Mechanisms of inhibition of advanced glycation end-products (AGEs) and α-glucosidase by Heliotropium bacciferum: Spectroscopic and molecular docking analysis

Diabetes mellitus is characterized by hyperglycemia that makes insulin more prone to glycation and form advanced glycation end products (AGEs). Here, we report the effect of glyoxal (GO) on the formation of AGEs using human insulin as model protein and their structural modifications. The present investigation also reports the anti-AGE potential of Heliotropium bacciferum (Leaf) extracts. The phytochemical analysis of H. bacciferum revealed that free phenolic extract contains higher amount of total phenolic (3901.58 ± 17.06 mg GAE/100 g) and total flavonoid content (30.41 ± 0.32 mg QE/100 g) when compared to bound phenolic extract. Naringin and caffeic acid were identified as the major phenolic ingredients by UPLC-PAD method. Furthermore, bound phenolics extract showed significantly higher DPPH and superoxide radicals scavenging activity (IC50 17.53 ± 0.36 μg/mL and 0.306 ± 0.038 mg/ mL, respectively) (p ≤ 0.05). Besides, the bound phenolics extract also showed significant (p ≤ 0.05) chelating power (IC50 0.063) compared to free phenolic extract. In addition, bound phenolic extract could efficiently trap GO under physiological conditions. Spectroscopic investigation of GO-modified insulin illustrated changes in the tertiary structure of insulin and formation of AGEs. On the other hand, no significant alteration in secondary structure was observed by far UV-CD measurement. Furthermore, H. bacciferum extract inhibited α-glucosidase activity and AGEs formation implicated in diabetes. Molecular docking analysis depicted that GO bind with human insulin in both chains and forms a stable complex with TYR A: 14, LEU A:13, ASN B:3, SER A:12 amino acid residues with binding energy of - 2.53 kcal/mol. However, caffeic acid binds to ASN A:18 and GLU A:17 residues of insulin with lower binding energy of -4.67 kcal/mol, suggesting its higher affinity towards human insulin compared to GO. Our finding showed promising activity of H. bacciferum against AGEs and its complications. The major phenolics like caffeic acid, naringin and their derivatives could be exploited for the drug development for management of AGEs in diabetes.

Design, synthesis, and evaluation of 2,2'-bipyridyl derivatives as bifunctional agents against Alzheimer's disease

Alzheimer's disease (AD) is a complex multifactorial neurodegenerative disease. Metal ion dyshomeostasis and Aβ aggregation have been proposed to contribute to AD progression. Metal ions can bind to Aβ and promote Aβ aggregation, and ultimately lead to neuronal death. Bifunctional (metal chelation and Aβ interaction) compounds are showing promise against AD. In this work, eleven new 3,3'-diamino-2,2'-bipyridine derivatives 4a-4k were synthesized, and evaluated as bifunctional agents for AD treatment. In vitro Aβ aggregation inhibition assay confirmed that most of the synthesized compounds exhibited significant self-induced Aβ_1-42 aggregation inhibition. Among them, compound 4d displayed the best inhibitory potency of self-induced Aβ_1-42 aggregation with IC₅₀ value of 9.4 µM, and it could selectively chelate with Cu²⁺ and exhibited 66.2% inhibition of Cu²⁺-induced Aβ_1-42 aggregation. Meanwhile, compound 4d showed strong neuroprotective activity against Aβ_1-42 and Cu²⁺-treated Aβ_1-42 induced cell damage. Moreover, compound 4d in high dose significantly reversed Aβ-induced memory impairment in mice.

Competent antioxidant and antiglycation properties of zinc oxide nanoparticles (ZnO-NPs) phyto-fabricated from aqueous leaf extract of Boerhaavia erecta L

During the present century, plant-based zinc oxide nanoparticles (ZnO-NPs) are exploited extensively for their vast biological properties due to their unique characteristic features and eco-friendly nature. Diabetes is one of the fast-growing human diseases/abnormalities worldwide, and the need for new/ novel antiglycation products is the need of the hour. The study deals with the phyto-fabrication of ZnO-NPs from Boerhaavia erecta, a medicinally important plant, and to evaluate their antioxidant and antiglycation ability in vitro. UV-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to characterize the phyto-fabricated ZnO-NPs. The characterization of nanoparticles revealed that the particles showed an absorption peak at 362 nm and band gap energy of 3.2 eV, approximately 20.55 nm in size, with a ZnO elemental purity of 96.61%. The synthesized particles were found agglomerated when observed under SEM, and the FT-IR studies proved that the phyto-constituents of the extract involved during the different stages (reduction, capping, and stabilization) of nanoparticles synthesis. The antioxidant and metal chelating activities confirmed that ZnO-NPs could inhibit the free radicals generated, which was dose-dependent with an IC₅₀ value between 1.81 and 1.94 mg mL^-1, respectively. In addition, the phyto-fabricated nanoparticles blocked the formation of advanced glycation end products (AGEs) as noticed through inhibition of Amadori products, trapping of reactive dicarbonyl intermediate and breaking the cross-link of glycated protein. It was also noted that the phyto-fabricated ZnO-NPs significantly prevented the damage of red blood corpuscles (RBCs) induced by MGO. The present study's findings will provide an experimental basis for exploring ZnO-NPs in diabetes-related complications.

Phytochemical analysis and anticholinesterase activity of aril of Myristica fragrans Houtt

In this study, the ethyl acetate fraction of Myristica fragrans Houtt. was investigated for its in vitro anticholinesterase activity as well as neuroprotectivity against H₂O₂-induced cell death in PC12 neuronal cells and the ability to chelate bio-metals (Zn²⁺, Fe²⁺, and Cu²⁺). The fraction was inactive toward acetylcholinesterase (AChE); however, it inhibited the butyrylcholinesterase (BChE) with IC₅₀ value of 68.16 µg/mL, compared with donepezil as the reference drug (IC₅₀ = 1.97 µg/mL) via Ellman's method. It also showed good percentage of neuroprotection (86.28% at 100 µg/mL) against H₂O₂-induced neurotoxicity and moderate metal chelating ability toward Zn²⁺, Fe²⁺, and Cu²⁺. The phytochemical study led to isolation and identification of malabaricone A (1), malabaricone C (2), 4-(4-(3,4-dimethoxyphenyl)-2,3-dimethylbutyl)benzene-1,2-diol (3), nectandrin B (4), macelignan (5), and 4-(4-(benzo[d][1,3]dioxol-5-yl)-1-methoxy-2,3-dimethylbutyl)-2-methoxyphenol (6) which were assayed for their cholinesterase (ChE) inhibitory activity. Compounds 1 and 3 were not previously reported for M. fragrans. Among isolated compounds, compound 2 showed the best activity toward both AChE and BChE with IC₅₀ values of 25.02 and 22.36 μM, respectively, compared with donepezil (0.07 and 4.73 μM, respectively).

On the free radical scavenging and metallic ion chelating activities of pyridoxal - Could the pro-oxidant risk be competitive?

Primary and secondary antioxidant activities of pyridoxal have been investigated by using density functional theory (DFT) at the M05-2X level combined with 6-311++G(d,p) basis set for non-metallic atoms and LanL2DZ for metallic ions. The former has been examined by its free radical scavenging activity towards HOO^●, HO^●, and NO₂^●via different mechanisms including formal hydrogen transfer (FHT), proton transfer (PT), single electron transfer (SET), and radical adduct formation (RAF). The latter has been accomplished through its transition metal-chelating ability with Fe(III)/Fe(II) and Cu(II)/Cu(I) ions. The results show that pyridoxal illustrates as an efficient radical scavenger, especially, for HO^● and NO₂^● in water. The overall rate constants (k_overall) for the reactions with HOO^●, HO^●, and NO₂^● radicals are 1.30 × 10⁴, 5.76 × 10⁹, and 1.43 × 10⁹ M^-1s^-1, respectively. The SET from the anionic state is the most dominant for the HOO^● and NO₂^● scavenging reactions, while both RAF and SET contribute largely to the reaction with highly reactive HO^● radicals. Moreover, the anionic form of pyridoxal demonstrates a better role as a metal chelator than the neutral. However, the pro-oxidant risks of the formed complexes could be observed if there are superoxide radical anion (O₂^●-) and ascorbate (Asc^-) in aqueous media.

Imidazolylacetophenone oxime-based multifunctional neuroprotective agents: Discovery and structure-activity relationships

Alzheimer's disease (AD) possesses a complex pathogenetic mechanism. Nowadays, multitarget agents are considered to have potential in effectively treating AD via triggering molecules in functionally complementary pathways at the same time. Here, based on the screening (∼1400 compounds) against neuroinflammation, an imidazolylacetophenone oxime ether (IOE) was discovered as a novel hit. In order to obtain SARs, a series of imidazolylacetophenone oxime derivatives were constructed, and their C=N bonds were confirmed as the Z configuration by single crystals. These derivatives exhibited potential multifunctional neuroprotective effects including anti-neuroinflammatory, antioxidative damage, metal-chelating, inhibition of acetylcholinesterase (AChE) properties. Among these derivatives, compound 12i displayed the most potent inhibitory activity against nitric oxide (NO) production with EC₅₀ value of 0.57 μM 12i can dose-dependently suppress the expression of iNOS and COX-2 but not change the expression of HO-1 protein. Moreover, 12i exhibited evidently neuroprotective effects on H₂O₂-induced PC12 cells damage and ferroptosis without cytotoxicity at 10 μM, as well as selectively metal chelating properties via chelating Cu²⁺. In addition, 12i showed a mixed-type inhibitory effect on AChE in vitro. The structure-activity relationships (SARs) analysis indicated that dioxolane groups on benzene ring and rigid oxime ester can improve the activity. Parallel artificial membrane permeation assay (PAMPA) also verified that 12i can overcome the blood-brain barrier (BBB). Overall, this is the first report on imidazolylacetophenone oxime-based multifunctional neuroprotective effects, suggesting that this type of compounds might be novel multifunctional agents against AD.

Advances in the development of HIV integrase strand transfer inhibitors

HIV-1 integrase (IN) is a key enzyme in viral replication that catalyzes the covalent integration of viral cDNA into the host genome. Currently, five HIV-1 IN strand transfer inhibitors (INSTIs) are approved for clinical use. These drugs represent an important addition to the armamentarium for antiretroviral therapy. This review briefly illustrates the development history of INSTIs. The characteristics of the currently approved INSTIs, as well as their future perspectives, are critically discussed.

Synthesis and evaluation of novel arylisoxazoles linked to tacrine moiety: in vitro and in vivo biological activities against Alzheimer's disease

Alzheimer's disease (AD) is now ranked as the third leading cause of death after heart disease and cancer. There is no definite cure for AD due to the multi-factorial nature of the disease, hence, multi-target-directed ligands (MTDLs) have attracted lots of attention. In this work, focusing on the efficient cholinesterase inhibitory activity of tacrine, design and synthesis of novel arylisoxazole-tacrine analogues was developed. In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition assay confirmed high potency of the title compounds. Among them, compounds 7l and 7b demonstrated high activity toward AChE and BChE with IC₅₀ values of 0.050 and 0.039 μM, respectively. Both compounds showed very good self-induced Aβ aggregation and AChE-induced inhibitory activity (79.4 and 71.4% for compound 7l and 61.8 and 58.6% for compound 7b, respectively). Also, 7l showed good anti-BACE1 activity with IC₅₀ value of 1.65 µM. The metal chelation test indicated the ability of compounds 7l and 7b to chelate biometals (Zn²⁺, Cu²⁺, and Fe²⁺). However, they showed no significant neuroprotectivity against Aβ-induced damage in PC12 cells. Evaluation of in vitro hepatotoxicity revealed comparable toxicity of compounds 7l and 7b with tacrine. In vivo studies by Morris water maze (MWM) task demonstrated that compound 7l significantly reversed scopolamine-induced memory deficit in rats. Finally, molecular docking studies of compounds 7l and 7b confirmed establishment of desired interactions with the AChE, BChE, and BACE1 active sites.

Influence of Kersting's (Kerstingiella geocarpa) groundnut proteins on the physicochemical, bioactive properties and storage stability of orange juice

Sweet orange ranks as one of the most acceptable fruit juices across the globe as it offers a healthy choice and pleasant taste to a wide spectrum of consumers. This makes it a promising vehicle for conveying functional ingredients into the human body. The present study was designed to produce functional orange juice by incorporating Kersting's groundnut proteins (isolate and hydrolysates) at different proportions (0.6, 0.8 and 1.0 w/v) into freshly produced sweet orange juice. The sample formulations were further analysed for changes in their physicochemical (pH, titratable acidity, total soluble sugars, ascorbic acid and total phenol content), sensory (appearance, colour, flavour, mouthfeel and overall acceptability), antioxidant (radical scavenging, metal chelating, ferric ion-reducing abilities, DPPH, total antioxidant) and antidiabetic (inhibition of α-amylase and α-glucosidase enzyme activities) properties as well as their storage stability over a 90-day storage period. The functional orange juice exhibited an improved physicochemical, antioxidant, antidiabetic and shelf life properties based on the respective protein concentrations used over the 90-day study period while the sample with the lowest proportion (0.6%) of functional ingredient had the highest sensory acceptability. Hence, the study concluded that Kersting's groundnut proteins could find useful applications in the formulation of functional orange juice.

Spectroscopic studies on the antioxidant activity of ellagic acid

Ellagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 μg/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), α-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH• scavenging, ABTS+ scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that EA can be used in the pharmacological, food industry and medicine because of these properties.

Spectroscopic studies on the antioxidant activity of p-coumaric acid

p-coumaric acid (4-hydroxycinnamic acid), a phenolic acid, is a hydroxyl derivative of cinnamic acid. It decreases low density lipoprotein (LDL) peroxidation and reduces the risk of stomach cancer. In vitro radical scavenging and antioxidant capacity of p-coumaric acid were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe(2+)) chelating activity and ferric ions (Fe(3+)) reducing ability. p-Coumaric acid inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45μg/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and ascorbic acid displayed 66.8%, 69.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, p-coumaric acid had an effective DPPH scavenging, ABTS(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that p-coumaric acid can be used in the pharmacological and food industry because of these properties.