Chemical Constituents of Pu-erh Tea and Its Inhibition Effect on α-amylase in vitro

[Objective]The aim was to clarify the chemical substance basis of hypoglycemic and lipid-lowering effects of Pu-erh Tea. [Method]Pu-erh Tea was extracted with 95% ethanol,followed by petroleum ether,chloroform,ethyl acetate and n-butanol extraction,after the further purification and through the NKA-9 macroporous resin and many times of Sephadex column chromatography,two compounds were isolated,in the same time,the effect of Uracil and Gallic acid on α-amylase was studied. [Result]The Uracil and Gallic acid were isolated and identified respectively from Pu-erh Tea and the Uracil was firstly isolated from Pu-erh Tea; Gallic acid had strong inhibition on α-amylase. [Conclusion]It could provide some theories on the hypoglycemic and lipid-lowering effects of Pu-erh Tea.

Comparisons of phaseolin type and α-amylase inhibitor in common bean(Phaseolus vulgaris L.)in China

The objective of this study was to characterize the phaseolin type and a-amylase(αAI) level in common bean(Phaseolus vidgaris L.) accessions deposited in the Chinese National Genebank.The 40 accessions sampled were common varieties originating in Asia,North America,South America,Europe,and Africa.No Inca(I-) phaseolin was observed in the accessions.Only four accessions contained Tendergreen(T-) phaseolin and the remaining36 contained Sanilac(S-) phaseolin.aAI proteins extracted from nine accessions showed higher a-amylase inhibitory activity than the control(Phase 2,IC_(50) = 0.65 μg).These common bean accessions have potential use as nutraceutical ingredients.

An in vivo approach to the reported effects of phenolic acids and flavonoids on the pancreaticα-amylase activity

Reduction in the activity of theα-amylases which hydrolyze starch and glycogen has been proposed for diminishing the incidence of obesity and diabetes.Many plant extracts contain inhibitors ofα-amylases andα-glucosidases and several molecules with this activity have been identified.The present work attempts at investigating if several natural compounds(flavonoids and phenolic acids)that have been reported to be inhibitors of those hydrolytic enzymes can also inhibit starch absorption in vivo.The starch tolerance test in mice was used for assaying starch absorption after administration of 100 mg/kg of five flavonoids(epicatechin,catechin,rutin,quercetin,naringenin)and five phenolic acids(gallic,syringic,vanillic,sinapic,ferulic),which are known in vitro inhibitors ofα-amylases.Among the flavonoids,only rutin inhibited starch absorption in mice,even though its effect was only 33%of that one found for the positive control acarbose.Among the five phenolic acids tested only syringic acid produced a clear diminution in starch absorption,which was 47%of that one found with acarbose.On the other hand,other three phenolic acids,namely gallic,sinapic and ferulic acid,caused delay in the absorption of starch,which was characterized by a shift in the time peak of maximal blood glucose concentration,with no modification in the excess of glucose that effectively entered the circulation.Attempts at detecting eventual synergisms by administrating mixtures of flavonoids and phenolic acids were unsuccessful.These results recommend careful translation of in vitro data on the inhibition ofα-amylases andα-glucosidases to the in vivo conditions.

Optimization of High-Protein Glutinous Rice Flour Production Using Response Surface Method

A response surface method was employed to study the effect of α-amylase concentration, hydrolysis temperature and time on the production of high protein glutinous rice flour(HPGRF). The suspension of glutinous rice flour(15%) that contained 6.52% protein was gelatinized and subsequently hydrolyzed by thermostable α-amylase. The hydrolysis yielded 0.144–0.222 g/g HPGRF with 29.4%–45.4% protein content. Hydrolysis time exerted a significant effect, while enzyme concentration and hydrolysis temperature showed insignificant effect on the protein content and production yield of HPGRF. The result of response surface method showed that the optimum condition for the production of HPGRF that contained at least 36% protein was treating gelatinized 15% glutinous rice flour suspension with 0.90 Kilo Novo α-amylase Unit(KNU)/g α-amylase at 80 oC for 99 min. By carrying out the predicted hydrolysis condition, HPGRF with 35.9% protein and 61.8% carbohydrates was resulted. The process yielded 0.172 g/g HPGRF. HPGRF contained higher amount of essential amino acids compared to glutinous rice flour. HPGRF had higher solubility and lower swelling power, and also showed no pasting peak compared with glutinous rice flour.

<i>In Vitro</i>Anti-Diabetic Activities and Phytochemical Analysis of Bioactive Fractions Present in <i>Meriandra dianthera, Aloe camperi</i>and a Polyherb

This paper reports the in vitro anti-diabetic profile of certain medicinal plants traditionally used in Eritrea for the management of type 2 diabetes. The crude methanolic extracts and fractions of Meriandra dianthera, Aloe camperi, a Polyherb and their fractions were investigated. The in vitro screening of the crude extracts has generally elicited a dose dependent α-glucosidase and α-amylase inhibition activities. M. dianthera displayed the highest α-glucosidase inhibitory activity (IC50: 0.074 ± 0.032 mg/mL) at the highest concentration tested (0.800 mg/mL) relative to A. camperi, the Polyherb and Acarbose (IC50: 0.37 ± 0.052, 0.56 ± 0.024 and 0.55 ± 0.029 respectively). The α-glucosidase inhibition activities of A. camperi and M. dianthera, except for the Polyherb and Acarbose, were significantly different (P < 0.05) at various ranges of concentrations (0.025 - 0.800 mg/mL). The percentage α-amylase inhibitions of M. dianthera, A. camperi, the Polyherb and Acarbose, at the highest concentrations (0.800 mg/mL), were 78.3%, 15.9%, 16.4%, and 82.9% respectively. A. camperi and the Polyherb displayed lower α-amylase inhibitory activities (IC50: 1.72 ± 0.06 and 2.57 ± 0.07 mg/mL respectively) compared to Acarbose and M. dianthera (IC50: 0.31 ± 0.01 and 0.43 ± 0.02 mg/mL respectively). For the α-amylase inhibition activity, even at lower concentrations (0.025 mg/mL), there were statistically significant differences (P < 0.01) among the values generated for all the extracts. The in vitro anti-diabetic screening of the fractions, at 0.800 mg/ml, displayed characteristic enzyme inhibition activities. Generally, the non-polar fractions showed higher enzyme inhibitory activities compared to the polar fractions. The most bioactive non-polar fractions, thus, were subjected to GC-MS analysis and presented various essential oils, fatty acid methyl esters (FAMEs) and benzoic acid derivatives in those plants.

Inhibitory effect and mechanism of tannic acid against two starch digestive enzymes

Backgrounds:Tannic acid(TA),as a plant-derived phenolic substance,is involved in regulating the activity of starch digestive enzymes,but its underlying mechanism remains unclear.Methods and Results:In the present study,inhibition rate and inhibition kinetics assays were performed and confrmed that TA had a strong inhibitory effect on bothα-amylase andα-glucosidase with IC50 values of 0.1585 mg/mL and 0.00542 mg/mL,respectively,through a mixed inhibition mode.The secondary structures of both enzymes were confrmed to be modifed by TA through circular dichroism(CD)spectra.Fluorescence quenching analysis revealed that the interaction between TA and two enzymes was a static process of pontaneous complex formation.Finally,molecular docking revealed that non-covalent bonds were the main interaction forces between TA and both enzymes.Conclusions:Thus,TA was a promising candidate for the inhibition of starch-digesting enzymes,and the present research provided insight into postprandial glucose regulation through polyphenols.

Inhibitory potentials of phenolic-rich extracts from Bridelia ferruginea on two key carbohydrate-metabolizing enzymes and Fe^(2＋)-induced pancreatic oxidative stress

Objective： The current study was designed to evaluate the various antioxidant potentials and inhibitory effects of phenolic-rich leaf extracts of Bridelia ferruginea（BF） on the in vitro activities of some key enzymes involved in the metabolism of carbohydrates.Methods： In this study, BF leaf free and bound phenolic-rich extracts were used. We quantified total phenolic and flavonoid contents, and evaluated several antioxidant activities using assays for ferric reducing antioxidant power, total antioxidant activity（phosphomolybdenum reducing ability）, 1,1-diphenyl-2-picrylhydrazyl and thiobarbituric acid reactive species. Also, extracts were tested for their ability to inhibit a-amylase and α-glucosidase activity.Results： The total phenolic and total flavonoid contents in the free phenolic extract of BF were significantly greater than in the bound phenolic extract. Also, all the antioxidant activities considered were significantly greater in the free phenolic extract than in the bound phenolic extract. In the same vein, the free phenolic-rich extract had a significantly higher percentage inhibition against α-glucosidase activity（IC50= 28.5 mg/mL） than the bound phenolic extract（IC50= 340.0 mg/mL）. On the contrary, the free phenolic extract（IC50= 210.0 mg/mL） had significantly lower inhibition against α-amylase than the bound phenolic-rich extract（IC50= 190.0 mg/mL）.Conclusion： The phenolic-rich extracts of BF leaves showed antioxidant potentials and inhibited two key carbohydrate-metabolizing enzymes in vitro.

Nutritional assessment,glycemic indices and anti-diabetic potentials of dough meal generated from optimized blends of matured plantain,soya cake and wheat bran flours

Management of blood glucose levels associated with type 2 diabetes using nutrients derived from food without having a harmful effect on one’s health is gradually gaining research interest.Plantain dough meal blends were developed using optimal mixture design of response surface methodology(RSM).The optimum blends based on the protein and crude fibre contents were as follows:PSW1:mature plantain 70.0%+soya cake 25.0%+wheat bran 5.0%;PSW2:mature plantain 68.0%+soya cake 23.0%+wheat bran 9.00%;PSW3:mature plantain 69.0%+soya cake 24.0%+wheat bran 7.0%,while 100% mature plantain flour(PLNT)and cerolina were used as controls.The nutritional value,amino acid profile,pasting properties,α-amylase,α-glucosidase inhibition potential,in-vitro glycemic index and consumer acceptability were determined using standard methods.Results showed that the inclusion of soya cake and wheat bran significantly increased(P<0.05)protein 14.08 g/100 g and fibre 3.02 g/100 g as observed.Significantly higher(P<0.05)branched chain and aromatic amino acids were observed in the composite dough meal compared to PLNT.The peak viscosity(Pv),trough viscosity(Tv)and final viscosity(Fv)are lower in dough meal blends with increase in incorporation of soya cake and wheat bran.PSW3 showed the highest essential amino acid index,predicted biological value,α-glucosidase,α-amylase inhibition and lowest estimated glycaemic index at(P≤0.05).Hence,the study established that PSW3 showed the best potentials to modulate blood sugar level.