Anti-oxidant,anti-glycant,and inhibitory activity against α-amylase and α-glucosidase of selected spices and culinary herbs

Aqueous and methanol extracts of dry sage, rosemary, basil, parsley, chili, garlic and onion were analyzed to investigate their anti-oxidant and anti-glycant activities and in vitro inhibitory potential against enzymes involved in glycemic regulation. The aqueous extracts of rosemary and sage were the richest in phenolic compounds and showed the highest ability in binding iron and inhibiting DPPH, superoxide radicals and advanced glycation end-product production, lipid peroxidation, and the activity of α-glucosidase and α-amylase. On the other hand, the methanol extracts of both these Labiatae were less efficient than those of garlic, onion, parsley and chili in scavenging hydroxyl radicals. As far as protein glycation is concerned, methanol extracts were more effective in inhibiting the production of Amadori compounds and the aqueous ones in preventing advanced glycation end-product formation. Therefore these spices may be preventive not only against cardiovascular diseases but also type 2 diabetes.     

Evaluation of α-glucosidase, α-amylase and protein glycation inhibitory activities of edible plants

Abstract

The present study was to investigate in vitro α-glucosidase, pancreatic α?amylase and protein glycation inhibitory activities of nine edible plants. The results indicated that total phenolics, flavonoids, and condensed tannins of nine edible plants showed marked variations, ranging from 12.2 to 80.1 mg gallic acid equivalent/g extract, 2.34 to 13.65 mg quercetin equivalent/g extract, and 97.2 to 460.1 mg catechin equivalent/g extract, respectively. Our findings showed that grape seed, Cat's whiskers and Sweetleaf extract were the most effective pancreatic α-amylase, intestinal maltase, and sucrase inhibitor with IC₅₀ values of 0.29 ± 0.01 mg/ml, 0.97 ± 0.10 mg/ml and 0.86 ± 0.01 mg/ml, respectively. All extracts (1 mg/ml) markedly inhibited the glycation of bovine serum albumin in fructose-mediated non-enzyme glycation by 50–30% at week 1. It was found that Pennywort maintained the high percentage inhibition among those of the extracts during the 4 weeks of experiment. These edible plants may be used for controlling blood glucose level and prevention of the development of type 2 diabetes.     

Effect of combination on the antioxidant and inhibitory properties of tropical pepper varieties against α-amylase and α-glucosidase activities in vitro

Pepper used as a spice for food preparations is usually a single type or a combination of several different varieties. This choice is usually based on individual preferences, without consideration of health benefits. Therefore, the present study investigated the health benefits of a combination of 3 pepper varieties commonly consumed in Nigeria. Aqueous extracts (1:100?w/v) of Capsicum annuum var. grossum, C. annuum var. abbreviatum, and C. annuum var. accuminatum and a combination of the 3 varieties (1:1:1) were assayed for phenolic content (total phenol and flavonoid), antioxidant activities (reducing power and 1,1-diphenyl-2-picrylhydrazyl radical-scavenging abilities), inhibitory effect on Fe2?-induced lipid peroxidation in rat pancreas in vitro, and the ability of the extracts to inhibit key enzymes linked with type 2 diabetes (α-amylase and α-glucosidase). The combination of peppers showed additive effects in their phenolic content and displayed antioxidant properties. However, the inhibition of pancreatic α-amylase activity showed an additive effect, whereas α-glucosidase inhibitory activity was antagonistic with the combination. C. annuum var. accuminatum contributed most to the activities of the combined peppers. Strong inhibitory activities of the peppers against key enzymes linked to type 2 diabetes and Fe2?-induced lipid peroxidation in rat pancreas in vitro, coupled with their antioxidant properties, suggest that pepper could be used in the prevention and management of type 2 diabetes. The pepper combination showed additive tendencies of these properties.     

Inhibition of α-glucosidase and α-amylase by diaryl derivatives of imidazole-thione and 1,2,4-triazole-thiol

The in vivo and in vitro effects of 4,5-diphenylimidazole-2-thione (1), 4,5-diphenyl-1,2,4-triazole-3-thiol (2) and 5-(2-hydroxyphenyl)-4-phenyl-1,2,4-triazole-3-thiol (3) on α-glucosidase and α-amylase were investigated. The in vivo inhibition has been found to be dose-dependent and to occur at a value less than LD50. The in vitro treatment of the enzymes by 4,5-diphenylimidazole-2-thione exhibited a reversible inhibition of the non-competitive type with Ki value of 3.5 and 6.5×10(-5) M for α-glucosidase and α-amylase, respectively. 4,5-diphenyl-1,2,4-triazole-3-thione showed a reversible inhibition of the competitive and non-competitive types, with Ki value of 10(-5) M magnitude, for α-glucosidase and α-amylase. On the other hand, 5-(o-hydroxyphenyl)-4-phenyl-1,2,4-triazole-3-thione did not display an inhibitory effect towards α-amylase but showed a potent inhibition of the competitive type for hepatic α-glucosidase with 10(-5) M magnitude of Ki value.     

The ingredients in Saengshik,a formulated health food,inhibited the activity of α-amylase and α-glucosidase as anti-diabetic function

BACKGROUND/OBJECTIVES

We investigated total 26 ingredients of Saengshik which will be commercially produced as an anti-diabetic dietary supplement.

SUBJECTS/METHODS

Thirteen vegetables, nine cereals, three legumes and one seed were extracted with aqueous ethanol for 2 h at 60℃, and evaluated for their inhibitory effects against α-amylase and α-glucosidase and for total phenolic and flavonoid contents.

RESULTS

All ingredients inhibited α-amylase activity except cabbage. Strong inhibitory activity of α-amylase was observed in leek, black rice, angelica and barley compared with acarbose as a positive control. Stronger inhibition of α-glucosidase activity was found in small water dropwort, radish leaves, sorghum and cabbage than acarbose. All Saengshik ingredients suppressed α-glucosidase activity in the range of 0.3-60.5%. Most ingredients contained total phenols which were in the range of 1.2-229.4 mg gallic acid equivalent/g dried extract. But, total phenolic contents were not observed in carrot, pumpkin and radish. All ingredients contained flavonoid in the range of 11.6-380.7 mg catechin equivalent/g dried extract.

CONCLUSIONS

Our results demonstrate that Saengshik containing these ingredients would be an effective dietary supplement for diabetes.     

Effects of flavonoids on α-glucosidase activity: potential targets for glucose homeostasis

ObjectiveFlavonoids are naturally occurring compounds widely distributed in plants, which have hypoglycemic potential and have been described as glucosidase inhibitors. This study evaluated the effect of flavonoids on intestinal glucosidase activity after in vivo and in vitro treatment.MethodsFor the in vivo studies animals received quercetin by gavage and for the in vitro assays a segment of the small intestine was used. To obtain the oral glucose tolerance curve fasted normal rats were loaded with glucose plus flavonoids. The glycemia was measured by the glucose oxidase method.ResultsQuercetin reduced the effect of sucrase and maltase in the in vivo and in vitro treatments. It was observed in the in vitro studies that the maximum inhibitory effect of kaempferitrin was around 23% for maltase activity. Also, for the sucrose substrate the specific enzyme activity was significantly decreased. Aglycone, flavonoids, and kaempferol decreased significantly the maltase activity at all concentrations assayed. Finally, rutin reduced maltase-specific activity at all concentrations studied. According to the oral glucose tolerance curve, rutin reduced the serum glucose levels at 15, 30, and 60 min when administered by oral gavage 30 min before glucose overload in rats.ConclusionBased on these results, we can conclude that disaccharidases are targets of flavonoids in the regulation of glucose absorption and consequently glucose homeostasis.     

Hypoglycemic effect of basil (Ocimum basilicum) aqueous extract is mediated through inhibition of α-glucosidase and α-amylase activities: an in vitro study

The present study investigated the in vitro hypoglycemic activity of basil (Ocimum basilicum) aqueous extract. Preliminary phytochemical screening of the extract revealed the presence of reducing sugars, cardiac glycosides, tannins, saponins, glycosides, flavonoids and steroids. The total polyphenols content (TPC), flavonoids content (FC), percentage diphenylpicrylhydrazyl (DPPH( · )) radical inhibition and total antioxidant status (TAS) were estimated. The FC was 41 ± 2.2 rutin/g dry extract, the TPC was 146 ± 5.26 mg catechin/g dry extract and the TAS was 5.12 ± 0.7 mmol/L. The %DPPH( · ) free radical inhibition was 60%, 54%, 49% and 43%, respectively, for different extract concentrations; 20, 18.2, 16.3 and 14.5 mg/ml, respectively. The extract elicited significant dose-dependent pattern against rat intestinal sucrase (RIS; IC(50) = 36.72 mg/ml), rat intestinal maltase (RIM; IC(50) = 21.31 mg/ml) and porcine pancreatic α-amylase (PPA; IC(50) = 42.50 mg/ml) inhibitory activities. The inhibition was greater against maltase compared with sucrase. These effects may be attributed to the high TPC and FC levels. The linear regression analysis revealed strong significant positive correlations between %DPPH( · ) radical inhibition and each of %RIS, %RIM and %PPA inhibiting activity. Also, strong significant positive correlations between %RIS and either %RIM or %PPA inhibition activity were observed. We concluded therefore that basil aqueous extract via antioxidant and possibly α-glucosidase and α-amylase inhibiting activities, offered positive benefits to control diabetes.     

Effect of environmental toxicants on enzyme biosynthesis: A comparison of β-galaclosidase, α-glucosidase and tryptophanase

Except for -galactosidase, little is known about the effect of environmental toxicants on enzyme induction. The information could be potentially useful for the development of low-cost and rapid ecotoxicity assays. The effect of toxicants on thede novo biosynthesis of three inducible enzymes, -galactosidase and tryptophanase inE. coli and -glucosidase inB. subtilis was investigated. Biosynthesis of -glucosidase was the most sensitive to environmental toxicants, particularly pentachlorophenol and sodium dodecyl sulfate. The sensitivity ofB. subtilis to toxicants was further increased when Tween^® 80 was incorporated in the growth medium.     

Synthesis and α1-adrenoceptor antagonist activity of tamsulosin analogues

Tamsulosin (-)-1 is the most utilized α(1)-adrenoceptor antagonist in the benign prostatic hyperplasia therapy owing to its uroselective antagonism and capability in relieving both obstructive and irritative lower urinary tract symptoms. Here we report the synthesis and pharmacological study of the homochiral (-)-1 analogues (-)-2-(-)-5, bearing definite modifications in the 2-substituted phenoxyethylamino group in order to evaluate their influence on the affinity profile for α(1)-adrenoceptor subtypes. The benzyl analogue (-)-3, displaying a preferential antagonist profile for α1A-than α1D-and α1B-adrenoceptors, and a 12-fold higher potency at α1A-adrenoceptors with respect to the α1B subtype, may have improved uroselectivity compared to (-)-1.     

Pomegranate ellagitannins inhibit α-glucosidase activity in vitro and reduce starch digestibility under simulated gastro-intestinal conditions

Abstract

Pomegranate extract was tested for its ability to inhibit α-amylase and α-glucosidase activity. Pomegranate extract strongly inhibited rat intestinal α-glucosidase in vitro whereas it was a weak inhibitor of porcine α-amylase. The inhibitory activity was recovered in an ellagitannins-enriched fraction and punicalagin, punicalin, and ellagic acid were identified as α-glucosidase inhibitors (IC₅₀ of 140.2, 191.4, and 380.9?μmol/L, respectively). Kinetic analysis suggested that the pomegranate extract and ellagitannins inhibited α-glucosidase activity in a mixed mode. The inhibitory activity was demonstrated using an in vitro digestion system, mimicking the physiological gastro-intestinal condition, and potatoes as food rich in starch. Pre-incubation between ellagitannins and α-glucosidase increased the inhibitory activity, suggesting that they acted by binding to α-glucosidase. During digestion punicalin and punicalagin concentration decreased. Despite this loss, the pomegranate extract retained high inhibitory activity. This study suggests that pomegranate ellagitannins may inhibit α-glucosidase activity in vitro possibly affecting in vivo starch digestion.     

Neuroprotective effect of α-mangostin and curcumin against iodoacetate-induced cell death

Abstract

Curcumin is a phenolic yellow curry pigment with anti-inflammatory and antioxidant activities and α-mangostin is a xanthone isolated from mangosteen fruit with antioxidant properties. Iodoacetate (IAA) is an inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase that induces a model of metabolic inhibition in neurons where reactive oxygen species (ROS) production is a significant mechanism. Furthermore, it has been shown that the induction of heme oxygenase-1 (HO-1) protects against IAA-induced neuronal death.

Objectives

To study the effects of α-mangostin and curcumin against the IAA-induced cell death and on HO-1 expression in primary cultures of cerebellar granule neurons (CGNs).

Methods

CGNs were treated with curcumin or α-mangostin before the addition of IAA. Cell viability and ROS production were measured 24 and 4 hours after IAA addition, respectively. HO-1 expression was measured by western blot.

Results

Both α-mangostin and curcumin pretreatment ameliorated the neuronal death induced by IAA in a concentration-dependent way, which was associated with an amelioration of IAA-induced ROS formation. In addition, it was found that α-mangostin and curcumin induced HO-1 expression.

Discussion

Treatment with α-mangostin and curcumin provided a neuroprotective effect against IAA in primary cultures of CGNs, an effect associated with an amelioration of the IAA-induced ROS production. HO-1 induced by these antioxidants may also be involved in the neuroprotective effect. Future work will be required to determine whether α-mangostin may cross the blood–brain barrier and achieve enough bioavailability to elicit a protective response in the brain being an effective nutraceutical compound for preventive therapy of neurodegenerative diseases.     

In vitro investigations of the potential health benefits of Australian-grown faba beans (Vicia faba L.): chemopreventative capacity and inhibitory effects on the angiotensin-converting enzyme, α-glucosidase and lipase

The functional properties, including antioxidant and chemopreventative capacities as well as the inhibitory effects on angiotensin-converting enzyme (ACE), α-glucosidase and pancreatic lipase, of three Australian-grown faba bean genotypes (Nura, Rossa and TF(Ic*As)*483/13) were investigated using an array of in vitro assays. Chromatograms of on-line post column derivatisation assay coupled with HPLC revealed the existence of active phenolics (hump) in the coloured genotypes, which was lacking in the white-coloured breeding line, TF(Ic*As)*483/13. Roasting reduced the phenolic content, and diminished antioxidant activity by 10-40?% as measured by the reagent-based assays (diphenylpicrylhydrazyl, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and oxygen radical absorbance capacity) in all genotypes. Cell culture-based antioxidant activity assay (cellular antioxidant activity) showed an increase of activity in the coloured genotypes after roasting. Faba bean extracts demonstrated cellular protection ability against H2O2-induced DNA damage (assessed using RAW264.7 cells), and inhibited the proliferation of all human cancer cell lines (BL13, AGS, Hep G2 and HT-29) evaluated. However, the effect of faba bean extracts on the non-transformed human cells (CCD-18Co) was negligible. Flow cytometric analyses showed that faba bean extracts successfully induced apoptosis of HL-60 (acute promyelocytic leukaemia) cells. The faba bean extracts also exhibited ACE, α-glucosidase and pancreatic lipase inhibitory activities. Overall, extracts from Nura (buff-coloured) and Rossa (red-coloured) were comparable, while TF(Ic*As)*483/13 (white-coloured) contained the lowest phenolic content and exhibited the least antioxidant and enzyme inhibition activities. These results are important to promote the utilisation of faba beans in human diets for various health benefits.     

Inhibition of aromatase and α-amylase by flavonoids and proanthocyanidins from Sorghum bicolor bran extracts

We compared the ability of simple flavonoids and proanthocyanidins in Sorghum bicolor bran extracts to inhibit enzymes in vitro. In particular, aromatase is a target for breast cancer therapy, and inhibition of α-amylase can reduce the glycemic effect of dietary starches. Proanthocyanidin-rich sumac sorghum bran extract inhibited α-amylase at a lower concentration (50% inhibitory concentration [IC??]=1.4?μg/mL) than did proanthocyanidin-free black sorghum bran extract (IC??=11.4?μg/mL). Sumac sorghum bran extract inhibited aromatase activity more strongly than black sorghum bran extract (IC??=12.1 μg/mL vs. 18.8?μg/mL, respectively). Bovine serum albumin (BSA), which binds proanthocyanidins, reduced inhibition by sumac but not black sorghum bran extract. When separated on Sephadex LH-20, sumac sorghum proanthocyanidins inhibited both enzymes but showed reduced inhibition with BSA. Flavonoids from either cultivar had higher IC?? values than proanthocyanidins, and BSA had little effect on their inhibition. Proanthocyanidins and simple flavonoids in LH-20 fractions both inhibited aromatase with mixed kinetics and affected K(m) and V(max). The results show that potential health benefits of sorghum bran may include actions of monomeric flavanoids as well as proanthocyanidins.     

Alpha-amylase, α-glucosidase and lipase inhibiting activities of polyphenol-rich extracts from six common bean cultivars of Southern Italy,before and after cooking

Common beans (Phaseolus vulgaris) are a good source of nutrients and phenolic compounds with versatile health benefits. Polyphenol-rich extracts of six ecotypes of P. vulgaris were analysed to determine their phenolic profiles and assayed in vitro for inhibitory effects on digestive enzymes relevant to carbohydrates and lipids metabolism. The extracts inhibited enzyme activities in a dose-dependent manner. IC 50 values ranged from 69?±?1.9 to 126?±?3.2?μg/mL and from 107.01?±?4.5 to 184.20?±?5.7?μg/mL, before and after cooking, for α-amylase, from 39.3?±?4.4 to 74.13?±?6.9?μg/mL and from 51?±?7.7 to 122.1?±?5.2?μg/mL for α-glucosidase and from 63.11?±?7.5 to 103.2?±?5.9?μg/mL and from 92.0?±?6.3 to 128.5?±?7.4?μg/mL for lipase. Results suggest encouraging their consumption, being natural sources of enzyme inhibitors important for type-2 diabetes and obesity prevention/control. Well-monitored in vivo studies would help to establish their beneficial effects, making them worthwhile of further consideration as functional foods.     

Characteristic hydrolyzing of megalosaccharide by human salivary α-amylase and small intestinal enzymes,and its bioavailability in healthy subjects

The digestibility of Megalosaccharide® (newly developed carbohydrate comprising α-1,4-glucosaccharide) was investigated in vitro and in vivo. Isomaltosyl-megalosaccharide® (IMS) and nigerosyl-megalosaccharide® (NMS) contain 20% and 50% of the megalosaccharide fraction (degree of polymerization (DP) 10–35), respectively. IMS was hydrolyzed readily by α-amylase to oligosaccharides (DP?≤?7), and a small amount of glucose was produced from oligosaccharides by small intestinal enzymes (SIEs). NMS was partially hydrolyzed by α-amylase to oligosaccharides, and a small amount of glucose produced by SIEs. When IMS and NMS were treated by SIEs after treatment with human saliva α-amylase for a few minutes, IMS and NMS were hydrolyzed readily to glucose. Plasma levels of glucose and insulin upon ingestion of 50?g of IMS or NMS were elevated the same as those for 50?g of glucose, and breath hydrogen was not excreted. These results suggest that IMS and NMS are digestible carbohydrates.     

Effects of administration of α-tocopherol and tocotrienols on serum lipids and liver HMG CoA reductase activity

Male hamsters were fed on semi-synthetic diets containing commercial corn oil (CO), isolated corn oil triglycerides (COTG), COTG supplemented with 30 ppm of α -tocopherol (COTGT L) and COTG supplemented with 81 ppm of α -tocopherol (COTGT H) as the dietary lipid for 45 days. Male albino guinea pigs were fed on commercial chow pellets and treated with different dosages of tocopherol and tocotrienols intra-peritoneally for 6 consecutive days. Serum and liver were taken for analysis. Our results show that stripping corn oil of its unsaponifiable components resulted in COTG which yielded lower serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) and raised high-density lipoprotein cholesterol (HDL-C) and serum triglycerides (TG) levels. These results indicate that the COTG with its fatty acids are responsible for the hypocholesterolemic effect exhibited by corn oil. However, supplementing the COTG diet with α -tocopherol (α -T) at 30 ppm significantly raised the serum TC, LDL-C and TG levels, but did not alter the HDL-C level, indicating that α -T is hypercholesterolemic. Supplementing the COTG diet with α -T at 81 ppm raised the serum TC level but to a lesser extent as compared to that obtained with 30-ppm α -T supplementation. The increased TC, in this case, was reflected mainly by an increased in HDL-C level as the LDL-C level was unchanged. The TG level was also raised but to a lesser extent than that obtained with a lower α -T supplementation. The liver HMG CoA reductase (HMGCR) activity was exhibited (56%) by the COTG as compared to CO. Supplementation of α -T at 30 ppm to the COTG diet resulted in further inhibition (76%) of the liver HMGCR activity. On the contrary, supplementation of α -T at 81 ppm to COTG diet resulted in a highly stimulatory effect (131%) on the liver HMGCR activity. Short-term studies with guinea pigs treated intra-peritoneally with α -T showed that at low dosage (5 mg) the HMGCR activity was inhibited by 46% whereas increasing the dosage of α -T to 20 mg yielded lesser inhibition (18%) as compared to that of the control. Further increase in the dosage of α -T to 50 mg actually resulted in 90% stimulation of the liver HMGCR activity as compared to the control. These results clearly indicate that the effect of α -T on HMGCR activity was dose-dependent. Treatment of the guinea pigs with 10 mg of tocotrienols (T3) resulted in 48% inhibition of the liver HMGCR activity. However, treatment with a mixture of 5 mg of α -T with 10 mg of T3 resulted in lesser inhibition (13%) of the liver HMGCR activity as compared to that obtained with 10 mg of T3. The above results indicate that the α -T is hypercholesterolemic in the hamster and its effect on liver HMGCR is dose-dependent. T3 exhibited inhibitory effect on liver HMGCR and α -T attenuated the inhibitory effect of T3 on liver HMGCR.     

Promoting influence of combinations of amchur, β-carotene-rich vegetables and Allium spices on the bioaccessibility of zinc and iron from food grains

Deficiencies of iron and zinc among the population dependent on plant foods necessitate strategies to maximize their bioavailability. In this context, specific combinations of promoters of iron and zinc bioaccessibility-namely, amchur (0.75?g/10?g), β-carotene-rich vegetables (2.5?g/10?g) and Allium spices (1.5?g/10?g)-were evaluated for a possible additive/synergistic effect on the bioaccessibility of iron and zinc from food grains. The positive influence on the bioaccessibility of iron was additive in the case of combinations of amchur-carrot, amchur-garlic, onion-carrot, and onion-amaranth in a few specific grains. Positive influence on the bioaccessibility of iron was even synergistic for combinations of amchur-onion and amchur-garlic in a few grains. The influence of amchur-garlic and amchur-onion was additive while the combination of amchur-amaranth and amchur-garlic produced a synergistic-promoting influence on zinc bioaccessibility in a few instances. This observation would be useful in evolving dietary strategies to maximize the bioavailability of minerals from grains.