In vitro antioxidant activities of African birch [Anogeissus leiocarpus] leaf and its effect on the alpha-amylase and alpha-glucosidase inhibitory properties of acarbose

Objective: This study sought to determine the antioxidant activities of African birch leaf, to assess its interaction with key enzymes relevant to type 2 diabetes [aamylase and alpha-glucosidase] and to evaluate its effect on acarbose in vitro

Methods: One milligram per milliliter of aqueous extract of African birch and acarbose were separately prepared. At the same time, both the African extract and acarbose solution [50:50 v/v] were thoroughly mixed until homogeneity was attained. The phenolic phytoconstituents and antioxidant properties of African birch leaf were subsequently determined. Finally, the effects of African birch extract, acarbose solution and a mixture of acarbose and African birch extract on alpha-amylase and alpha-glucosidase activities were assessed in vitro

Results: The results showed that African birch extract demonstrated a remarkable antioxidant effect, as exemplified by its radical scavenging abilities, Fe2þ chelating ability and prevention of lipid peroxidation. Acarbose had significantly [p < 0.05] higher alpha-amylase [IC[50] = 11.77 mg/ml] and alpha-glucosidase [IC[50] = 9.05 mg/ml] activities compared to African birch extract [alpha-amylase [IC[50] = 242.17 mg/ml]; aglucosidase [IC[50] = 196.35 mg/ml]]. However, the combination of acarbose and African birch extract showed an additive effect on alpha-amylase inhibition, while a resultant synergistic action was observed against alpha-glucosidase inhibition

Antioxidant properties and in vitro alpha-amylase and alpha-glucosidase inhibitory properties of phenolics constituents from different varieties of corchorus spp.

This study investigated the phenolic constituents, antioxidant properties and effect of aqueous extracts from some Corchorus species [C. aestuans, C. bougoudo, C. capsularis, C. olitorius and C. urtifolicus] on alpha-amylase and alpha-glucosidase activities in vitro. Gas Chromatography with Flame Ionization Detector [GC-FID] was used to characterize the phenolic constituents. Aqueous extracts were prepared weight/volume [w/v] and their effects on alpha-amylase and alpha-glucosidase activities, Fe[2+] induced lipid peroxidation, and 1,1-diphenyl[-2] picrylhydrazyl [DPPH] radical scavenging properties were determined. Fe[2+] chelating abilities and Ferric Reducing Antioxidant Power [FRAP] properties were also studied. The predominant phenolics detected by GCFID were kaempferol, rutin, apigenin, luteolin, caffeic acid and quercetin. The results showed that all the Corchorus species significantly [P < 0.05] inhibited alpha-amylase and alpha-glucosidase activities dose-dependently [0-8 micro g/ml]. C. olitorius had the highest alpha-amylase inhibitory ability while C. bougoudo demonstrated the maximum alpha-glucosidase inhibition. However, all the Corchorus species inhibited alpha-glucosidase better than alpha-amylase and also exhibited antioxidant properties. The enzyme inhibitory and antioxidant properties exhibited by the Corchorus species could be attributed to their phenolic constituents and vitamin C content; a possible mechanism by which Corchorus species could elicit therapeutic effects on type 2 diabetes mellitus as obtained in folklore medicine

Blanching alters the phenolic constituents and in vitro antioxidant and anticholinesterases properties of fireweed [Crassocephalum crepidioides]

Objective: This research investigated the effect of blanching on the phenolic distribution and in vitro antioxidant and anticholinesterase properties of the HCl-methanolic extracts from fireweed

Methods: Phenolic-rich extracts were prepared by extracting the powdered blanched and unblanched fireweed leaves with a mixture of absolute 1 M HCl and methanol [1:1 v/v]. The phenolic constituents were analysed using high-performance chromatography coupled to a diode array detector [HPLC-DAD]. Furthermore, the extracts' in vitro antioxidant [1,1-diphenyl-2-picrylhydrazyl [DPPH], 2,2-azinobis[3-ethylbenzo-thiazoline-6-sulfonate [ABTS] radical scavenging and Fe[2+] chelating abilities and inhibition of Fe[2+]-induced lipid peroxidation in isolated rat brain] properties and inhibitory effects against acetylcholinesterase [AChE] and butyrylcholinesterase [BChE] were determined in vitro

Results: The HPLC-DAD analysis detected four phenolic acids [gallic, chlorogenic, caffeic and ellagic acids] and three flavonoids [catechin, rutin and quercetin] that were abundant in the unblanched fireweed extract. The findings further showed that the unblanched fireweed extract had higher antioxidant and AChE and BChE inhibitory properties compared to the blanched fireweed extract

Conclusion: The increased antioxidant and anticholinesterase properties of the unblanched fireweed extract could be linked to its higher concentrations of the phenolic constituents compared to the blanched firewood. Therefore, blanching leads to a decrease in the antioxidant and anticholinesterase properties of fireweed, as evidenced by a reduction/loss in the polyphenolic content from the blanched fireweed

Inhibitory effect of polyphenolic-rich extract from Cola nitida (Kolanut) seed on key enzyme linked to type 2 diabetes and Fe(2+) induced lipid peroxidation in rat pancreas in vitro

<p><b>OBJECTIVE</b>To investigate the inhibitory effect of phenolic-rich extracts from Cola nitida (C. nitida) seeds on key enzymes linked with type-2 diabetes and Fe(2+) induced oxidative stress in rat pancreas.</p><p><b>METHODS</b>The phenolic extract was prepared with 80% acetone (v/v). Subsequently, the antioxidant properties and inhibitory effect of the extract on α - amylase and α - glucosidase as well as on Fe(2+) induced lipid peroxidation in rat pancreas were determined in vitro.</p><p><b>RESULTS</b>The result revealed that C. nitida extract inhibited α-amylase (EC50=0.34 mg/mL) and α-glucosidase (EC50=0.32 mg/mL) activities as well as Fe(2+) induced lipid peroxidation in rat pancreas in a dose dependent manner. In addition, the extract had high DPPH radical scavenging ability (EC50=2.2 mg/mL) and reducing power (8.2 mg AAE/g). Characterization of the main phenolic compounds of the extract using gas chromatography analysis revealed catechin (6.6 mg/100 g), epicatechin (3.6 mg/100 g), apigenin (5.1 mg/100 g) and naringenin (3.6 mg/100 g) were the main compounds in the extract.</p><p><b>CONCLUSIONS</b>This antioxidant and enzyme inhibition could be some of the possible mechanism by which C. nitida is use in folklore for the management/treatment of type-2 diabetes. However, the enzyme inhibitory properties of the extract could be attributed to the presence of catechin, epicatechin, apigenin and naringenin.</p>

Phenolic composition and inhibitory activity of Mangifera indica and Mucuna urens seeds extracts against key enzymes linked to the pathology and complications of type 2 diabetes

Objective: To investigate the phenolic compounds composition and the inhibitory activity of Mangifera indica (M. indica) and Mucuna urens (M. urens) seeds extracts against some key enzymes (α-amylase, α-glucosidase and aldose reductase) implicated in the pathology and complications of type 2 diabetes in vitro. Methods: Reverse phase chromatographic quantification of the major flavonoids and phenolic acids in the seeds extracts was carried out using high performance liquid chromatography coupled with diode array detection. The inhibitory activities of the seeds extracts against α-amylase and α-glucosidase were estimated using soluble starch and ρ{variant}-nitrophenylglucopyranoside as their respective substrates. Inhibition of aldose reductase activity by the extracts was assayed using partially purified lens homogenate of normal male rat as source of enzyme; inhibition of Fe

Attenuation of oxidative stress and hepatic damage by some fermented tropical legume condiment diets in streptozotocin-induced diabetes in rats

OBJECTIVE@#To investigate the modulatory effect of fermented legume condiments diet on oxidative stress in streptozotocin (STZ) induced diabetic rats.@*METHODS@#Adult male Wistar rats were randomly divided into six groups with six animals in each group. Diabetes was induced by intraperitoneal injection of STZ (35 mg/kg b.w.). After being confirmed diabetic, the rats were fed with fermented Bambara groundnut, Locust bean and Soybean diets for 14 days. The plasma was obtained after 14-day treatment and analyzed for hepatic damage marker enzymes (AST, ALT and ALP) and in vivo antioxidant indices.@*RESULTS@#The diabetic untreated rats showed elevated (P<0.05) levels of AST, ALT, ALP and malondialdehyde with reduced activities of glutathione-S-transferase, catalase as well as plasma reduced glutathione, vitamin C and total protein content. However, treatment of diabetic rats with fermented legume condiments diets for 14 days significantly (P<0.05) reversed the above parameters towards normalcy, suggesting their modulation of oxidative stress, which may be due to their high phenolic content and antioxidant capacity.@*CONCLUSIONS@#The attenuation of oxidative stress and protection of hepatic tissue damage by the legume condiment diets in STZ induced diabetic rats compare favourably with that of metformin, a well known oral hypoglycemic drug.

In vitro inhibition activity of polyphenol-rich extracts from Syzygium aromaticum (L.) Merr. & Perry (Clove) buds against carbohydrate hydrolyzing enzymes linked to type 2 diabetes and Fe(2+)-induced lipid peroxidation in rat pancreas

<p><b>OBJECTIVE</b>To investigate and compare the inhibitory properties of free and bound phenolic extracts of clove bud against carbohydrate hydrolyzing enzymes (alpha-amylase & alpha-glucosidase) and Fe(2+)-induced lipid peroxidation in rat pancreas in vitro.</p><p><b>METHODS</b>The free phenolics were extracted with 80% (v/v) acetone, while bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate. Then, the interaction of the extracts with alpha-amylase and alpha-glucosidase was subsequently assessed. Thereafter, the total phenolic contents and antioxidant activities of the extracts were determined.</p><p><b>RESULTS</b>The result revealed that both extracts inhibited alpha-amylase and alpha-glucosidase in a dose-dependent manner. However, the alpha-glucosidase inhibitory activity of the extracts were significantly (P<0.05) higher than their alpha-amylase inhibitory activity. The free phenolics (31.67 mg/g) and flavonoid (17.28 mg/g) contents were significantly (P<0.05) higher than bound phenolic (23.52 mg/g) and flavonoid (13.70 mg/g) contents. Both extracts also exhibited high antioxidant activities as typified by their high reducing power, 1,1 diphenyl-2- picrylhydrazyl (DPPH) and 2, 2-azinobis-3-ethylbenzo-thiazoline-6-sulfonate (ABTS) radical scavenging abilities, as well as inhibition of Fe(2+)-induced lipid peroxidation in rat pancreas in vitro.</p><p><b>CONCLUSIONS</b>This study provides a biochemical rationale by which clove elicits therapeutic effect on type 2 diabetes.</p>