Ayokunle O. Ademosun

Shaddock peels (Citrus maxima) phenolic extracts inhibit α-amylase, α-glucosidase and angiotensin I-converting enzyme activities: A nutraceutical approach to diabetes management

In this study, the interactions of free and bound phenolic-rich extracts from shaddock peels (popular in folklore for the management of diabetes and hypertension) with α-amylase and α-glucosidase (key enzymes linked to type-2 diabetes) and angiotensin I-converting enzyme (ACE) (key enzyme linked to hypertension) were assessed. The free phenolics of shaddock (Citrus maxima) peels were extracted with 80% acetone, while the bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate; and their interaction with the enzymes were assessed. The phenolic extracts inhibited α-amylase, α-glucosidase and ACE enzyme activities in a dose-dependent manner; however, bound phenolics had significantly higher (P<0.05) α-amylase inhibitory activities, than free phenolics, which had significantly higher (P<0.05) ACE inhibitory activities. There was no significant difference (P>0.05) in their α-glucosidase inhibitory activities. The stronger inhibition of α-glucosidase when compared to α-amylase is of great pharmaceutical importance. The phenolic inhibited sodium nitroprusside induced lipid peroxidation in pancreas in a dose dependent manner. Therefore, free and bound phenolic extracts from shaddock peels could be used as nutraceutical for the management of hypertension and type-2 diabetes.

Antioxidative Properties and Effect of Quercetin and Its Glycosylated Form (Rutin) on Acetylcholinesterase and Butyrylcholinesterase Activities

This study sought to investigate the anticholinesterase and antioxidative properties of quercetin and its glycosylated conjugate, rutin. The in vitro inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities, inhibition of Fe2+-induced lipid peroxidation in rat’s brain homogenates, radicals scavenging, and Fe2+-chelating abilities of the flavonoids were investigated in vitro with concentrations of the samples ranging from 0.06 to 0.6 mM. Quercetin had significantly higher AChE and BChE inhibitory abilities than rutin. Quercetin also had stronger inhibition of Fe2+-induced lipid peroxidation in rat’s brain homogenates. Similarly, quercetin had higher radical scavenging abilities than rutin. Quercetin also had stronger Fe2+-chelating ability than rutin. The inhibition of cholinesterases and antioxidative properties are possible mechanisms by which the flavonoids can be used in the management of oxidative stress–induced neurodegeneration.

In Vitro Studies on the Antioxidant Property and Inhibition of α-Amylase, α-Glucosidase, and Angiotensin I-Converting Enzyme by Polyphenol-Rich Extracts from Cocoa (Theobroma cacao) Bean

Background. This study sought to investigate the antidiabetic and antihypertensive mechanisms of cocoa (Theobroma cacao) bean through inhibition of α-amylase, α-glucosidase, angiotensin-1 converting enzyme, and oxidative stress. Methodology. The total phenol and flavonoid contents of the water extractable phytochemicals from the powdered cocoa bean were determined and the effects of the extract on α-amylase, α-glucosidase, and angiotensin-1 converting enzyme activities were investigated in vitro. Furthermore, the radicals [1,1-diphenyl-2 picrylhydrazyl (DPPH), 2,2..-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), hydroxyl (OH), and nitric oxide (NO)] scavenging ability and ferric reducing antioxidant property of the extract were assessed. Results. The results revealed that the extract inhibited α-amylase (1.81 ± 0.22 mg/mL), α-glucosidase (1.84 ± 0.17 mg/mL), and angiotensin-1 converting enzyme (0.674 ± 0.06 mg/mL [lungs], 1.006 ± 0.08 mg/mL [heart]) activities in a dose-dependent manner and also showed dose-dependent radicals [DPPH (16.94 ± 1.34 mg/mL), NO (6.98 ± 0.886 mg/mL), OH (3.72 ± 0.26 mg/mL), and ABTS (15.7 ± 1.06 mmol/TEAC·g] scavenging ability. Conclusion. The inhibition of α-amylase, α-glucosidase, and angiotensin-1 converting enzyme activities by the cocoa bean extract could be part of the possible mechanism by which the extract could manage and/or prevent type-2 diabetes and hypertension.

Inhibition of Acetylcholinesterase Activity and Fe2+-Induced Lipid Peroxidation in Rat Brain In Vitro by Some Citrus Fruit Juices

This study sought to characterize the effects of some citrus fruit juices (shaddock [Citrus maxima], grapefruit [Citrus paradisii], lemon [Citrus limoni], orange [Citrus sinensis], and tangerine [Citrus reticulata]) on acetylcholinesterase activity in vitro. The total phenolic content, radical scavenging abilities, and inhibition of Fe(2+)-induced malondialdehyde (MDA) production in rats brain homogenate in vitro were also assessed. Orange had significantly (P<.05) higher phenolic content than the other juices. The juices scavenged 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radicals in a dose-dependent manner with orange having the highest scavenging ability. Furthermore, the juices inhibited Fe(2+)-induced MDA production in rat brain homogenate in a dose-dependent manner with shaddock having the highest inhibitory ability. Acetylcholinesterase activity was also inhibited in vitro by the juices in a dose-dependent manner. The inhibition of acetylcholinesterase activity and antioxidant properties of the citrus juices could make them a good dietary means for the management of Alzheimers disease.

Antioxidative Properties and Inhibition of Key Enzymes Relevant to Type-2 Diabetes and Hypertension by Essential Oils from Black Pepper

The antioxidant properties and effect of essential oil of black pepper (Piper guineense) seeds on α-amylase, α-glucosidase (key enzymes linked to type-2 diabetes), and angiotensin-I converting enzyme (ACE) (key enzyme linked to hypertension) were assessed. The essential oil was obtained by hydrodistillation and dried with anhydrous Na2SO4, and the phenolic content, radical [1,1-diphenyl-2 picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and nitric oxide (NO)] scavenging abilities as well as the ferric reducing antioxidant property (FRAP) and Fe2+-chelating ability of the essential oil were investigated. Furthermore, the effect on α-amylase, α-glucosidase, and ACE enzyme activities was also investigated. The characterization of the constituents was done using GC. The essential oil scavenged DPPH∗, NO∗, and ABTS∗ and chelated Fe2+. α-Pinene, β-pinene, cis-ocimene, myrcene, allo-ocimene, and 1,8-cineole were among the constituents identified by GC. The essential oil inhibited α-amylase, α-glucosidase, and ACE enzyme activities in concentration-dependent manners, though exhibiting a stronger inhibition of α-glucosidase than α-amylase activities. Conclusively, the phenolic content, antioxidant activity, and inhibition of α-amylase, α-glucosidase, and angiotensin-1 converting enzyme activities by the essential oil extract of black pepper could be part of the mechanism by which the essential oil could manage and/or prevent type-2 diabetes and hypertension.

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.

Inhibition of enzymes linked to type-2 diabetes and hypertension by essential oils from peels of orange and lemon

ABSTRACT This study was designed to evaluate and compare the interactions of essential oils from orange (Citrus sinensis [L.] Osbeck) and lemon (Citrus limon) peels on enzymes linked to type-2 diabetes (α-amylase and α-glucosidase) and hypertension (angiotensin-I-converting enzyme [ACE]). The essential oils were obtained from the peels by hydrodistillation and were passed over anhydrous sodium sulphate. The interaction of the oil on α-amylase, α-glucosidase, and ACE activities was subsequently determined. The results revealed that the essential oils inhibited α-amylase and α-glucosidase activities. However, lemon peel (IC50 = 8.16 µg/mL and 7.56 µg/mL) essential oil exhibited stronger inhibitory activity on α-amylase and α-glucosidase activities compared to orange peels (IC50 = 11.51 µg/mL and 11.53 µg/mL), respectively. Similarly, both essential oils reduced the activity of ACE. Moreover, lemon peel (IC50 = 26.17 µg/mL) essential oil showed higher inhibitory effect compared to orange peel (IC50 = 31.79 µg/mL). Our findings revealed that essential oils from lemon and orange peels are potential antidiabetic and antihypertensive agents. Moreover, essential oil from lemon peels was more potent than orange peels.

Anticholinesterase and antioxidative properties of water-extractable phytochemicals from some citrus peels.

Abstract Background: Aqueous extracts from citrus peels are used in many rural communities in Nigeria in treating various degenerative conditions, although the scientific basis for its use has not been well established. This study sought to investigate the anticholinesterase and antioxidant properties of aqueous extracts from some citrus peels [orange (Citrus sinensis), grapefruit (Citrus paradisii), and shaddock (Citrus maxima)]. Methods: The effects of the extracts on acetylcholinesterase (AChE) activity, as well as Fe2+-induced malondialdehyde (MDA) production in vitro, were investigated. The total phenolic, flavonoid content, and antioxidant activities as typified by 1,1-diphenyl-2 picrylhydrazyl (DPPH) free radical scavenging ability and hydroxyl (OH) radicals scavenging abilities were also investigated. Results: The results revealed that orange peels had the highest total phenol content followed by grapefruit peels, whereas shaddock peels had the least. The extracts inhibited AChE activity in a dose-dependent manner, although there is no significant difference (p>0.05) in their inhibitory abilities of the peels. The extracts exhibited antioxidant activities as typified by their radical (DPPH· and OH·) scavenging abilities as well as the inhibition of Fe2+-induced lipid peroxidation in rat’s brain in vitro. Conclusions: The anticholinesterase activity and inhibition of MDA production by the aqueous extracts of the peels, as well as other antioxidant activities, could make the peels a good dietary means for the management of oxidative-mediated neurodegenerative disorders.

In vitro inhibition of phosphodiesterase-5 and arginase activities from rat penile tissue by two Nigerian herbs (Hunteria umbellata and Anogeissus leiocarpus)

Abstract Background: Anogeissus leiocarpus and Hunteria umbellata have been reportedly used in traditional medicine for the management of erectile dysfunction (ED). However, the scientific basis for their use has not been well established. Therefore, this study was designed to investigate the inhibitory effects of water extractable phytochemicals of H. umbellata and A. leiocarpus on phosphodiesterase-5 (PDE-5) and arginase as well as pro-oxidants induced lipid peroxidation in rat penile tissue. Methods: The effects of the extracts on important enzymes (PDE-5 and arginase) linked with ED and pro-oxidants (Fe2+ and sodium nitroprusside) induced lipid peroxidation were investigated. Also, radicals scavenging and metal chelating abilities were determined. In addition, phenolic contents were determined and characterized using HPLC. Results: The results showed that both extracts inhibited PDE-5 and arginase activities in a dose-dependent manner. Inhibitory property of A. leiocarpus (IC50 – 174.19 μg/mL) was significantly better (p<0.05) than that of H. umbellata (IC50 – 537.72 μg/mL) in PDE-5 assay. The extracts were potent inhibitors of arginase than PDE-5, and these extracts were equally potent in inhibiting arginase. Furthermore, Fe2+ and sodium nitroprusside caused a significant increase in malondialdehyde content; however, both extracts reduced malondialdehyde level in concentration-dependent manner. It is noteworthy that both extracts scavenged radicals (OH* and ABTS*) and chelated Fe2+. HPLC analysis revealed abundance of rutin, chlorogenic acid, gallic acid, caffeic acid, and quercetin, among others. Conclusions: The ability of the extracts to inhibit PDE-5, arginase and pro-oxidant induced lipid peroxidation, and chelate metal might suggest their folkloric use for the management of ED.

Quercetin and Its Role in Chronic Diseases

Quercetin, a member of the flavonoid class of polyphenol, is one of the most abundantly distributed flavonoids found in various food sources such as fruits, vegetables, nuts, wine and seeds. Quercetin and quercetin-rich foods have been reported to have wide range of health promoting effects, especially in the prevention and management of several diseases; however, the subject of its solubility and bioavailability has limited its use. This section will therefore, consider quercetin as a food-rich flavonoid, the various food sources, the limitations in its use and new approaches at improving its solubility and bioavailability. The therapeutic potentials of quercetin at the prevention/management of some degenerative diseases such as diabetes, hypertension and neurodegenerative diseases, as well as the underlying biochemical mechanisms such as free radical scavenging and enzyme inhibition will also be discussed.