Sunday I. Oyeleye

Phenolic Composition and Evaluation of Methanol and Aqueous Extracts of Bitter Gourd (Momordica charantia L) Leaves on Angiotensin-I-Converting Enzyme and Some Pro-oxidant-Induced Lipid Peroxidation In Vitro

This study sought to assess the effects of bitter gourd leaf extracts (methanol and aqueous) on enzyme linked with hypertension (angiotensin-I-converting enzyme and some pro-oxidants (iron sulfate, sodium nitroprusside, and cisplatin]–induced lipid peroxidation in rat kidney homogenates. Chromatographic analysis of the extract was done using high-performance liquid chromatography–diode array detection. The results revealed that methanol extract (IC50 = 109.63 µg/mL) had significantly (P < .05) higher angiotensin-I converting enzyme inhibitory activity than aqueous extract (IC50 = 182.95 µg/mL). Similarly, methanol extract had significantly (P < .05) higher inhibitory effect on Fe2+- and cisplatin-induced lipid peroxidation than aqueous extract. However, there was no significant (P > .05) difference in the inhibition of sodium nitroprusside–induced lipid peroxidation of both extracts. High-performance liquid chromatography–diode array detection analysis revealed the presence of quercetin, caffeic, gallic, and chlorogenic acids in the leaf. Thus, inhibition of angiotensin-I converting enzyme activity and the antioxidant properties of the extracts could be linked to the presence of phenolic phytochemicals.

Distribution of Phenolic Contents, Antidiabetic Potentials, Antihypertensive Properties, and Antioxidative Effects of Soursop (Annona muricata L.) Fruit Parts In Vitro

Soursop fruit has been used in folklore for the management of type-2 diabetes and hypertension with limited information on the scientific backing. This study investigated the effects of aqueous extracts (1 : 100 w/v) of Soursop fruit part (pericarp, pulp, and seed) on key enzymes linked to type-2 diabetes (α-amylase and α-glucosidase) and hypertension [angiotensin-I converting enzyme (ACE)]. Radicals scavenging and Fe2+ chelation abilities and reducing property as well as phenolic contents of the extracts were also determined. Our data revealed that the extracts inhibited α-amylase and α-glucosidase and ACE activities dose-dependently. The effective concentration of the extract causing 50% antioxidant activity (EC50) revealed that pericarp extract had the highest α-amylase (0.46 mg/mL), α-glucosidase (0.37 mg/mL), and ACE (0.03 mg/mL) inhibitory activities while the seed extract had the least [α-amylase (0.76 mg/mL); α-glucosidase (0.73 mg/mL); and ACE (0.20 mg/mL)]. Furthermore, the extracts scavenged radicals, reduced Fe3+ to Fe2+, and chelated Fe2+. The phenolic contents in the extracts ranged from 85.65 to 560.21 mg/100 g. The enzymes inhibitory and antioxidants potentials of the extracts could be attributed to their phenolic distributions which could be among the scientific basis for their use in the management of diabetes and hypertension. However, the pericarp appeared to be most promising.

Essential Oil from Clove Bud (Eugenia aromatica Kuntze) Inhibit Key Enzymes Relevant to the Management of Type-2 Diabetes and Some Pro-oxidant Induced Lipid Peroxidation in Rats Pancreas in vitro

The inhibition of enzymes involved in the breakdown of carbohydrates is considered a therapeutic approach to the management of type-2 diabetes. This study sought to investigate the effects of essential oil from clove bud on α-amylase and α-glucosidase activities. Essential oil from clove bud was extracted by hydrodistillation, dried with anhydrous Na2SO4 and characterized using gas chromatography-mass spectrometry (GC-MS). The effects of the essential oil on α-amylase and α-glucosidase activities were investigated. The antioxidant properties of the oil and the inhibition of Fe(2+) and sodium nitroprusside-induced malondialdehyde (MDA) production in rats pancreas homogenate were also carried out. The essential oil inhibited α-amylase (EC50=88.9 μl/L) and α-glucosidase (EC50=71.94 μl/L) activities in a dose-dependent manner. Furthermore, the essential oil inhibited Fe(2+) and SNP-induced MDA production and exhibited antioxidant activities through their NO*, OH*, scavenging and Fe(2+)- chelating abilities. The total phenolic and flavonoid contents of the essential oil were 12.95 mg/g and 6.62 mg/g respectively. GC-MS analysis revealed the presence of α-pinene, β-pinene, neral, geranial, gamma terpinene, cis-ocimene, allo ocimene, 1,8-cineole, linalool, borneol, myrcene and pinene-2-ol in significant amounts. Furthermore, the essential oils exhibited antioxidant activities as typified by hydroxyl (OH) and nitric oxide (NO)] radicals scavenging and Fe(2+)-chelating abilities. The inhibition of α-amylase and α-glucosidase activities, inhibition of pro-oxidant induced lipid peroxidation in rat pancreas and antioxidant activities could be possible mechanisms for the use of the essential oil in the management and prevention of oxidative stress induced type-2 diabetes.

Modulation of some markers of erectile dysfunction and malonaldehyde levels in isolated rat penile tissue with unripe and ripe plantain peels: identification of the constituents of the plants using HPLC

Abstract Context: Plantain fruit pulp has been used as a natural remedy to manage erectile dysfunction (ED) in traditional medicine. However, the potency of the peel has not been examined with respect to ED management. Objective: This study investigated and compared the inhibitory potential of unripe (UPP) and ripe (RPP) plantain peels on some enzymes associated with ED and Fe2+-induced oxidative stress in albino rat penile homogenate in vitro. Materials and method: Aqueous extract of the peels was prepared and the effect on phosphodiesterase-5 (PDE-5), arginase, acetylcholinesterase (AChE), angiotensin-I converting enzyme (ACE) and Fe2+-induced malonyladehyde in isolated albino rat penile homogenate were investigated. Phenolic constituents of the peels powder were characterized using high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). Result: Extract from UPP had higher PDE-5 (IC50 = 3.10 μg/mL), arginase (IC50 = 0.96 μg/mL), AChE (IC50 = 6.30 μg/mL) and ACE (IC50 = 0.41 μg/mL) inhibitory ability compared with RPP (PDE-5, IC50 = 4.33 μg/mL; arginase, IC50 = 1.34 μg/mL; AChE, IC50 = 8.64 μg/mL; ACE, IC50 = 0.63 μg/mL). The extract from UPP also had higher inhibition of Fe2+-induced lipid peroxidation. HPLC-DAD analysis revealed that gallic and caffeic acids, rutin, quercitrin and quercetin were abundant in UPP, while catechin, kaempferol, chlorogenic and ellagic acids were the dominant phenolic compounds in RPP. Discussion and conclusion: Inhibition of enzymes associated with ED and lipid peroxidation could be linked with the phenolic compounds. However, UPP appeared to be more potent.

Antioxidant and Antihyperglycemic Properties of Three Banana Cultivars (Musa spp.)

Background. This study sought to investigate the antioxidant and antihyperglycemic properties of Musa sapientum (Latundan banana) (MSL), Musa acuminata (Cavendish banana) (MAC), and Musa acuminate (Red Dacca) (MAR). Materials and Methods. The sugar, starch, amylose, and amylopectin contents and glycemic index (GI) of the three banana cultivars were determined. Furthermore, total phenol and vitamin C contents and α-amylase and α-glucosidase inhibitory effects of banana samples were also determined. Results. MAC and MAR had the highest starch, amylose, and amylopectin contents and estimated glycemic index (eGI) with no significant different while MSL had the lowest. Furthermore, MAR (1.07 mg GAE/g) had a higher total phenol content than MAC (0.94 mg GAE/g) and MSL (0.96 mg GAE/g), while there was no significant difference in the vitamin C content. Furthermore, MAR had the highest α-amylase (IC50 = 3.95 mg/mL) inhibitory activity while MAC had the least (IC50 = 4.27 mg/mL). Moreover, MAC and MAR inhibited glucosidase activity better than MSL (IC50 3.47 mg/mL). Conclusion. The low sugar, GI, amylose, and amylopectin contents of the three banana cultivars as well as their α-amylase and α-glucosidase inhibitory activities could be possible mechanisms and justification for their recommendation in the management of type-2 diabetes.

Aqueous extracts of avocado pear (Persea americana Mill.) leaves and seeds exhibit anti-cholinesterases and antioxidant activities in vitro.

Abstract Background: Avocado pear (Persea americana Mill.) leaves and seeds are used in traditional medicine for the treatment/management of Alzheimer disease (AD); however, information on the mechanism of actions is limited. This study sought to investigate the effect of P. americana leaf and seed aqueous extracts on some enzymes linked with AD (acetylcholinesterase [AChE] and butyrylcholinesterase [BChE] activities) and their antioxidant potentials in vitro. Methods: The inhibitory effects of extracts on AChE and BChE activities and antioxidant potentials (inhibition of Fe2+- and sodium nitroprusside-induced thiobarbiturate reactive species [TBARS] production in rat brain homogenates, radicals [1,1-diphenyl-2-picrylhydrazyl, hydroxyl, and nitric oxide] scavenging and iron [Fe] chelation abilities) were investigated. Phenolic content and phytochemical screening were carried out. Alkaloid profile was also determined using gas chromatography coupled with flame ionization detector (GC-FID). Results: The extracts inhibited AChE and BChE activities and prooxidant-induced TBARS production in a dose-dependent manner, with the seed extract having the highest inhibitory effect and the leaf extract exhibiting higher phenolic content and radical scavenging abilities, but lower Fe chelation ability compared with that of the seed. The phytochemical screening revealed the presence of saponins, alkaloids, and terpenoids in both extracts, whereas the total alkaloid profile was higher in the seed extract than in the leaf extract, as revealed by GC-FID. Conclusions: The anti-cholinesterase and antioxidant activities of avocado leaf and seed could be linked to their phytoconstituents and might be the possible mechanisms underlying their use as a cheap and natural treatment/management of AD. However, these extracts should be further investigated in vivo.

Phenolic profile and Enzyme Inhibitory activities of Almond (Terminalia catappa) leaf and Stem bark

ABSTRACT Almond (Terminalia catappa) is a species used in Nigerian folkloric medicine because of its antihypertensive property. In this study, the acetylcholinesterase, arginase, phosphodiesterase-5 and angiotensin-1-converting enzyme inhibition and antioxidant properties of the phenolic-rich extracts from almond leaf and stem bark were determined. The chemical composition was evaluated using high-performance liquid chromatography. The total phenol and flavonoid contents were estimated and the antihypertensive potential was estimated by the determination of acetylcholinesterase, arginase, phosphodiesterase-5 and angiotensin-1-converting enzyme inhibition in vitro. Three assays were used for the evaluation of antioxidant properties of the extracts. Eleven and eight phenolic compounds were detected in leaf and stem bark respectively. The phenolic-rich extracts showed remarkable enzyme inhibition activity in concentration dependent manner, with high antioxidant activities. Almond leaf and stem bark can serve as potential natural source for the development of a novel antihypertensive agent.

Alteration of starch hydrolyzing enzyme inhibitory properties, antioxidant activities, and phenolic profile of clove buds (Syzygium aromaticum L.) by cooking duration

Abstract This study assessed the effect of cooking duration on starch hydrolyzing enzyme (α‐amylase and α‐glucosidase) activities, antioxidant (1,1‐diphenyl‐2 picrylhydrazyl [DPPH*], hydroxyl [OH*] radicals scavenging abilities and reducing power) properties, and phenolic profile of clove buds. Clove buds (raw) were cooked for 10 (SC 10) and 20 min (SC 20) and subsequently, their effects were assessed on enzyme activities, antioxidant properties, and phenolic profile. Inhibition of α‐amylase and α‐glucosidase activities and radicals scavenging abilities were altered by cooking in the trend; raw < SC 10 > SC 20, with IC 50 values ranging from 0.25 to 0.52 mg/mL and 0.10 to 1.50 mg/mL respectively. HPLC phenolic profile of the clove buds revealed significant (P < 0.05) changes in the amount of chlorogenic acid, quercitrin, quercetin, and kaempferol at different cooking duration. Thus, cooking duration may alter the phenolic compositions and nutraceutical potentials of clove bud by activation and/or deactivation of redox‐active metabolites.

Effect of caffeine, caffeic acid and their various combinations on enzymes of cholinergic, monoaminergic and purinergic systems critical to neurodegeneration in rat brain— In vitro

HIGHLIGHTSIn vitro neuromodulatory effects of proportion of caffeine to caffeic acid as obtained in most foods were investigated.These combinations modulate activities of some enzymes critical to neurodegeneration in rat brain structures.The combinations also exhibited Fe2+ and Cu2+ chelating abilities.However, a higher proportion of caffeine to caffeic acid produced significantly higher enzyme modulatory effects.These opined that food rich in higher caffeine‐caffeic acid ratio could offer more neuroprotective potentials. ABSTRACT Caffeine and caffeic acid are two bioactive compounds that are present in plant foods and are major constituent of coffee, cocoa, tea, cola drinks and chocolate. Although not structurally related, caffeine and caffeic acid has been reported to elicit neuroprotective properties. However, their different proportional distribution in food sources and possible effect of such interactions are not often taken into consideration. Therefore, in this study, we investigated the effect of caffeine, caffeic acid and their various combinations on activities of some enzymes [acetylcholinesterase (AChE), monoamine oxidase (MAO) ecto‐nucleoside triphosphate diphosphohydrolase (E‐NTPase), ecto‐51‐nucleotidase (E‐NTDase) and Na+/K+ ATPase relevant to neurodegeneration in vitro in rat brain. The stock concentration of caffeine and caffiec acid and their various proportional combinations were prepared and their interactions with the activities of these enzymes were assessed (in vitro) in different brain structures. The Fe2+ and Cu2+ chelating abilities of the samples were also investigated. The results revealed that caffeine, caffeic acid and their various combinations exhibited inhibitory effect on activities of AChE, MAO, E‐NTPase and E‐NTDase, but stimulatory effect on Na+/K+ ATPase activity. The combinations also exhibited Fe2+ and Cu2+ chelating abilities. Considering the various combinations, a higher caffeine to caffeic acid ratio produced significantly highest enzyme modulatory effects; these were significantly lower to the effect of caffeine alone but significantly higher than the effect of caffeic acid alone. These findings may provide new insight into the effect of proportional combination of these bioactive compounds as obtained in many foods especially with respect to their neuroprotective effects.

Polyphenolic compositions and in vitro angiotensin-I-converting enzyme inhibitory properties of common green leafy vegetables: A comparative study

This study compared the phenolic compositions of common green leafy vegetable extracts from Vernonia amygdalina (VA), Telfairia occidentalis (TO), Talinium triangulare (TT), and Amaranthus hybridus (AH) and their effects on the angiotensin-I-converting enzyme (ACE) and cisplatin-induced malonylaldehyde (MDA) production in an isolated rat kidney homogenate. HPLC confirmed the presence of phenolic compounds in the extracts. Furthermore, all extracts inhibited ACE activity dosedependently; however, the extract from VA exhibited the highest ACE activity while TT exhibited the least. Incubation of the kidney homogenate with 1mM cisplatin caused an increase in MDA production; however, all the extracts inhibited the level of MDA produced. Nevertheless, VA extract exhibited the highest inhibition. These activities of the vegetable extracts could be attributed to their phenolic compositions and may suggest some possible mechanism of the actions. However, VA appeared to be the most potent among the vegetables tested.