Emmanuel Anyachukwu Irondi

Phenolic composition and inhibitory activity of Mangifera indica and Mucuna urens seeds extracts against key enzymes linked to the pathology and complications of type 2 diabetes

Objective To investigate the phenolic compounds composition and the inhibitory activity of Mangifera indica (M. indica) and Mucuna urens (M. urens) seeds extracts against some key enzymes (α-amylase, α-glucosidase and aldose reductase) implicated in the pathology and complications of type 2 diabetes in vitro. Methods Reverse phase chromatographic quantification of the major flavonoids and phenolic acids in the seeds extracts was carried out using high performance liquid chromatography coupled with diode array detection. The inhibitory activities of the seeds extracts against α-amylase and α-glucosidase were estimated using soluble starch and ρ-nitrophenylglucopyranoside as their respective substrates. Inhibition of aldose reductase activity by the extracts was assayed using partially purified lens homogenate of normal male rat as source of enzyme; inhibition of Fe2+-induced lipid peroxidation by extracts was tested in rat pancreas homogenate. Results The chromatography result revealed that extracts of both seeds had appreciable levels of some major flavonoids and phenolic acids of pharmacological importance, including gallic acid, chlorogenic acid, caffeic acid, ellagic acid, catechin, rutin, quercitrin, quercetin and kaempferol. Extracts of both seeds effectively inhibited α-amylase, α-glucosidase and aldose reductase activities in a dose-dependent manner, having inhibitory preference for these enzymes in the order of aldose reductase>α-glucosidase>α-amylase. With lower half-maximal inhibitory concentrations (IC50) against α-amylase, α-glucosidase, and aldose reductase, M. indica had stronger inhibitory potency against these enzymes than M. urens. Extracts of both seeds also inhibited Fe2+-induced lipid peroxidation in a dose-dependent pattern, with M. indica being more potent than M. urens. Conclusions The results obtained provide support for a possible use of M. indica and M. urens seeds in managing hyperglycemia and preventing the complications associated with it in type 2 diabetes.

Guava leaves polyphenolics-rich extract inhibits vital enzymes implicated in gout and hypertension in vitro -

Background/Aim: Elevated uric acid level, an index of gout resulting from the over-activity of xanthine oxidase (XO), increases the risk of developing hypertension. However, research has shown that plant-derived inhibitors of XO and angiotensin 1-converting enzyme (ACE), two enzymes implicated in gout and hypertension, respectively, can prevent or ameliorate both diseases, without noticeable side effects. Hence, this study characterized the polyphenolics composition of guava leaves extract and evaluated its inhibitory effect on XO and ACE in vitro. Materials and Methods: The polyphenolics (flavonoids and phenolic acids) were characterized using high-performance liquid chromatography (HPLC) coupled with diode array detection (DAD). The XO, ACE, and Fe2+-induced lipid peroxidation inhibitory activities, and free radicals (2,2-diphenylpicrylhydrazyl [DPPH]* and 2,2´-azino-bis-3-ethylbenzthiazoline-6-sulphonic [ABTS]*+) scavenging activities of the extract were determined using spectrophotometric methods. Results: Flavonoids were present in the extract in the order of quercetin > kaempferol > catechin > quercitrin > rutin > luteolin > epicatechin; while phenolic acids were in the order of caffeic acid > chlorogenic acid > gallic acids. The extract effectively inhibited XO, ACE and Fe2+-induced lipid peroxidation in a dose-dependent manner; having half-maximal inhibitory concentrations (IC50) of 38.24 ± 2.32 μg/mL, 21.06 ± 2.04 μg/mL and 27.52 ± 1.72 μg/mL against XO, ACE and Fe2+-induced lipid peroxidation, respectively. The extract also strongly scavenged DPPH* and ABTS*+. Conclusion: Guava leaves extract could serve as functional food for managing gout and hypertension and attenuating the oxidative stress associated with both diseases.

Antidiabetic effects of Mangifera indica Kernel Flour‐supplemented diet in streptozotocin‐induced type 2 diabetes in rats

Abstract Our previous report showed that Mangifera indica kernel flour (MIKF) is a rich source of pharmacologically important flavonoids and phenolic acids; and that its methanolic extract inhibits some key enzymes linked to the pathology and complications of type 2 diabetes (T2D) in vitro. Hence, this study evaluated the antidiabetic effects of 10% and 20% MIKF‐supplemented diets in T2D in rats. T2D was induced in rats using a high‐fat diet (HFD), low‐dose streptozotocin (HFD/STZ) model, by feeding the rats with HFD for 2 weeks followed by single dose administration of STZ (40 mg/kg body weight, intraperitoneally). The diabetic rats were later fed the MIKF‐supplemented diets, or administered with metformin (25 mg/kg b.w.) for 21 days; the control rats were fed basal diet during this period. Intake of the MIKF‐supplemented diets resulted in significant (P < 0.05) improvement in the fasting blood glucose, hepatic glycogen, glycosylated hemoglobin, lipid profile, plasma electrolytes, hepatic and pancreatic malonaldehyde, and the liver function markers of the diabetic rats, compared with the diabetic control rats. The ameliorative effect of 20% MIKF‐supplemented was comparable (P > 0.05) with that of metformin administration in the diabetic rats. It is concluded that M. indica kernel flour has antidiabetic effects in T2D rats, and could therefore be a promising nutraceutical therapy for the management of T2D and its associated complications.

Inhibitory effect of leaves extracts of Ocimum basilicum and Ocimum gratissimum on two key enzymes involved in obesity and hypertension in vitro.

Aim: To evaluate the phenolics composition and inhibitory effect of the leaves extracts of Ocimum basilicum and Ocimum gratissimum on two key enzymes (pancreatic lipase [PL] and angiotensin 1-converting enzyme [ACE]) involved in obesity and hypertension in vitro. Materials and Methods: The phenolics (flavonoids and phenolic acids) were quantified using high-performance liquid chromatography coupled with diode array detection. PL and ACE inhibitory effects; DPPH* and ABTS*+ scavenging activities of the extracts were tested using spectrophotometric methods. Results: O. basilicum had the following major phenolics: Rutin, quercetin, and quercitrin (flavonoids); caffeic, chlorogenic, and gallic acids (phenolic acids); while O. gratissimum had the following major phenolics: Rutin, quercitrin, and luteolin (flavonoids); ellagic and chlorogenic acids (phenolic acids). “Extracts of both plants inhibited PL and ACE; scavenged DPPH* in a dose-dependent manner”. O. gratissimum extract was more potent in inhibiting PL (IC50: 20.69 µg/mL) and ACE (IC50: 29.44 µg/mL) than O. basilicum (IC50: 52.14 µg/mL and IC50: 64.99 µg/mL, against PL and ACE, respectively). O. gratissimum also scavenged DPPH* and ABTS*+ more than O. basilicum. Conclusion: O. basilicum and O. gratissimum leaves could be used as functional foods for the management of obesity and obesity-related hypertension. However, O. gratissimum may be more effective than O. basilicum.

Blanching influences the phenolics composition, antioxidant activity, and inhibitory effect of Adansonia digitata leaves extract on α‐amylase, α‐glucosidase, and aldose reductase

Abstract Adansonia digitata (A. digitata) leaves serve as food and has several medicinal uses in many parts of the world. This study evaluated the influence of blanching on the phenolics composition, antioxidant activity, and inhibitory effect of methanol extract of A. digitata leaves on the activities of some key enzymes (α‐amylase, α‐glucosidase, and aldose reductase) implicated in type 2 diabetes (T2D) in vitro. Reverse‐phase HPLC analysis revealed that the leaves had appreciable levels of flavonoids and phenolic acids, including catechin, epicatechin, rutin, quercitrin, quercetin, kaempferol, and luteolin (flavonoids); gallic, chlorogenic, caffeic, and ellagic acids (phenolic acids). Blanching caused significant (P < 0.05) decrease in the flavonoids and phenolic acids contents; DPPH* (2,2 diphenyl‐1‐picrylhydrazyl radical) and ABTS*+ [2,2‐azinobis (3‐ethyl‐benzothiazoline‐6‐sulfonic acid) radical cation] scavenging ability; reducing power; and Fe2+‐induced lipid peroxidation inhibitory capacity of the extract. Similarly, the inhibitory effect of the extract on the activities of α‐amylase, α‐glucosidase, and aldose reductase was significantly (P < 0.05) reduced due to blanching. Thus, A. digitata leaves extract could be effective for the management of T2D due to its flavonoids and phenolic acids content, antioxidant properties, and inhibitory potency on the activities of α‐amylase, α‐glucosidase, and aldose reductase. However, blanching militated against the levels of these functional attributes of the leaves and, therefore, may not be recommended for their optimal retention.

Inhibitory Potential of Cocoa Leaves Polyphenolics-Rich Extract on Xanthine Oxidase and Angiotensin 1-Converting Enzyme

Abstract The over-activities of xanthine oxidase (XO) and angiotensin 1-converting enzyme (ACE) contribute to the pathogenesis of gout and hypertension, respectively. Polyphenolics and other natural inhibitors of XO and ACE have been shown to be useful for managing these two diseases. Therefore, this study evaluated the inhibitory potential of cocoa leaves polyphenolics-rich extract on XO and ACE, and its free radicals (2,2- diphenylpicrylhydrazyl [DPPH*] and 2,2´-azino-bis-3-ethylbenzthiazoline-6-sulphonic [ABTS*+]) scavenging ability, in vitro. The XO and ACE inhibition; and DPPH* and ABTS*+ scavenging assays were carried out using Spectrophotometric methods. Flavonoids and phenolic acids content of the extract was quantified using high performance liquid chromatrography coupled with diode array detection (HPLC-DAD). The extract strongly inhibited XO and ACE in a dose dependent pattern, with half-maximal inhibitory concentration (IC50) of 33.15 ± 1.84 μg/mL and 18.72 ± 1.05 μg/mL, respectively. The extract also scavenged DPPH* and ABTS*+. The HPLC-DAD analysis of the extract revealed the presence of flavonoids including catechin, rutin, quercetin and apigenin; and phenolic acids including gallic, caffeic and p-coumaric acids; with quercetin and caffeic acid as the most abundant flavonoid and phenolic acid , respectively. Cocoa leaves may be useful for preventing and managing gout and hypertension, through XO and ACE inhibition.

In Vitro Inhibitory Effects of Coconut Husk Extract on Some Enzymes Relevant to the Pathogenesis of Obesity, Gout and Hypertension

Abstract Coconut husk is a potential natural source of some important bioactive compounds with several health benefits. In this study, the inhibitory effects of polyphenolics-rich extract of coconut husk on pancreatic lipase (PL), xanthine oxidase (XO) and angiotensin 1-converting enzyme (ACE), being enzymes whose over-activities contribute to the pathogenesis of obesity, gout and hypertension, respectively, were investigated. Free radicals (DPPH* and ABTS*+) scavenging ability, and HPLC-DAD profile of the flavonoids and phenolic acids constituents of the extract were also evaluated. The extract strongly inhibited PL, XO and ACE in a dose-dependent pattern, with IC50 values of 12.34 ± 1.25 μg/mL, 26.20 ± 2.46 μg/mL and 17.64 ± 1.89 μg/mL, respectively. The extract effectively scavenged DPPH* and ABTS*+. The flavonoids in the extract were in the order of quercetin > apigenin > kaempferol > rutin; while the phenolic acids were in the order of p-coumaric acid > chlorogenic acid > gallic acid > caffeic acid. Hence, coconut husk may be a low-cost natural product for managing obesity, gout and hypertension, and alleviating oxidative stress; through inhibition of PL, XO and ACE, and scavenging of free radicals. The combined effects of the flavonoids and phenolic acids constituents of the husk may be responsible for these bioactivities.

Phenolic constituents, anti-radicals, and enzymes inhibitory potentials of Brachystegia eurycoma seeds: Effects of processing methods

ABSTRACT Impact of roasting and boiling on the phenolic constituents, anti-radicals, xanthine oxidase (XO), and angiotensin 1-converting enzyme (ACE) inhibitory potentials of Brachystegia eurycoma seeds (BES) was evaluated. Raw BES contained caffeic acid, ellagic acid, rutin, and quercetin as the predominant phenolics, and strongly scavenged DPPH* and ABTS*+, and inhibited XO and ACE. Both roasting and boiling resulted in decrease in the levels of phenolics and bioactivities of the seeds, but roasted seeds retained higher levels of the phenolics and the bioactivities than the boiled seeds. Roasting could be recommended as a valuable processing method for the retention of the phenolics and bioactivities of BES.