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