependent manner was found in these examinations except for the glucokinase level, superoxide dismutase activity, and malondialdehyde content. GLP treatments were also more effective at regulating the insulin level, lipidemic parameters and blood urea nitrogen level than metformin treatment. Thus, GLP is more advantageous than metformin not only in the naturalness of GLP but also in the action of combating STZ-induced diabetes. Accordingly, GLP may be utilized as a potential functional food supplement for diabetes prevention in the future.