Anticancer activity of bovine α‐lactalbumin treated with microbial transglutaminase

This study investigated the effects of bovine α‐lactalbumin (α‐La) treated with microbial transglutaminase on human cancer cells, cell cultures and growth rate assays. The anticancer activity for 10 mg/mL of bovine α‐lactalbumin (α‐La) was measured as ～90% in a human colorectal cancer cell line HCT 116. For the human bone cancer cell line SJSA‐1, α‐La hydrolysis resulted in higher cytotoxicity compared to untreated tumour cells. The formation of polymers of α‐La was suppressed by the addition of ethylenediaminetetraacetic acid, indicating that polymers of α‐La are promoted by metal ions such as Ca²⁺. The effect of α‐La on the morphology of SJSA‐1 cells was manifested as morphological changes compatible with apoptosis. Bovine milk α‐La with and without microbial transglutaminase is considered a valuable food ingredient and a nutraceutical for human health.     

Proteolysis,protein oxidation and protease activity in dry‐cured Xuanwei ham during the salting stages

Twenty‐four experimental dry‐cured Xuanwei hams were salted using a standard method for 90 days. The proteolysis, protein oxidation and protease activities in biceps femoris (BF) and semimembranoesus (SM) muscles of dry‐cured Xuanwei ham were investigated during the salting phase. At the end of salting, the salt content increased to 35.2 g kg^?1 muscle in BF and 54.2 g kg^?1 muscle in SM. During the salting stage, salt soluble proteins were degraded mainly into water soluble proteins that were further broken down to peptides with molecular weights mostly greater than 1 kDa. Although large amounts of smaller peptides and free amino acids were generated, especially when the hams were aged. The carbonyl contents were increased but lower than 1.57 nmol mg^?1 proteins in muscles during the salting stage. The cathepsin B, dipeptidyl peptidase I (DPP I), alanyl (AAP), arginyl (RAP) and leucyl (LAP) aminopeptidase all remained active while salt content strongly inhibited cathepsin L and DPP IV in the first 90 days. The results suggested that the salting process promoted the hydrolysis of proteins, and increased the muscle protein oxidation at a slower rate.     

Change in α‐tocopherol contents,lipid oxidation and fatty acid profile in eggs enriched with linolenic acid or very long‐chain ω3 polyunsaturated fatty acids after different processing methods

The influences of dietary supplementation with α‐tocopheryl acetate (α‐TA) and of processing (by hard‐boiling and scrambling) of eggs enriched with ω3 fatty acids, either very long‐chain ω3 polyunsaturated fatty acids (VLC ω3 PUFAs) or linolenic acid (LNA), on fatty acid composition, α‐tocopherol content and lipid oxidation (thiobarbituric acid (TBA) values) were studied. Four dietary treatments were formulated from a basal diet containing 40 g kg^?1 linseed oil (LO) or fish oil (FO) combined with either 0 or 100 mg α‐TA kg^?1 of feed. Eggs from LO treatments were enriched with LNA and those from FO treatments were rich in VLC ω3 PUFAs. Neither processing nor dietary supplementation with α‐TA modified greatly the fatty acid profile of eggs. Dietary supplementation with α‐TA increased the α‐tocopherol content of eggs (187.2 versus 407.9 µg g^?1 dry matter). Eggs from FO treatments showed lower α‐tocopherol content than those from LO treatments (273.5 versus 321.6 µg g^?1 dry matter), and processing of eggs enriched with VLC ω3 PUFA reduced the α‐tocopherol content by a significant 16%. Moreover, processing of eggs increased lipid oxidation two‐ to nine‐fold. Oxidation levels of hard‐boiled eggs were 30.4% higher than those of scrambled eggs. TBA values in hard‐boiled and scrambled eggs were significantly reduced when 100 mg α‐TA kg^?1 of feed supplemented the diet only in those eggs enriched with VLC ω3 PUFA (from FO treatments). Copyright © 2003 Society of Chemical Industry     

α‐Lactalbumin solubilisation from a precipitated whey protein concentrates fraction: pH and calcium concentration effects

The selective precipitation of α‐lactalbumin (α‐La) is the basis for one of the possible methods in whey protein fractionation. Calcium concentration, type of acid added and pH play important roles in α‐La precipitation and on the following resolubilisation. Two washing steps are enough for quantitative removal of β‐lactoglobulin entrapped in the precipitate. α‐La losses are minimised during washing steps (5%) when NaCl is used as washing agent. The most important parameter to control during the resolubilisation step is pH, the maximum amount of the initial re‐dissolved α‐La being 76% when the pH is adjusted to 7.5, CaCl2 concentration is 0.2 m and prior precipitation is carried out adding citric acid. Addition of CaCl2 is not necessary to dissolve α‐La because of the fact that there is enough calcium in the precipitate to join all α‐La; however, its presence improves the solubilisation yield (66% vs. 75%).     

Chemical,biological and sensory evaluation of pasta products supplemented with α‐galactoside‐free lupin flours

α‐Galactoside‐free lupin flour has been used to supplement durum wheat semolina flour in order to increase the nutritive value of pasta products. Supplemented pasta products had a shorter cooking time, higher cooking water absorption, cooking loss and protein loss in water than control pasta prepared with only semolina. Sensory evaluation of cooked pastas showed that products supplemented with 80 g kg^?1 of α‐galactoside‐free Lupinus angustifolius var. Emir flour or with 100 g kg^?1 of α‐galactoside‐free Lupinus angustifolius var. Troll flour showed the same acceptability by panellists as the semolina pasta. These levels of supplementation were selected for further studies. The cooked α‐galactoside‐free lupin/semolina pastas showed higher amounts of protein, dietary fibre, calcium, phosphorus, magnesium, zinc and antioxidant capacity than control pasta and a reasonable level of vitamin B₁, vitamin B₂ and vitamin E. Biological assessment of cooked pastas indicated that the true protein digestibility did not change after the fortification of semolina but protein efficiency ratio increased sharply in the pasta supplemented with α‐galactoside‐free lupin flours (2.07 and 1.92 for Emir and Troll lupin varieties, respectively) in comparison with the control pasta (1.11). It is concluded that the α‐galactoside‐free lupin flours are an adequate ingredient to improve the nutritional quality of pasta products without adding flatulent oligosaccharides. Copyright © 2006 Society of Chemical Industry     

α‐Glucosidase and α‐amylase inhibitory activities of phloroglucinal derivatives from edible marine brown alga,Ecklonia cava

BACKGROUND: Diabetes mellitus (DM) is a chronic metabolic disorder characterized by defects in insulin secretion and action, which can lead to damaged blood vessels and nerves. With respect to effective therapeutic approaches to treatment of DM, much effort has being made to investigate potential inhibitors against α‐glucosidase and α‐amylase from natural products. The edible marine brown alga Ecklonia cava has been reported to possess various interesting bioactivities, which are studied here. RESULTS: In this study, five phloroglucinal derivatives were isolated from Ecklonia cava: fucodiphloroethol G ( 1 ), dieckol ( 2 ), 6,6′‐bieckol ( 3 ), 7‐phloroeckol ( 4 ) and phlorofucofuroeckol A ( 5 ); compounds 1, 3 and 4 were obtained from this genus for the first time and with higher yield. The structural elucidation of these derivatives was completely assigned by comprehensive analysis of nuclear magnetic spectral data. The anti‐diabetic activities of these derivatives were also assessed using an enzymatic inhibitory assay against rat intestinal α‐glucosidase and porcine pancreatic α‐amylase. Most of these phlorotannins showed significant inhibitory activities in a dose‐dependent manner, responding to both enzymes, especially compound 2 , with the lowest IC₅₀ values at 10.8 µmol L^?1 (α‐glucosidase) and 124.9 µmol L^?1 (α‐amylase), respectively. Further study of compound 2 revealed a non‐competitive inhibitory activity against α‐glucosidase using Lineweaver‐Burk plots. CONCLUSION: These results suggested that Ecklonia cava can be used for nutritious, nutraceutical and functional foods in diabetes as well as for related symptoms. Copyright © 2009 Society of Chemical Industry     

Beneficial effect of the unsaponifiable matter from rice bran on oxidative stress in vitro compared with α‐tocopherol

Unsaponifiable matter (UM) was prepared from rice bran using n‐hexane extraction followed by removal of its fatty acid methyl ester with supercritical CO₂ under heat‐stable conditions. The UM was made up of 1% of vitamin E isomers, 28% of γ‐oryzanol and 71% of uncharacterized compounds. The aim of this study was to determine the antioxidant activities of the UM, using α‐tocopherol (α‐T) as a positive control, by measuring the Fe³⁺‐reducing antioxidant power (FRAP), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) free‐radical‐scavenging property and lipid peroxidation in rat liver microsomes. In addition, the effects of the UM on the tert‐butyl hydroperoxide (t‐BOOH)‐induced cytotoxicity in cultured rat hepatocytes were also investigated. In FRAP assay and DPPH^? free‐radical‐scavenging assay, the results were expressed g^?1α‐T or g^?1 UM. The amount of UM used in lipid peroxidation assay and cytotoxicity assay was the amount required to have equal amounts of total vitamin E isomers in the sample and the control α‐T. The UM, as well as α‐T, exhibited significant antioxidant activities in FRAP, radical‐scavenging and membrane‐lipid oxidation. The FRAP value for total vitamin E isomers in the UM (TVEIUM) was 9.1 times higher than that for α‐T. In terms of their capacities to perform radical‐scavenging and lipid peroxidation, both TVEIUM and α‐T showed similar antioxidant activities. In experiments using cultured rat hepatocytes, the t‐BOOH‐induced lactate dehydrogenase release was significantly inhibited by the addition of 63.5 and 160 µg ml^?1 of TVEIUM treatments (84 and 89%, respectively), and that of 63.5 and 160 µg ml^?1 of α‐T treatment (88 and 93%, respectively). The antioxidant function against oxidative stress of the UM prepared from rice bran may extend its use to being a potential dietary supplement. Copyright © 2004 Society of Chemical Industry     

Protein interactions with cyanidin‐3‐glucoside and its influence on α‐amylase activity

BACKGROUND: Recent studies indicate that the bioavailability of anthocyanins is extremely low. One of the possible reasons could be their binding to proteins. Therefore, the binding affinity of cyanidin‐3‐glucoside (Cy3glc) to HSA and α‐amylase was investigated by the quenching of protein tryptophan fluorescence. From data obtained, the binding constants and the free Gibbs energy were calculated. The changes in conformation of the proteins tested were studied with circular dichroism and the influence of binding on α‐amylase activity determined. RESULTS: Cy3glc quenched the tryptophan fluorescence and upon ligand binding a change in protein structure was observed related to the corresponding decrease in the α‐amylase activity. The association constants of 25 to 77 × 10³ L mol^?1 were calculated for different proteins, indicating weak interactions of non‐covalent nature. Competitive binding with HSA in the presence of 8‐anilino‐1‐naphthalene sulfonic acid suggest involvement of hydrophobic interactions, in the case of HSA the possible site being subdomain IIA. CONCLUSION: The strongest affinity of Cy3glc for HSA being at pH 7 underlines its potential in transport and distribution of the phenolic compounds in organisms. An influence on salivary amylase activity is possible when drinking berry juices with high anthocyanins content. Copyright © 2008 Society of Chemical Industry     

Phytosterols in banana (Musa spp.) flower inhibit α‐glucosidase and α‐amylase hydrolysations and glycation reaction

Three phytosterols were isolated from Musa spp. flowers for evaluating their capabilities in inhibiting glucosidase and amylase activities and glycation of protein and sugar. The three phytosterols were identified as β‐sitosterol (PS1), 31‐norcyclolaudenone (PS2) and (24R)‐4α, 14α, 4‐trimethyl‐5α‐cholesta‐8, 25(27)‐dien‐3β‐ol (PS3). IC₅₀ values (the concentration of inhibiting 50% of enzyme activity) of PS1, PS2 and PS3 against α‐glucosidase were 283.67, 11.33 and 43.10 μg mL^?1, respectively. For inhibition of α‐amylase, the IC₅₀ values of PS1, PS2 and PS3 were 52.55, 76.25 and 532.02 μg mL^?1, respectively. PS1 was an uncompetitive inhibitor against α‐amylase with K_m at 5.51 μg mL^?1, while PS2 and PS3 exhibited a mixed‐type inhibition with K_m at 52.36 and 2.49 μg mL^?1, respectively. PS1 and PS2 also significantly inhibited the formation of advanced glycation end products (AGEs) in a BSA–fructose model. The results suggest that banana flower could possess the capability in prevention of the diseases associated with abnormal blood sugar and AGEs levels, such as diabetes.     

Glycoalkaloids in potato tubers: the effect of variety and drought stress on the α‐solanine and α‐chaconine contents of potatoes

Six varieties of Solanum tuberosum L potato grown in the Bolivian highlands under drought stress, with and without irrigation, were analysed for their content of glycoalkaloids (GAs). The plant material consisted of three drought‐tolerant varieties from a local breeding programme (PROINPA), Potosina, Chapaquita and Pampeña, and three control cultivated varieties, Malcacho, Sani Imilla and Desiree, either susceptible or relatively tolerant to drought. α‐Solanine and α‐chaconine were quantified in both the peel and flesh of the tubers. A significant increase in GA concentration (α‐solanine + α‐chaconine) was observed under drought stress conditions in most varieties; average concentration increases of 43 and 50% were registered in the improved and control cultivars respectively. In all tested cultivars, however, the GA concentration remained lower than the recommended food safety level (200 mg kg⁻¹ fresh tubers). It ranged from 52.4 to 100 mg kg⁻¹ fresh tubers in the improved cultivars and from 55.6 to 122.3 mg kg⁻¹ fresh tubers in the controls. In the improved and control varieties the α‐solanine content averaged 42.6 and 35.4% of the total potato GAs respectively and was not significantly affected by drought stress, except in Desiree. In all conditions the peel contained the greatest proportion of total GAs. The hybrid variety Pampeña (new drought‐tolerant variety) contained the lowest amounts of GAs, which were lower than those of the control varieties, with and without irrigation. © 2000 Society of Chemical Industry     

Identification of the Critical Amino Acid Residues of Immunoglobulin E and Immunoglobulin G Epitopes in α‐Lactalbumin by Alanine Scanning Analysis

α‐Lactalbumin represents one of the major allergens causing cow milk allergy. Few studies have clearly evaluated immunological relationships between immunoglobulin E (IgE) and immunoglobulin G (IgG)‐binding epitopes of α‐lactalbumin. IgE‐ and IgG‐binding epitopes were immunolabeled with individual sera from cow milk‐allergic patients. Alanine scanning of immunodominant epitopes was used to identify the critical amino acid (aa). Our initial data revealed Val⁸, Phe⁹, Arg¹⁰, Tyr¹⁰³, Leu¹⁰⁵, and His¹⁰⁷ were the critical aa for IgE‐binding epitope. The critical aa of IgG‐binding epitopes were Phe⁹, Leu¹⁵, Pro²⁴, Trp²⁶, and His³². This study will provide necessary information to alter the cDNA to encode a protein capable of activating milk‐specific T cells, but with reduced IgE‐ or IgG‐binding capacity.     

α‐Eleostearic acid is more effectively metabolized into conjugated linoleic acid than punicic acid in mice

BACKGROUND: The objective of this study was to investigate the metabolism of α‐eleostearic acid (α‐ESA, cis9,trans11,trans13‐18:3) and punicic acid (PA, cis9,trans11,cis13‐18:3) and to compare the relative conversion efficiency of these fatty acids into conjugated linoleic acids (CLAs) in mice. RESULTS: Twenty‐four male ICR mice were fed either a control diet or one of two experimental diets supplemented with 10 g kg^?1α‐ESA or PA in the form of triacylglycerols for 6 weeks. The accumulation of PA in all tissues examined was significantly higher than α‐ESA; in both groups it was found that cis9,trans11‐conjugated linoleic acid (cis9,trans11‐18:2) was detected in all tissues examined. The relative conversion rate of α‐ESA into cis9,trans11‐18:2 was significantly higher than that of PA. The highest conversion rate of α‐ESA was found in adipose tissue (91.8%), spleen (91.4%) and kidney (90.7%), and the lowest in the heart (84.6%). The highest conversion rate of PA occurred in the liver (76.2%) and the lowest occurred in the heart (54.5%). CONCLUSION: The present results indicate that both α‐ESA and PA are effectively metabolized into cis9,trans11‐18:2 in mice. These conjugated dietary fatty acids might be useful sources of CLAs in tissues owing to the natural abundance of α‐ESA and PA in some seeds. Copyright © 2009 Society of Chemical Industry     

The effectiveness of butylated hydroxyanisole and α‐tocopherol in inhibiting oxidant‐induced chemical and structural changes of whey protein

The objective of the study was to investigate the role of butylated hydroxyanisole (BHA) and α‐tocopherol in protecting whey protein isolate (WPI) from oxidative modification. The results showed that oxidation increased protein carbonyls and decreased total sulfhydryls, and led to higher dityrosine and surface hydrophobicity (P < 0.05) than nonoxidised WPI. The presence of BHA and α‐tocopherol significantly reduced (P < 0.05) the extent of WPI oxidation, thus limiting the oxidation‐induced protein aggregates and structural changes. Therefore, BHA and α‐tocopherol may be used as potential antioxidants in WPI and WPI‐containing foods.     

Alpha‐Lactalbumin: Its Production Technologies and Bioactive Peptides

ABSTRACT: Alpha‐lactalbumin (α‐La), a globular protein found in all mammalian milk, has been used as an ingredient in infant formulas. The protein can be isolated from milk using chromatography/gel filtration, membrane separation, enzyme hydrolysis, and precipitation/aggregation technologies. α‐La is appreciated as a source of peptides with antitumor and apoptosis, antiulcerative, immune modulating, antimicrobial, antiviral, antihypertensive, opioid, mineral binding, and antioxidative bioactivities, which may be utilized in the production of functional foods. Nanotubes formed by the protein could find applications in foods and pharmaceuticals, and understanding its amyloid fibrils is important in drawing strategies for controlling amyloidal diseases. Bioactive peptides in α‐La are released during the fermentation or ripening of dairy products by starter and nonstarter microorganisms and during digestion by gastric enzymes. Bioactive peptides are also produced by deliberate hydrolysis of α‐La using animal, microbial, or plant proteases. The occurrence, structure, and production technologies of α‐La and its bioactive peptides are reviewed.     

Validation of analytical method for α‐dicarbonyl compounds using gas chromatography–nitrogen phosphorous detector and their levels in alcoholic beverages

This study aimed to establish an analytical method for α‐dicarbonyl compounds (α‐DCs) including glyoxal, methylglyoxal and diacetyl, to determine the content of α‐DCs in 101 various alcoholic beverages using gas chromatography–nitrogen phosphorous detector (GC‐NPD) and to perform exposure assessment. The limit of detection and limit of quantification for α‐DCs were 0.05–0.22 and 0.15–0.70 μg g^?1, respectively. The accuracy and precision were validated in five matrices. The raspberry fruit wine had the highest value at 139.74 μg g^?1 total α‐DCs. The lowest α‐DC concentration among the beverages was detected in rice wine (Makgeolli) at 1.59 μg g^?1. The levels of α‐DCs in various samples were detected as follows: 1.59–56.68 μg g^?1 in rice wine (Makgeolli), 2.73–16.77 μg g^?1 in beer, 8.22–139.74 μg g^?1 in fruit wine and 8.17–91.56 μg g^?1 in rice wine (Cheongju). The estimated daily intake of α‐DCs in the intake‐only group and population group was calculated as 4.22–97.94 μg kg^?1 bw day^?1 and 0.28–7.13 μg kg^?1 bw day^?1, respectively.     

In vitro inhibitory effects of cranberry bean (Phaseolus vulgaris L.) extracts on aldose reductase, α‐glucosidase and α‐amylase

The in vitro inhibitory activities of different seed extracts prepared from cranberry bean mutant SA‐05 and its wild‐type variety Hwachia against aldose reductase, α‐glucosidase and α‐amylase were examined. The results indicated that the polyphenolics‐rich extracts obtained using 800 g kg^?1 methanol and 500 g kg^?1 ethanol demonstrated inhibitory activities against aldose reductase (IC₅₀ of 0.36–0.46 mg mL^?1) and α‐glucosidase (IC₅₀ of 1.32–1.94 mg mL^?1). The 500 g kg^?1 ethanol extracts also showed α‐amylase inhibitory activities (IC₅₀ of 70.11–80.22 μg mL^?1). Subsequent extracts, prepared further with NaCl and H₂O from precipitates of 800 g kg^?1 methanol or 500 g kg^?1 ethanol extracts, exhibited potent α‐amylase inhibitory activities (IC₅₀ of 17.68–38.68 μg mL^?1). A combination of 500 g kg^?1 ethanol extraction plus a subsequent H₂O extraction produced highest polyphenolics and α‐amylase inhibitors. The SA‐05 α‐amylase inhibitor extracts showed greater inhibitory activities than that of Hwachia. Thus, cranberry bean mutant SA‐05 is an advantageous choice for producing anti‐hyperglycaemic compounds.     

α‐Glucosidase Inhibitory Activities of Fatty Acids Purified from the Internal Organ of Sea Cucumber Stichopus japonicas

α‐Glucosidase inhibitory activities of the various solvent fractions (n‐hexane, CHCl₃, EtOAc, BuOH, and water) of sea cucumber internal organ were investigated. 1,3‐Dipalmitolein (1) and cis‐9‐octadecenoic acid (2) with potent α‐glucosidase inhibitory activity were purified from the n‐hexane fraction of sea cucumber internal organ. IC₅₀ values of compounds 1 and 2 were 4.45 and 14.87 μM against Saccharomyces cerevisiae α‐glucosidase. These compounds mildly inhibited rat‐intestinal α‐glucosidase. In addition, both compounds showed a mixed competitive inhibition against S. cerevisiae α‐glucosidase and were very stable at pH 2 up to 60 min. The K_I values of compounds 1 and 2 were 0.48 and 1.24 μM, respectively. Therefore, the internal organ of sea cucumber might be a potential new source of α‐glucosidase inhibitors suitably used for prevention of obesity and diabetes mellitus.     

Effect of caffeic acid on haemoglobin‐mediated lipid and protein oxidation in washed cod mince during ice and frozen storage

BACKGROUND: Little is known about the relation between haemoglobin (Hb)‐mediated lipid and protein oxidation in muscle foods and how these two reactions can be inhibited by naturally occurring antioxidants. This study was aimed at evaluating (1) lipid oxidation and protein oxidation induced by 20 µmol L^?1 Hb during chilled and frozen storage of washed cod mince and (2) the efficiency of 10–1000 ppm (0.063–6.3 mmol L^?1) caffeic acid in preventing these reactions. RESULTS: Addition of 20 µmol L^?1 Hb increased peroxide value (PV), rancid odour, protein carbonylation, protein insolubilisation, redness loss and α‐tocopherol loss in ice‐stored washed cod mince. Since both lipid and protein oxidation developed at the same time, it was not possible to conclude which reaction initiated the other. All studied reactions were efficiently inhibited by ≥ 50 ppm caffeic acid, which could be a result of α‐tocopherol regeneration, general radical scavenging, reduced formation of oxidised Hb forms and/or conformational changes in Hb structure. During frozen storage the only clear effect of Hb was increased PV, and here caffeic acid was less efficient as an antioxidant. CONCLUSION: Hb‐induced lipid and protein oxidation occurred quickly in ice‐stored washed cod mince, and the two reactions could not be separated in time. During frozen storage, Hb caused only limited lipid oxidation. Caffeic acid (≥50 ppm) was an efficient antioxidant during ice storage. Copyright © 2010 Society of Chemical Industry     

Effect of dietary olive leaves (Olea europaea L.) on lipid and protein oxidation of refrigerated stored n‐3‐enriched pork

The objective of this study was to evaluate the effect of dietary olive leaves versus α‐tocopheryl acetate on lipid and protein oxidation of raw and cooked longissimus dorsi muscle from pigs fed diets supplemented with fish oil. Enrichment of pork with the very long chain n‐3 fatty acids increased (P ≤ 0.05) lipid oxidation in both raw and cooked chops during refrigerated storage, and decreased (P ≤ 0.05) the sensory attributes of the cooked chops, but had no effect (P > 0.05) on protein oxidation of both raw and cooked chops. Dietary olive leaves or α‐tocopheryl acetate had no effect (P > 0.05) on the fatty acid composition but decreased (P ≤ 0.05) lipid oxidation while exerting no effect (P > 0.05) on protein oxidation in both raw and cooked chops during refrigerated storage. In addition, dietary olive leaves at 10 g kg^?1 feed and α‐tocopheryl acetate at 200 mg kg^?1 feed exerted (P ≤ 0.05) a beneficial effect on the sensory attributes of cooked n‐3‐enriched chops.     

Inhibitory potential of phenylpropanoid glycosides from Ligustrum purpurascens Kudingcha against α‐glucosidase and α‐amylase in vitro

The leaves of Ligustrum purpurascens are used in a Chinese traditional tea called small‐leaved kudingcha, which is rich in phenylpropanoid glycosides (PPGs) and has many beneficial properties. Two critical exoacting glycoside hydrolase enzymes (glucosidases) involved in carbohydrate digestion are α‐glucosidase and α‐amylase. We investigated the properties of PPGs from L. purpurascens for inhibiting α‐amylase and α‐glucosidase activity in vitro and found IC₅₀ values of 1.02 and 0.73 mg mL^?1, respectively. The patterns of inhibiting both α‐amylase and α‐glucosidase were mixed‐inhibition type. Multispectroscopy and molecular docking studies indicated that the interaction between PPGs and α‐amylase and α‐glucosidase altered the conformation of enzymes, with binding at the site close to the active site of enzymes resulting in changed enzyme activity. Our studies may help in the further health use of small‐leaved kudingcha.