Inhibitory actions of Pseuderanthemum palatiferum(Nees) Radlk. leaf ethanolic extract and its phytochemicals against carbohydrate-digesting enzymes

Objective: To investigate the effects of the leaf ethanolic extract of Pseuderanthemum palatiferum(PPE) and its isolated phytochemicals, stigmasterol and sitosterol-3-O-b-Dglucopyranoside, against a-amylase and a-glucosidase enzyme activities both in vitro and in vivo.Methods: A concentration of maltose, which is a product released in a-amylase-catalyzing reaction, was used as an index of in vitro a-amylase activity. Meanwhile, in vitro a-glucosidase enzyme activity was indicated by the amount of liberated p-nitrophenol in a-glucosidase-catalyzing reaction. In vivo a-amylase and a-glucosidase enzyme activities were evaluated in the normal rats by using oral starch tolerance test and oral sucrose tolerance test, respectively.Results: PPE exerted a concentration-dependent inhibitory action against both aamylase and a-glucosidase in vitro with the IC_(50) values of(11.79 ± 8.10) mg/m L and(1.00 ± 0.11) mg/m L, respectively. Stigmasterol and sitosterol-3-O-b-D-glucopyranoside also exerted an in vitro a-amylase inhibition with the IC_(50) values of(59.41 ± 8.22) mg/m L and(111.19 ± 9.02) mg/m L, respectively. However, these phytochemicals did not produce a concentration-dependent inhibition against in vitro a-glucosidase activity. PPE and its isolated phytochemicals significantly decreased the blood glucose levels at t = 30 min in the oral starch tolerance test. From the sucrose tolerance test, only PPE but not its isolated phytochemicals significantly caused a depletion in the blood glucose levels at t = 30 min Conclusions: These results indicate an inhibitory action against carbohydrate-digesting enzymes as the anti-diabetic mechanism of action of PPE. Nonetheless, further clinical study is required to justify its role in the treatment of diabetes.

New In Vitro Studies on the Bioprofile of Genista tenera Antihyperglycemic Extract

The inhibition of a-glucosidase and glucose-6-phosphatase,two enzymes involved in the carbohydrate metabolism,is an important target to control glycaemia on individuals with type 2 diabetes.In this work we report for the first time the inhibition of both enzymes by the antihyperglycemic n-butanol extract from Genista tenera(Fabaceae).This extract decreased a-glucosidase and glucose-6-phosphatase activities to 0.97 and 80.25%,respectively,being more effective than acarbose,and phlorizin,the positive controls,which reduced enzymes activities only to 17.39 and 96.06%.Once inflammation and oxidative stress are related to diabetic impairments,the anti-inflammatory activity of the extract was also evaluated,through its inhibitory activity over COX-1 enzyme(47.5%inhibition).Moreover,after induction of oxidative stress by UV radiation,the viability of irradiated rat liver hepatoma cells exposed to the extract was significantly higher(67.82%)than that promoted by ascorbic acid,the positive control(45.05%).In addition,the stability of the extract under gastrointestinal conditions was evaluated by HPLC–DAD-ESI–MS/MS.Flavonoid diglycosides were identified as the main constituents of the extract,and no alterations in the chemical composition nor in the antioxidant activity were observed after in vitro digestion with artificial gastric and pancreatic juices.

Two novel resin glycosides isolated from Ipomoea cairica with α-glucosidase inhibitory activity

In the present study, two new compounds from Ipomoea cairica were identified and demonstrated to have a-glucosidase inhibitory activity. They were isolated by column chromatography on silica gel and sephadex LH-20 and finally purified by prep-HPLC, with their structures being elucidated by spectroscopic methods, such as 1D- and 2D-NMR and HR-TOF-MS, and chemical methods. Compounds 1 and 2, named cairicoside A and cairicoside B, were evaluated for a-glucosidase inhibitory activity by the MTT method, with the ICs0 values being 25.3 ± 1.6 and 28.5± 3.3 μmol·L-1, respectively.

The antioxidant activity,c-glucosidase and acetylcholinesterase inhibition activity,and chemical composition of Paeonia delavayi petal

Objectives:This study aimed to evaluate the functional activity and phytochemical composition in the flower petals of Paeonia delavayi(P delavay)in different colors.Materials and Methods:P delavayi petal extracts were prepared by maceration in methanol,including purple petal extract(PPE),red petal extract(RPE),and yellow petal extract(YPE),and their antioxidant activity and x-glucosidase and acetylcholinesterase inhibition activities were evaluated.To correlate these measured activities to phytochemicals in the petals,an ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS)-based metabolomics method was applied to profile the compositions in the petals of different colors.Finally,the Kyoto Encyclopedia of Genes and Genomes(KEGG)metabolic pathways database was used to identify the related metabolic pathways that are responsible for the production of these polyphenolic phytochermicals in the petals.Results:The results showed that PPE had the highest total phenolic content,total flavonoid content,and the strongest 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt(ABTS)radical scavenging ability,ferric reducing antioxidant power,and acetylcholin-esterase inhibition ability in all three samples,while YPE showed the strongest 2,2-diphenyl-1-picrylhydrazyl(DPPH)scavenging activity and x-glucosidase inhibition ability.A total of 232 metabolites were detected in the metabolomic analysis,198 of which were flavonoids,chalcones,flavonols,and anthocyanins.Correlation analysis indicated that peonidin-3-O-arabinoside and cyanidin-3-O-arabinoside were the major contribu-tors to the antioxidant activity.Principal component analysis showed a clear separation among these three petals.In addition,a total of 38,98,and 96 differential metabolites were identified in PPE,RPE,and YPE,respectively.Pathway enrichment revealed 6 KEGG pathways that displayed significant enrichment differences,of which the anthocyanin biosynthesis,flavone and flavonol biosynthesis were the most enriched signaling pathways,revealing a potential reason for the differences in met abolic and functional levels among different colors of P delavayi petal.Conclusions:P.delavayi petals in different colors have different metabolite contents and functional activities,of which the anthocyanin,flavone,and flavonol metabolites are critical in its functional activities,suggesting the anthocyanin biosynthesis,flavone and flavonol biosynthesis path-ways are the key pathways responsible for both petal color and bioactive phytochemicals in P delavayi flowers.

Inhibition of α-glucosidase activity by N-deoxynojirimycin analogs in several insect phloem sap feeders

Secondary metabolites and synthetic iminosugars that structurally resemble monosaccharides are potent inhibitors of a-glucosidase activity. The enzyme is core in cleaving sucrose in phloem feeding insects and it also plays a crucial role of reducing osmotic stress via the formation of oligosaccharides. Inhibition of hydrolysis by iminosug- ars should result in nutritional deficiencies and/or disruption of normal osmoregulation. Deoxynojirimycin （DNJ） and 2 N-alkylated analogs [N-butyl DNJ （NB-DNJ） and N-nonyl DNJ （NN-DNJ）] were the major iminosugars used throughout the study. The extensive experiments conducted with a-glucosidase of the whitefly Bemisia tabaci indicated the competitive nature of inhibition and that the hydrophilic DNJ is a potent inhibitor in com- parison to the more hydrophobic NB-DNJ and NN-DNJ compounds. The same inhibitory pattern was observed with the psyllid Cacopsylla bidens a-glucosidase. In contrast to the above pattern, enzymes of the aphids, Myzus persicae and Aphis gossypii were more sen- sitive to the hydrophobic iminosugars as compared to DNJ. In vivo experiments in which adult B. tabaci were fed dietary iminosugars, show that the hydrophilic DNJ was far less toxic than the lipophilic NB-DNJ and NN-DNJ. It is proposed that this pattern is attributed to the better accessibility of the hydrophobic NN-DNJ to the a-glucosidase membrane- bound compartment in the midgut. Based on the inhibitory effects of certain polyhydroxy N-alkylated iminosugars, a-glucosidase of phloem feeding hemipterans could serve as an attractive target site for developing novel pest control agents.