Acarbose is an antidiabetic drug which acts by inhibiting α-amylase and α-glucosidase activities but with deleterious side effects. Gallic acid (GA) is a phenolic acid that is widespread in plant foods. We therefore investigated the influence of GA on α-amylase and α-glucosidase inhibitory properties of acarbose (in vitro). Aqueous solutions of acarbose and GA were prepared to a final concentration of 25μM each. Thereafter, mixtures of the samples (50% acarbose + 50% GA; 75% acarbose+25% GA; and 25% acarbose+75% GA) were prepared. The results revealed that the combination of 50% acarbose and 50% GA showed the highest α-glucosidase inhibitory effect, while 75% acarbose+25% GA showed the highest α-amylase inhibitory effect. Furthermore, all the samples caused the inhibition of Fe2+-induced lipid peroxidation (in vitro) in rat pancreatic tissue homogenate, with the combination of 50% acarbose and 50% GA causing the highest inhibition. All the samples also showed antioxidant properties (reducing property, 2,2'-azino-bis (-3-ethylbenzthiazoline-6-sulphonate [ABTS*] and 1,1-diphenyl-2-picrylhydrazyl [DPPH] free radicals scavenging abilities, and Fe2+ chelating ability). Therefore, combinations of GA with acarbose could be employed as antidiabetic therapy, with a possible reduction of side effects of acarbose; nevertheless, the combination of 50% acarbose and 50% GA seems the best.

Objectives: 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 α-amylase and α-glucosidase activities in vitro. Methods: 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 α-amylase and α-glucosidase activities, Fe²⁺ induced lipid peroxidation, and 1,1-diphenyl-2 picrylhydrazyl (DPPH) radical scavenging properties were determined. Fe²⁺ chelating abilities and Ferric Reducing Antioxidant Power (FRAP) properties were also studied. Results: The predominant phenolics detected by GC-FID were kaempferol, rutin, apigenin, luteolin, caffeic acid and quercetin. The results showed that all the Corchorus species significantly (P < 0.05) inhibited α-amylase and α-glucosidase activities dose-dependently (0–8 μg/ml). C. olitorius had the highest α-amylase inhibitory ability while C. bougoudo demonstrated the maximum α-glucosidase inhibition. However, all the Corchorus species inhibited α-glucosidase better than α-amylase and also exhibited antioxidant properties. Conclusions: 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.

This study examined the modulatory effect of Black nightshade (Solanum nigrum L) and African eggplant (Solanum macrocarpon L) leaves on cognitive function, antioxidant status, and activities of critical enzymes of monoaminergic and cholinergic systems of neurotransmission in scopolamine‐administered rats. Cognitive impairment was induced in albino rats pretreated with dietary inclusions of Black nightshade (BN) and African eggplant (AE) leaves by single administration (i.p.) of scopolamine (2 mg/kg body weight). Prior to termination of the experiment, the rats were subjected to spontaneous alternation (Y‐maze) test to assess their spatial working memory. Thereafter, activities of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase (MAO), arginase, and antioxidant enzymes (catalase, SOD, and GST) of rat brain homogenate were determined. Also, the malondialdehyde (MDA), nitrite, and GSH contents of the homogenate were determined. The results showed that pretreatment with dietary inclusions of AE and BN significantly reversed the impairment in the rats’ spatial working memory induced by scopolamine. Similarly, elevations in activities of AChE, BChE, and MAO induced by scopolamine were significantly reversed in rats pretreated with dietary inclusions of AE and BN. In addition, impaired antioxidant status induced by scopolamine was reversed by pretreatment with dietary inclusions of AE and BN. This study has shown that dietary inclusions of AE and BN could protect against cognitive and neurochemical impairments induced by scopolamine, and hence, these vegetables could be used as a source of functional foods and nutraceuticals for the prevention and management of cognitive impairments associated diseases such as Alzheimer's disease.

Aluminum (Al)-induced toxicity in fruit fly (Drosophila melanogaster) is one of the established models for studying neurotoxicity and neurodegenerative diseases. Alkaloid phytochemicals have been reported to exhibit neuroprotective effects. Therefore, the aim of this study is to determine the effect of alkaloid extracts of Andrographis paniculata and Phyllanthus amarus leaves on Al-induced toxicity in wild type Drosophila melanogaster. The flies were exposed to diets containing 40 mM AlCl₃, and the alkaloid extracts (0.1 and 1 mg/ml). Thereafter, the flies were assessed for learning and memory, as well as locomotor performance 14 days post-treatment. This was followed by homogenizing the flies and the homogenates were assayed for acetylcholinesterase, monoamine oxidase and catalase activities, as well as the malondialdehyde content. The results showed that the alkaloid extracts of both leaves could ameliorate the aluminum-induced behavioral and biochemical impairments in the flies. The HPLC analysis of the alkaloid contents revealed that there is an abundance of Amaryllidaceae alkaloids, caffeine and carpaine. Thus, alkaloid extracts from these leaves could serve as promising therapeutic candidates for the management of neurodegenerative disease.