Imidacloprid effects on acetylcholinesterase and nicotinic acetylcholine receptor in Apis mellifera. Experimental and molecular modeling approaches.

Although the neonicotinoid insecticides have good selectivity towards insects rather than vertebrates, they have severe effects on honeybee production and pollination activities. Therefore, the effects of imidacloprid (IMI), the most used neonicotinoid, on the two main bioreceptors, acetylcholinesterase (AChE) and nicotinic acetylcholine receptor alpha subunit (nAChRα1) of honeybees were examined to identify their roles in honeybee toxicity and possible binding sites which assist in selecting and designing neonicotinoids. In vivo, IMI showed a high inhibitory effect on AChE (IC50 5.63 mg/L); however, the effect was much lower in vitro experiment (IC50 719 mg/L). This result induced us to examine the IMI effect on AChE gene expression which revealed that the AChE-2 gene expression was severely affected by IMI explaining the observed high enzyme inhibition. In addition, although toxicity increased by increasing exposure to IMI (LC50 2.9 mg/L after 4h and 0.75 mg/L after 48h), AChE was not elevated (IC50 5.63 and 5.52 mg/L respectively). Besides, Despite resuming most enzyme activity (77% during 2 h and 84.14% after 4 h), a high mortality level was observed with LC50 2.9 mg/L. These results reinforced that the observed high toxicity is a multifactor process. Accordingly, Molecular modeling and docking of IMI into honeybee AChE and nAChRα1were also performed to examine their possible interactions and identify the important binding sites. Results models indicated that the first two binding sites in AChE were found in the esteratic subunit in the active site explaining the observed in vitro inhibition. In nAChRα1, four of the highest five free energy binding sites are located in the large TM3-TM4 loop and one in the extracellular loops. Consequently, the present work revealed that IMI toxicity is attributed to various factors including direct interaction with both AChE and nAChRα1 as well as downregulating AChE-2 gene expression.

Enhancing the Stability of Strawberry Anthocyanins Complexed to ß-Cyclodextrin and Starch toward Heat, Oxidation, and Irradiation.

The instability of anthocyanins limits their application in food supplementation and in the food industry. Stabilities of strawberry anthocyanins (AN) were improved by complexation with both ß-CD and starch against heat, H2O2, light, and UV irradiation. The stability of AN against H2O2 (2.21 mM) dropped (<20%) in 6 h but was enhanced in ß-CD (49.32%) and starch (96.84%) complexes. Under light conditions, AN in the solid and solution (3.88 g/100 mL) forms degraded to 36.49 and 11.11%, while ß-CD and starch complexes displayed stabilities of 98.20 and 91.76%, respectively, after 60 days. Under UV irradiation, AN showed similar instability where both AN forms expressed stabilities of 36.75 and 66.18%, respectively, after 168 h, while ß-CD and starch complexes exhibited 51.13 and 40.10%, respectively. LC-MS-ESI showed that photoirradiation of both destroyed the full conjugation of the flavylium ring of the major components, pelargonidin and cyanidin hexoses; the mechanism was proposed. Docking binding models of major AN components in ß-CD were obtained.

Involvement of PI3K/HIF-1α/c-MYC/iNOS Pathway in the Anticancer Effect of Suaeda vermiculata in Rats.

Suaeda vermiculata Forssk. ex JF Gmel. (SV), a traditional known plant, has shown in vitro cytotoxic activity against HepG2 and HepG-2/ADR (doxorubicin-resistant cells) liver cell carcinoma cell lines, as well as hepatoprotection against paracetamol and carbon tetrachloride (CCl4)-induced liver injury. The current study evaluated the protective effect of SV, administered against N-diethylnitrosamine (NDEA)-induced HCC in rats. The possible modulatory effect of SV on the PI3K/HIF-1α/c-MYC/iNOS pathway was investigated. Sixty male adult albino rats (200 ± 10 g) were equally classified into five groups. Group I served as a control; Group 2 (SV control group) received SV (p.o., 200 mg/kg body weight); Group 3 (NDEA-administered rats) received freshly prepared NDEA solution (100 mg/L); and Groups 4 and 5 received simultaneously, for 16 weeks, NDEA + SV extract (100 and 200 mg/kg, orally). NDEA-treated rats displayed significant increases in serum levels of AFP, CEA, PI3K, malondialdehyde (MDA), epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGFR), with increased liver tissue protein expression of fibrinogen concomitant and significantly decreased concentrations of antioxidant parameters (catalase (CAT), superoxide dismutase (SOD), and reduced glutathione (GSH)) in comparison to normal rats. On the flip side, AFP, CEA, PI3K, MDA, EGFR, and VEGFR serum levels were significantly reduced in rats that received NDEA with SV, both at low (SV LD) and high (SV HD) doses, accompanied by significant improvements in antioxidant parameters compared to the NDEA-treated group. Conclusions: SV possesses a significant hepatoprotective effect against NDEA-induced HCC via inhibiting the PI3K/HIF-1α/c-MYC/iNOS pathway, suggesting that SV could be a promising hepatocellular carcinoma treatment.

Evaluation of Cisplatin-Induced Acute Renal Failure Amelioration Using Fondaparinux and Alteplase.

Acute renal failure (ARF) is a deleterious condition with increased mortality or healthcare costs or dialysis-dependent end-stage renal disease. The study aims to compare prophylaxis with fondaparinux (Fund) vs. treatment with alteplase (Alt) in ameliorating cisplatin (Cis)-induced ARF. Sixty male mice were equally divided randomly into six groups of control, Cis, Alt, and Cis + Alt groups receiving normal saline for 10 days. All four groups except for the control received Cis (30 mg/kg, i.p.) on day 7, and 6 h later, both the Alt groups received Alt (0.9 mg/kg, i.v.). The animal groups Fund and Fund + Cis received Fund (5 mg/kg, i.p.) for 10 days, and the Fund + Cis group on day 7 received Cis. All the animal groups were euthanized 72 h after the Cis dose. The Fund + Cis group showed significantly increased expression levels of platelet count, retinoid X receptor alpha (RXR-α) and phosphorylated Akt (p-Akt) in addition to decreased levels of urea, blood urea nitrogen (BUN), uric acid, white blood cells (WBCs), red blood cells (RBCs), relative kidney body weight, kidney injury score, glucose, prothrombin (PT), A Disintegrin And Metalloproteinases-10 (ADAM10), extracellular matrix deposition, protease-activated receptor 2 (PAR-2), and fibrinogen expression when compared to the Cis-only group. Meanwhile, the Cis + Alt group showed increased caspase-3 expression in addition to decreased levels of urea, BUN, uric acid, WBCs, RBCs, glucose, platelet count and PT expression with a marked decrease in PAR-2 protein expression compared to the Cis group. The creatinine levels for both the Fund + Cis and Cis + Alt groups were found to be comparable to those of the Cis-only group. The results demonstrate that the coagulation system's activation through the stimulation of PAR-2 and fibrinogen due to Cis-induced ADAM10 protein expression mediated the apoptotic pathway, as indicated by caspase-3 expression through the p-Akt pathway. This is normally accompanied by the loss of RXR-α distal and proximal tubules as lipid droplets. When the animals were pre-treated with the anticoagulant, Fund, the previous deleterious effect was halted while the fibrinolytic agent, Alt, most of the time failed to treat Cis-induced toxicity.

Topical Eucalyptol Ointment Accelerates Wound Healing and Exerts Antioxidant and Anti-Inflammatory Effects in Rats' Skin Burn Model.

Eucalyptol is a major volatile constituent among well-known wound healing medicinal plants. The current study evaluated eucalyptol wound healing activity in the rat's third-degree skin-burn model. The parameters, i.e., skin-healing, oxidative/antioxidant markers, pro-/anti-inflammatory markers, were evaluated after 1- and 2-weeks of treatment regimens with 5% eucalyptol ointment. Eucalyptol-loaded ointment base of 5% w/w strength was formulated using fusion method and physically evaluated for consistency, stability, and homogeneity. A 25-rats were divided randomly into intact, negative control (untreated), silver sulfadiazine (SS, positive control), 1-week, and 2-weeks treated eucalyptol groups. Using an aluminum cylinder (120℃, 10 second duration), 3rd-degree skin burns were created on the rat's dorsum. Skin biopsies were collected at the end of the experiment for biochemical and histological investigations. Compared to the negative group; time-dependent wound size reduction and decreased edema were observed in eucalyptol-treated animals. Histopathological examinations demonstrated epidermis integrity, decreased neutrophil, and increased capillaries number in the 2-weeks and SS groups, compared to the negative and 1-week treated eucalyptol groups. Compared to the untreated animals, the 1- and 2-weeks eucalyptol treated groups' demonstrated significantly increased antioxidant superoxide dismutase (SOD, p=0.002 and p=0.003, respectively) and reduced lipid peroxide (LP, p=0.005 and p=0.0006, respectively). However, a significant increment of catalase (CAT, p=0.0009) was found only in the 2-weeks of eucalyptol group at a level of 2.42 ± 0.39 ng/g compared to 1.14 ± 0.04 ng/g in the untreated animals. Also, significant reductions in the cytokines, IL-1b, IL-6, and TNF-α (p < 0.05); and increase in the pro-angiogenic marker, IL-10, were detected in the 2-weeks (p=0.001) and SS (p=0.002) treated animals compared to the negative and 1-week eucalyptol treated groups. The study concluded that eucalyptol induced significant duration-based wound healing properties attributed to its antioxidant and anti-inflammatory effects.

Cinnamaldehyde-Based Self-Nanoemulsion (CA-SNEDDS) Accelerates Wound Healing and Exerts Antimicrobial, Antioxidant, and Anti-Inflammatory Effects in Rats' Skin Burn Model.

Cinnamaldehyde, the main phytoconstituent of the cinnamon oil, has been reported for its potential wound healing activity, associated to its antimicrobial and anti-inflammatory effects. In this study, we are reporting on the cinnamaldehyde-based self-nanoemulsifying drug delivery system (CA-SNEDDS), which was prepared and evaluated for its antimicrobial, antioxidant, anti-inflammatory, and wound healing potential using the rat third-degree skin injury model. The parameters, i.e., skin healing, proinflammatory, and oxidative/antioxidant markers, were evaluated after 3 weeks of treatment regimens with CA-SNEDDS. Twenty rats were divided randomly into negative control (untreated), SNEDDS control, silver sulfadiazine cream positive control (SS), and CA-SNEDDS groups. An aluminum cylinder (120 °C, 10-s duration) was used to induce 3rd-degree skin burns (1-inch square diameter each) on the rat's dorsum. At the end of the experiment, skin biopsies were collected for biochemical analysis. The significantly reduced wound size in CA-SNEDDS compared to the negative group was observed. CA-SNEDDS-treated and SS-treated groups demonstrated significantly increased antioxidant biomarkers, i.e., superoxide dismutase (SOD) and catalase (CAT), and a significant reduction in the inflammatory marker, i.e., NAP-3, compared to the negative group. Compared to SNEDDS, CA-SNEDDS exhibited a substantial antimicrobial activity against all the tested organisms at the given dosage of 20 µL/disc. Among all the tested microorganisms, MRSA and S. typhimurium were the most susceptible bacteria, with an inhibition zone diameter (IZD) of 17.0 ± 0.3 mm and 19.0 ± 0.9 mm, respectively. CA-SNEDDS also exhibited strong antifungal activity against C. albicans and A. niger, with IZD of 35.0 ± 0.5 mm and 34.0 ± 0.5 mm, respectively. MIC and MBC of CA-SNEDDS for the tested bacteria ranged from 3.125 to 6.25 µL/mL and 6.25 to 12.5 µL/mL, respectively, while the MIC and MBC for C. albicans and A. niger were 1.56 µL/mL and 3.125 µL/mL, respectively. The MBIC and MBEC of CA-SNEDDS were also very significant for the tested bacteria and ranged from 6.25 to 12.5 µL/mL and 12.5 to 25.0 µL/mL, respectively, while the MBIC and MBEC for C. albicans and A. niger were 3.125 µL/mL and 6.25 µL/mL, respectively. Thus, the results indicated that CA-SNEDDS exhibited significant wound healing properties, which appeared to be attributed to the formulation's antimicrobial, antioxidant, and anti-inflammatory effects.

Bio-Evaluation of the Wound Healing Activity of Artemisia judaica L. as Part of the Plant's Use in Traditional Medicine; Phytochemical, Antioxidant, Anti-Inflammatory, and Antibiofilm Properties of the Plant's Essential Oils.

Artemisia judaica (ArJ) is a Mediterranean aromatic plant used traditionally to treat gastrointestinal ailments, skin diseases, atherosclerosis, and as an immuno-stimulant. This study describes ArJ essential oil constituents and investigates their wound healing activity. The in vitro antioxidant and antibiofilm activities of ArJ essential oil were investigated. The in vivo pro/anti-inflammatory and oxidative/antioxidant markers were compared with standard silver sulfadiazine (SS) in a second-degree skin burn experimental rat model. The gas chromatography-equipped flame ionization detector (GC-FID) analysis of ArJ essential oil revealed the major classes of compounds as oxygenated monoterpenes (>57%) and cinnamic acid derivatives (18.03%). The antimicrobial tests of ArJ essential oil revealed that Bacillus cereus, Candida albicans, and Aspergillus niger were the most susceptible test organisms. Two second-degree burns (each 1 inch square in diameter) were created on the dorsum of rats using an aluminum cylinder heated to 120 °C for 10 s. The wounds were treated either with ArJ or SS ointments for 21 days, while the negative control remained untreated, and biopsies were obtained for histological and biochemical analysis. The ArJ group demonstrated a significant increase in antioxidant superoxide dismutase (SOD) and catalase (CAT) enzymatic activities, while lipid peroxide (LP) levels remained insignificant compared to the negative control group. Additionally, ArJ and SS groups demonstrated a significant decrease in inflammatory levels of tumor necrosis factor α (TNF-α) compared to the negative group, while interleukin 1 beta (IL-1b) and IL-6 were comparable to the negative group. At the same time, anti-inflammatory IL-10 and transforming growth factor beta 1 (TGF-b1) markers increased significantly in the ArJ group compared to the negative control. The ArJ results demonstrated potent wound healing effects, comparable to SS, attributable to antioxidant and anti-inflammatory effects as well as a high proportion of oxygenated monoterpenes and cinnamate derivatives.

SAR and QSAR of COVID-19 Main Protease-Inhibitor Interactions of Recently X-ray Crystalized Complexes.

COVID-19 is still widespread worldwide and up to now there is no established antiviral able to control the disease. Main protease is responsible for the viral replication and transcription; thus, its inhibition is a promising route to control virus proliferation. The present study aims to examine detail interactions between main protease and recently reported ninety-seven inhibitors with available X-ray crystallography to define factors enhance inhibition activity; thirty-two of most potent inhibitors were examined to identify sites and types of interaction. The study showed formation of covalent bond, H-bond and hydrophobic interaction with key residues in the active side. Covalent bond is observed in seventeen complexes, all of them by attack of the 145Cys thiol group on Michael acceptor, aldehyde or its hydrate, α-ketoamide, double bond or acetamide methyl group; the latter type requires H-bonding between acetamide carbonyl oxygen and at least one of 143Gly, 144Ser or 145Cys. Potent inhibitors, disulfiram and ebselen docked in the same binding site. Accordingly, factors identify inhibition include forming covalent bond and existing terminal hydrophobic groups and amidic or peptidomimetic structure. Binding affinity was found correlated with topological diameter up to 24 bond, molecular size, branching, polar surface area up to 199 Å2 and hydrophilicity. Supplementary Information: The online version contains supplementary material available at 10.1007/s40011-021-01338-8.

Neuroprotective Effect of Clobenpropit against Lipopolysaccharide-Induced Cognitive Deficits via Attenuating Neuroinflammation and Enhancing Mitochondrial Functions in Mice.

Clobenpropit (CLO), an antagonist on histamine H3 receptors (HH3R), has been shown to protect NMDA-induced neuronal necrosis in cortical neuronal cell culture from rats. In this work, we explored its potential on lipopolysaccharide (LPS)-induced memory deficits, neuroinflammation, and mitochondrial dysfunction in mice. CLO (1 and 3 mg/kg, p.o.) was treated continually for 30 days, and neurotoxicity was induced by four doses of LPS (250 µg/kg, i.p.). The radial arm maze (RAM) was used to access memory behaviors. After the REM test, brain tissue was collected from each mouse to estimate pro-inflammatory cytokines (TNFα and IL6), anti-inflammatory cytokines (TGF-ß1 and IL-10), cyclooxygenase-2 (COX 2), and mitochondrial respiratory chain complex (MRCC- I, II and IV) enzymes. CLO treatment reversed the LPS-induced behavioral deficits by a significant reduction in time taken to consume all five bites (TTB), working memory error (WME), and reference memory error (REM) in the REM test. Regarding neuroinflammation, it attenuated the release of COX, TNF-α, and IL-6, and augmented TGF-ß1 and IL-10 levels in the brain. Reversal of LPS-induced brain MRCC (I, II, and IV) levels also resulted with CLO treatment. From these findings, CLO promises neuroprotection against LPS-induced cognitive deficits by ameliorating neuroinflammation and restoring the MRCC enzymes in mice.

Comparative Phytochemical Profile and Biological Activity of Four Major Medicinal Halophytes from Qassim Flora.

Four halophytic plants, Lycium shawii, Anabasis articulata, Rumex vesicarius, and Zilla spinosa, growing in the central Qassim area, Saudi Arabia, were phytochemically and biologically investigated. Their hydroalcoholic extracts' UPLC-ESIQ-TOF analyses demonstrated the presence of 44 compounds of phenolic acids, flavonoids, saponins, carbohydrates, and fatty acids chemical classes. Among all the plants' extracts, L. shawii showed the highest quantities of total phenolics, and flavonoids contents (52.72 and 13.01 mg/gm of the gallic acid and quercetin equivalents, respectively), along with the antioxidant activity in the TAA (total antioxidant activity), FRAP (ferric reducing antioxidant power), and DPPH-SA (2,2-diphenyl-1-picryl-hydrazyl-scavenging activity) assays with 25.6, 56.68, and 19.76 mg/gm, respectively, as Trolox equivalents. The hydroalcoholic extract of the L. shawii also demonstrated the best chelating activity at 21.84 mg/gm EDTA equivalents. Among all the four halophytes, the hydroalcoholic extract of L. shawii exhibited the highest antiproliferative activity against MCF7 and K562 cell lines with IC50 values at 194.5 µg/mL and 464.9 µg/mL, respectively. The hydroalcoholic extract of A. articulata demonstrated better cytotoxic activity amongst all the tested plants' extracts against the human pancreatic cancer cell lines (PANC1) with an IC50 value of 998.5 µg/mL. The L. shawii induced apoptosis in the MCF7 cell lines, and the percentage of the necrotic cells changed to 28.1% and 36.5% for the IC50 and double-IC50 values at 22.9% compared with the untreated groups. The hydroalcoholic extract of L. shawii showed substantial antibacterial activity against Bacillus cereus ATCC 10876 with a MIC value of 12.5 mg/mL. By contrast, the A. articulata and Z. spinosa exhibited antifungal activities against Aspergillus niger ATCC 6275 with MIC values at 12.5 and 50 mg/mL, respectively. These findings suggested that the L. shawii is a potential halophyte with remarkable biological properties, attributed to its contents of phenolics and flavonoid classes of compounds in its extract.

Bioavailability and antioxidant potentials of fresh and pasteurized kiwi juice before and after in vitro gastrointestinal digestion.

The aim of the present work was to find the changes in the chemical composition, chemical structure and antioxidant activity of bioactive nutrients of kiwi juices upon pasteurization and in vitro gastrointestinal digestion. Results showed that fresh kiwi juice (FKJ) contains total phenols, 162 mg GAE/mL, total flavonoids 1.44 mg QE/mL, ascorbic acid 4.5 mg/mL and fiber 60%; these contents were marginally affected by pasteurization (PKJ) to be 122, 1.02, 2.6 and 47 respectively. On the other hand, gastrointestinal digestion severely lowered total phenols, total flavonoids and ascorbic acid in digested fresh kiwi juice (DFKJ) to 49 mg GAE/mL,0.16 mg GE/mL and 2.2 mg/mL, and in digested pasteurized kiwi juice (DPKJ) to 42, 0.07 and 1.2 respectively; however fiber contents increased upon digestion as a result of decreasing other nutrients. The antioxidant and reducing power activities followed the same order of decreasing total phenols, total flavonoids and ascorbic acid contents i.e. FKJ > PKJ > DFKJ > DPKJ. The major flavonoid found was apigenin in the form of various glycosides differ in the number (1-3) and position of the sugar units. Pasteurization showed minor effects on the chemical composition of fresh juice while digestion, as a result of gastrointestinal enzymes had more effect but mainly on the number and position of the sugar units rather than affecting the flavonoid moiety which preserve the main nutritive values.

Energetic and electronic computation of the two-hydrogen atom donation process in catecholic and non-catecholic anthocyanidins.

Antioxidant activity of anthocyanidins is greatly affected by the 3-hydroxyl group and/or a catecholic moiety. The two-hydrogen atom donation process is frequently used to explain the high antioxidant activity of polyphenolic compounds leading to the formation of stable diketones e.g. 1,2-quinones. Thermodynamic parameters, HOMO and spin density were computed to identify the favoured path, either through the 3-hydroxyl group or through the catecholic moiety in a series of catecholic and non-catecholic 3-oxy- (and deoxy)-anthocyanidins. DFT calculations showed that the donation process in non-catecholic anthocyanidins depended on the substituents on ring B. Anthocyanidins with 3',5'-diOMe groups showed donation through 3,4'-OH or, otherwise, through 3,5-OH groups. Catecholic 3-oxyanthocyanidins, on the other hand, showed donation through the 3,4'-OH path rather than the catecholic path (4',3'-path). The 3,4'-path was favoured by the formation of planar 3-radicals in the first step and the stabilization of 4'-radicals in the second step by H-bonding with the 3'-OH group.

Antiradical and reductant activities of anthocyanidins and anthocyanins, structure-activity relationship and synthesis.

Eight anthocyanidins, seven anthocyanins and two synthesized 4'-hydroxy flavyliums were examined as hydrogen donors to DPPH, ABTS and hydroxyl radicals, and as electron donors in the FRAP assay. Most compounds gave better activities than trolox and catechol. A structure-activity relationship (SAR) study showed that, in the absence of the 3-OH group, radicals of the 4, 5 or 7-OH groups can only be stabilized by resonance through pyrylium oxygen, while 3-OH group improved hydrogen atom donation because of the stabilization by anthocyanidin semiquinone-like resonance. Electron donation was also enhanced by the 3-OH group. Both anthocyanidins and their respective anthocyanins showed similar trends and close activities. Different types of sugar unit bonded to the 3-OH group or counter ion had minor effect on activities. The catechol structure improved both hydrogen and electron donation. Compounds lacking the catechol structure had a decreasing order of H-atom and electron donation (Mv>Pn>Pg>Ap>4'-OH-flavylium) consistent with the decreasing number of their hydroxyl and/or methoxy groups.

The role of various amino acids in enzymatic browning process in potato tubers, and identifying the browning products.

The effects of five structurally variant amino acids, glycine, valine, methionine, phenylalanine and cysteine were examined as inhibitors and/or stimulators of fresh-cut potato browning. The first four amino acids showed conflict effects; high concentrations (⩾ 100mM for glycine and ⩾ 1.0M for the other three amino acids) induced potato browning while lower concentrations reduced the browning process. Alternatively, increasing cysteine concentration consistently reduced the browning process due to reaction with quinone to give colorless adduct. In PPO assay, high concentrations (⩾ 1.11 mM) of the four amino acids developed more color than that of control samples. Visible spectra indicated a continuous condensation of quinone and glycine to give colored adducts absorbed at 610-630 nm which were separated and identified by LC-ESI-MS as catechol-diglycine adduct that undergoes polymerization with other glycine molecules to form peptide side chains. In lower concentrations, the less concentration the less developed color was observed.

Browning inhibition mechanisms by cysteine, ascorbic acid and citric acid, and identifying PPO-catechol-cysteine reaction products.

The titled compounds were examined as PPO inhibitors and antibrowning agents; their various mechanisms were investigated and discussed. All compounds reduced significantly both the browning process and PPO activity. Browning index gave strong correlation with PPO activity (r(2) = 0.96, n = 19) indicating that the browning process is mainly enzymatic. Ascorbic acid could reduce the formed quinone instantly to the original substrate (catechol) at high concentration (>1.5 %) while at lower concentrations acted as competitive inhibitor (KI = 0.256 ± 0.067 mM). Cysteine, at higher concentrations (≥1.0 %), reacted with the resulted quinone to give a colorless products while at the low concentrations, cysteine worked as competitive inhibitor (KI = 1.113 ± 0.176 mM). Citric acid acted only as PPO non-competitive inhibitor with KI = 2.074 ± 0.363 mM. The products of PPO-catechole-cysteine reaction could be separation and identification by LC-ESI-MS. Results indicated that the product of the enzymatic oxidation of catechol, quinone, undergoes two successive nucleophilic attacks by cysteine thiol group. Cysteine was condensed with the resulted mono and dithiocatechols to form peptide side chains.

Structural features, kinetics and SAR study of radical scavenging and antioxidant activities of phenolic and anilinic compounds.

BACKGROUND: Phenolic compounds are widely distributed in plant kingdom and constitute one of the most important classes of natural and synthetic antioxidants. In the present study fifty one natural and synthetic structurally variant phenolic, enolic and anilinic compounds were examined as antioxidants and radical scavengers against DPPH, hydroxyl and peroxyl radicals. The structural diversity of the used phenolic compounds includes monophenols with substituents frequently present in natural phenols e.g. alkyl, alkoxy, ester and carboxyl groups, besides many other electron donating and withdrawing groups, in addition to polyphenols with 1-3 hydroxyl groups and aminophenols. Some common groups e.g. alkyl, carboxyl, amino and second OH groups were incorporated in ortho, meta and para positions. RESULTS: SAR study indicates that the most important structural feature of phenolic compounds required to possess good antiradical and antioxidant activities is the presence of a second hydroxyl or an amino group in o- or p-position because of their strong electron donating effect in these positions and the formation of a stable quinone-like products upon two hydrogen-atom transfer process; otherwise, the presence of a number of alkoxy (in o or p-position) and /or alkyl groups (in o, m or p-position) should be present to stabilize the resulted phenoxyl radical and reach good activity. Anilines showed also similar structural feature requirements as phenols to achieve good activities, except o-diamines which gave low activity because of the high energy of the resulted 1,2-dimine product upon the 2H-transfer process. Enols with ene-1,2-diol structure undergo the same process and give good activity. Good correlations were obtained between DPPH inhibition and inhibition of both OH and peroxyl radicals. In addition, good correlations were obtained between DPPH inhibition and antioxidant activities in sunflower oil and liver homogenate systems. CONCLUSIONS: In conclusion, the structures of good anti radical and antioxidant phenols and anilines are defined. The obtained good correlations imply that measuring anti DPPH activity can be used as a simple predictive test for the anti hydroxyl and peroxyl radical, and antioxidant activities. Kinetic measurements showed that strong antioxidants with high activity have also high reaction rates indicating that factors stabilizing the phenoxyl radicals lower also the activation energy of the hydrogen transfer process.

Microwave-assisted synthesis and antimicrobial activities of flavonoid derivatives.

Eleven flavonoid derivatives were synthesised using a modified Baker-Venkataraman rearrangement, and subsequent microwave-assisted closure of the heterocyclic ring. All of the synthetic compounds displayed antifungal activity against Aspergillus niger and Fusarium oxysporium, and two of the synthetic flavonoid analogues exhibited significant activity against methicillin-resistant Staphylococcus aureus.