Ayodeji A. Olabiyi

Inhibition of key enzymes linked to type 2 diabetes and sodium nitroprusside-induced lipid peroxidation in rat pancreas by water-extractable phytochemicals from unripe pawpaw fruit (Carica papaya).

Abstract Background: Various parts of unripe pawpaw (Carica papaya Linn) fruit have been reportedly used for the management or treatment of diabetes mellitus in folklore medicine. Therefore, the present study sought to investigate the inhibitory effects of the aqueous extract of different parts of unripe pawpaw fruit on key enzymes linked to type 2 diabetes (α-amylase and α-glucosidase) and sodium nitroprusside (SNP)-induced lipid peroxidation in rat pancreas in vitro. Methods: The aqueous extracts of the unripe pawpaw (C. papaya) fruit parts were prepared (1:20 w/v) and the ability of the extracts to inhibit α-amylase, α-glucosidase and SNP-induced lipid peroxidation in rat pancreas in vitro was investigated. Results: The results revealed that all the extracts inhibited α-amylase (IC50=0.87–1.11 mg/mL), α-glucosidase (IC50=1.76–2.64 mg/mL) and SNP-induced lipid peroxidation (IC50=1.99–2.42 mg/mL) in a dose-dependent manner. However, combination of the flesh, seed and peel in equal amounts had the highest inhibitory effect on α-amylase and α-glucosidase activities. Conclusions: Strong inhibitory activities of the unripe pawpaw fruit against key enzymes linked to type 2 diabetes and SNP-induced lipid peroxidation in rat pancreas could be part of the mechanism by which unripe pawpaw is used in the management/prevention of diabetes mellitus in folk medicine. However, combining the unripe pawpaw fruit parts in equal amounts exhibited synergistic properties on α-amylase and α-glucosidase inhibitory activities.

Neuroprotective effects of quercetin on memory and anxiogenic-like behavior in diabetic rats: Role of ectonucleotidases and acetylcholinesterase activities

The present study investigated the protective effect of quercetin (Querc) on memory, anxiety-like behavior and impairment of ectonucleotidases and acetylcholinesterase (AChE) activities in brain of streptozotocin-induced diabetic rats (STZ-diabetes). The type 1 diabetes mellitus was induced by an intraperitoneal injection of 70mg/kg of streptozotocin (STZ), diluted in 0.1M sodium-citrate buffer (pH 4.5). Querc was dissolved in 25% ethanol and administered by gavage at the doses of 5, 25 and 50mg/kg once a day during 40days. The animals were distributed in eight groups of ten animals as follows: vehicle, Querc 5mg/kg, Querc 25mg/kg, Querc 50mg/kg, diabetes, diabetes plus Querc 5mg/kg, diabetes plus Querc 25mg/kg and diabetes plus Querc 50mg/kg. Querc was able to prevent the impairment of memory and the anxiogenic-like behavior induced by STZ-diabetes. In addition, Querc prevents the decrease in the NTPDase and increase in the adenosine deaminase (ADA) activities in SN from cerebral cortex of STZ-diabetes. STZ-diabetes increased the AChE activity in SN from cerebral cortex and hippocampus. Querc 50mg/kg was more effective to prevent the increase in AChE activity in the brain of STZ-diabetes. Querc also prevented an increase in the malondialdehyde levels in all the brain structures. In conclusion, the present findings showed that Querc could prevent the impairment of the enzymes that regulate the purinergic and cholinergic extracellular signaling and improve the memory and anxiety-like behavior induced by STZ-diabetes.

Inhibitory effect of aqueous extract of different parts of unripe pawpaw (Carica papaya) fruit on Fe2+-induced oxidative stress in rat pancreas in vitro

Abstract Context: Carica papaya L. (Caricaceae) is widespread throughout tropical Africa; it is cultivated for its fruits and it is eaten in various ways. Objective: This study sought to investigate the inhibitory effect of the aqueous extract of different parts of unripe pawpaw fruit on Fe2+-induced lipid peroxidation in rat’s pancreas in vitro. Materials and methods: The aqueous extract of the unripe pawpaw fruit parts; peel (PG), seed (SG), flesh (FG), flesh with peel (FPG) and a combination of equal amount of all parts (CG) were prepared, the total phenolic content and the antioxidant activities of the extracts were then evaluated using various spectrophotometric methods. Result: PG had the highest total phenol content (1.24 mg GAE/g), flavonoid content (0.63 mg QUE/g), reducing power (7.07 mg AAE/g) and Fe2+ chelating ability while the SG had the highest 1,1-diphenyl-2-picrylhydrazyl radical scavenging ability. Furthermore, all the extracts caused a significant decrease (p < 0.05) in the malondialdehyde contents in the pancreas with SG (IC50 = 4.25 mg/mL) having the highest inhibitory effect on Fe2+-induced lipid peroxidation. Discussion and conclusion: This protective effect of the extracts on Fe2+-induced lipid peroxidation in rat pancreas could be attributed to their phenolic compounds and, the possible mechanism may be through their antioxidant activities. However, the effect of combination of different parts of unripe pawpaw fruit in equal amount (w/w) on the inhibition of Fe2-induced lipid peroxidation in rat pancreas exhibited additive properties.

Aqueous extract of Securidaca longipendunculata Oliv. and Olax subscropioidea inhibits key enzymes (acetylcholinesterase and butyrylcholinesterase) linked with Alzheimer’s disease in vitro

Abstract Context: Plants have historically been used to treat neurodegerative diseases which include Alzheimer’s disease. Objective: This study investigated the antioxidant properties and inhibitory effect of aqueous extracts of Securidaca longipendunculata root and Olax subscropioidea leaf on the cholinergic system in rat brain in vitro. Materials and methods: Aqueous extracts (1:20 w/v) of S. longipendunculata root and O. subscropioidea leaf was prepared and the ability of the extract to inhibit the activities of acetylcholinesterase and butyrylcholinesterase was evaluated as well as antioxidants as typified by 2,2-azino-bis-(3-ethylbenthiazoline-6-sulphonic acid (ABTS•) radical scavenging ability and Fe chelation spectophotometrically. Results: ABTS• radical scavenging ability showed that S. longipendunculata (0.075 Mmol TEAC/100 g) had a higher scavenging ability than O. subscropioidea (0.07 Mmol TEAC/100 g). Also, the Fe2+ chelating ability of both extracts revealed that S. longipendunculata (IC50 = 105.57 g/mL) had a significantly (p < 0.05) higher Fe2+ chelating ability than O. subscropioidea (IC50 = 255.84 g/mL). Extracts of S. longipendunculata and O. subscropioidea inhibited acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities. However, S. longipendunculata (IC50 = 108.02 g/mL) has the higher AChE inhibitory activity than O. subscropioidea (IC50 = 110.35 g/mL). Also, both extracts inhibit BChE activity in vitro but S. longipendunculata (IC50 = 82.55 g/mL) had a higher BChE inhibitory activity than O. subscropioidea (IC50 = 108.44 g/mL). Discussion and conclusions: The mechanism by which S. longipendunculata root and O. subscropioidea leaf perform their anti-Alzheimer’s disease activity may be by their inhibition on the key enzymes linked to this disease.

Tetracarpidium conophorum Müll. Arg modulates sexual behaviour and biochemical parameters relevant to sexual function in male Wistar rats

Walnut (Tetracarpidium conophorum Müll. Arg) has been reported to be an essential ingredient in folklore medicine for sexual enhancement with little scientific validation. Hence, this study investigated the effects of walnut supplemented diet on sexual behaviour and biochemical parameters relevant to erection in male Wistar rats. Forty animals used in this study were divided into five groups (n = 8); Group 1 - normal control rats fed with basal diet, Group II - rats fed diet supplemented with 10% processed walnut, Group III - rats fed diet supplemented with 10% raw walnut, Group IV - rats fed diet supplemented with 20% processed walnut and Group V - rats fed diet supplemented with 20% raw walnut. Behavioural studies (copulation tendency and anxiety) associated with sexual function, measurement of nitric oxide (NO) levels, adenosine deaminase (ADA), arginase and acetylcholinesterase (AChE) activities in the Corpus cavernosum as well as characterization of bioactive components of the nut were evaluated. Marked reductions in ADA and arginase activities and a concomitant increase (% inclusion dependent) in the level of NO as well as enhanced sexual behaviours were observed in rat fed supplemented walnut when compared to the control. Furthermore, analysis of the walnut using high performance liquid chromatography indicated the presence of some polyphenols. From our findings, it showed that walnut improves sexual behaviour and modulates activities of key enzymes relevant to erection in male rats which may justify its used in traditional medicine.

Coffee, caffeine, chlorogenic acid, and the purinergic system

Coffee is a drink prepared from roasted coffee beans and is lauded for its aroma and flavour. It is the third most popular beverage in the world. This beverage is known by its stimulant effect associated with the presence of methylxanthines. Caffeine, a purine-like molecule (1,3,7 trymetylxantine), is the most important bioactive compound in coffee, among others such as chlorogenic acid (CGA), diterpenes, and trigonelline. CGA is a phenolic acid with biological properties as antioxidant, anti-inflammatory, neuroprotector, hypolipidemic, and hypoglicemic. Purinergic system plays a key role inneuromodulation and homeostasis. Extracellular ATP, other nucleotides and adenosine are signalling molecules that act through their specific receptors, namely purinoceptors, P1 for nucleosides and P2 for nucleotides. They regulate many pathological processes, since adenosine, for instance, can limit the damage caused by ATP in the excitotoxicity from the neuronal cells. The primary purpose of this review is to discuss the effects of coffee, caffeine, and CGA on the purinergic system. This review focuses on the relationship/interplay between coffee, caffeine, CGA, and adenosine, and their effects on ectonucleotidases activities as well as on the modulation of P1 and P2 receptors from central nervous system and also in peripheral tissue.

Dietary supplementation of tiger nut alters biochemical parameters relevant to erectile function in l-NAME treated rats

Tiger nut tubers have been reportedly used for the treatment of erectile dysfunction (ED) in folk medicine without scientific basis. Hence, this study evaluated the effect of tiger nut on erectile dysfunction by assessing biochemical parameters relevant to ED in male rats by nitric oxide synthase (NOS) inhibitor, Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME) treatment. Rats were divided into five groups (n = 10) each: Control group; l-NAME plus basal diet; l-NAME plus Sildenafil citrate; diet supplemented processed tiger nut (20%) plus l-NAME;diet supplemented raw tiger nut (20%) plus l-NAME. l-NAME pre-treatment (40 mg/kg/day) lasted for 14 days. Arginase, acetycholinesterase (AChE) and adenosine deaminase (ADA) activities as well as nitric oxide levels (NO) in serum, brain and penile tissue were measured. l-NAME increased the activity of arginase, AChE and ADA and reduced NO levels. However, dietary supplementation with tiger nut caused a reduction on the activities of the above enzymes and up regulated nitric oxide levels when compared to the control group. The effect of tiger nut supplemented diet may be said to prevent alterations of the activities of the enzymes relevant in erectile function. Quercetin was revealed to be the most active component of tiger nut tuber by HPLC finger printing.

Comparative Evaluation of Antioxidative Properties and Effects of Aqueous Extracts of Cola Nitida and Vitex Doniana on Fe2+ - Generated Oxidative Stress in Rat Testes in Vitro

Male sexual dysfunction (MSD) might be produced by multifactorial determinants which include psychological disorders, androgen deficiencies, chronic medical conditions, vascular insufficiency, penile disease, pelvic surgery, neurological disorders, drugs, life style, aging and systemic diseases. This study sought to assess the antioxidant properties of the water-extractable component of the leaves of Black plum (Vitex doniana) and bark of Kola nut (Cola nitida),evaluate their effect on pro-oxidant generated lipid peroxidation in rat’s testes; and examine the effect on arginase which is among the major enzymes associated with Erectile dysfunction. The results of the total phenol, total flavonoid of aqueous extracts of Cola nitida and Vitex doniana revealed that Cola nitida (10.64 mgGAE/g) had significantly (P<0.05) more total phenol content than Vitex doniana (4.68 mgGAE/g). The result also revealed that Vitex doniana (2.1 mgQE/g) had significantly (P<0.05) higher total flavonoid content than Cola nitida (1.3 mgQE/g). Also, Vitex doniana (20.24 mgAEE/g) had significantly (p<0.05) higher reducing property than Cola nitida (17.43 mgAEE/g). The results of the 2, 2’-azino-bis (3-ethylbenthiazoline-6-sulphonic acid (ABTS*) radical mopping up capacity of the water extractable component of Vitex doniana and Cola nitida also showed that the extracts are able to scavenge ABTS* radicals, however, Vitex doniana (1.8 Mmol TEAC/100g) had significantly (P<0.05) higher ABTS* mopping up capability than Cola nitida (1.2 Mmol TEAC/100g). Furthermore, the DPPH* result revealed that Cola nitida and Vitex doniana extracts scavenged DPPH* radicals in a concentration-dependent pattern. However, Vitex doniana (IC50 = 1.28mg/ml) had a significantly (P<0.05) higher DPPH* mopping up capability than Cola nitida (IC50 = 0.83 mg/ml). Both extracts were able to inhibit FeSO4-generated lipid peroxidation at a dose-dependent manner; however, Vitex doniana (IC50 = 1.07 mg/ml) had a higher inhibitory action of Fe2+ induced lipid peroxidation than Cola nitida (IC50 = 1.01 mg/ml). Vitex doniana (IC50 = 0.38mg/ml) has the higher arginase inhibitory activity than Cola nitida (IC50 = 0.34mg/ml). High phenolic content and strong antioxidant properties could be part of the mechanisms through which the water extractable phytochemicals of Cola nitida (bark) and Vitex doniana (leaves) exhibits its preventive measure of erectile function. However, Vitex doniana displayed a stronger effect on Male reproductive function than Cola nitida.