Reactions of hydroxyl radical with bergenin, a natural poly phenol studied by pulse radiolysis

Exploring the underlying pharmacological, immunomodulatory, and anti-inflammatory mechanisms of phytochemicals against wounds: a molecular insight

BACKGROUND

Numerous cellular, humoral, and molecular processes are involved in the intricate process of wound healing.

PHARMACOLOGICAL RELEVANCE

Numerous bioactive substances, such as ß-sitosterol, tannic acid, gallic acid, protocatechuic acid, quercetin, ellagic acid, and pyrogallol, along with their pharmacokinetics and bioavailability, have been reviewed. These phytochemicals work together to promote angiogenesis, granulation, collagen synthesis, oxidative balance, extracellular matrix (ECM) formation, cell migration, proliferation, differentiation, and re-epithelialization during wound healing.

FINDINGS AND NOVELTY

To improve wound contraction, this review delves into how the application of each bioactive molecule mediates with the inflammatory, proliferative, and remodeling phases of wound healing to speed up the process. This review also reveals the underlying mechanisms of the phytochemicals against different stages of wound healing along with the differentiation of the in vitro evidence from the in vivo evidence There is growing interest in phytochemicals, or plant-derived compounds, due their potential health benefits. This calls for more scientific analysis and mechanistic research. The various pathways that these phytochemicals control/modulate to improve skin regeneration and wound healing are also briefly reviewed. The current review also elaborates the immunomodulatory modes of action of different phytochemicals during wound repair.

Suppression of the phenolic SOA formation in the presence of electrolytic inorganic seed

Phenolic compounds are largely attributed to wildfire gases and rapidly react with atmospheric oxidants to form persistent phenoxy free radicals, which influence atmospheric chemistry and secondary organic aerosol (SOA) formation. In this study, phenol or o-cresol was photochemically oxidized under various conditions (NO_x levels, humidity, and seed conditions) in an outdoor photochemical reactor. Unexpectedly, SOA growth of both phenols was suppressed in the presence of salted aqueous aerosol compared to non-seed SOA. This discovery is different from the typical SOA formation of aromatic or biogenic hydrocarbons, which show noticeably higher SOA yields via organic aqueous reactions. Phenol, o-cresol, and their phenolic products (e.g., catechols) are absorbed in aqueous aerosol and form phenoxy radicals via heterogeneous reactions under sunlight. The resulting phenoxy radicals are redistributed between the gas and particle phases. Gaseous phenoxy radicals quickly react with ozone to form phenyl peroxide radicals and regenerated through a NO_x cycle to retard phenol oxidation and SOA formation. The explicit oxidation mechanisms of phenol or o-cresol in the absence of aqueous phase were derived including the Master Chemical Mechanism (MCM v3.3.1) and the path for peroxy radical adducts originating from the addition of an OH radical to phenols to form low volatility products (e.g., multi-hydroxy aromatics). The resulting gas mechanisms of phenol or o-cresol were, then, applied to the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model to predict SOA formation via multiphase partitioning of organics and aerosol-phase oligomerization. The model well simulated chamber-generated phenolic SOA in absence of wet-inorganic seed, but significantly overestimated SOA mass in presence of wet seed. This study suggests that heterogeneous chemistry to form phenoxy radicals needs to be included to improve SOA prediction from phenols. The suppression of atmospheric oxidation due to phenoxy radicals in wet inorganic aerosol can explain the low SOA formation during wildfire episodes.

Elucidation of reactive oxygen species scavenging pathways of norbergenin utilizing DFT approaches

Bergenin is a polyphenolic compound that contains isocoumarin skeletal derived from C-glycosylated 4-O-methylgallic acid. The biological activities of this compound and its derivatives are quite diverse. Recent studies reveal neuroprotective effects in vitro and in vivo in Alzheimer's. Norbergenin is a demethylated form of bergenin, known for better antioxidant capacity and associated with neuroprotective properties through oxidative stress inhibition. This study focused on investigating the scavenging mechanism of norbergenin with the ^•OH, ^•OOH, and O 2 ∙ - as a radical model under physiological and lipid environments. The thermodynamic and kinetic parameters of the hydrogen transfer (HT), single electron transfer (SET), sequential proton lost-electron transfer (SPLET) and radical adduct formation (RAF) mechanisms were determined theoretically by the density functional theory (DFT) at M06-2X/6-311 + + G(d,p) level of theory. Based on the computational results, this compound has proved as an excellent ^•OOH and ^•OH scavenger under physiological conditions better than Trolox and vitamin C, whereas its radical demonstrated as an efficient O 2 ∙ - scavenger.

Vasorelaxant and Antihypertensive Effects of Bergenin on Isolated Rat Aorta and High Salt-Induced Hypertensive Rats

Bergenin is a phenolic glycoside that has been reported to be present in some medicinal plants which are traditionally used for their antihypertensive actions. So, bergenin was investigated for antihypertensive and vasorelaxant experiments in a rat model. Bergenin produced a significant fall in the mean arterial pressure (MAP) of rats. To explore the involvement of NO and muscarinic receptors, rats were pretreated with L-NAME and atropine in-vivo. The L-NAME did not change significantly the effect of bergenin on MAP excluding the involvement of NO. Unlike the L-NAME, atropine pretreatment reduced the effect of bergenin on MAP, indicating the role of muscarinic receptors. In in-vitro study, the bergenin produced endothelium-dependent (at lower concentrations) and independent (at higher concentrations) vasorelaxation, which was attenuated significantly in the presence of atropine and indomethacin but not with L-NAME. While a partial response was observed against K⁺-induced contractions. This was further confirmed when bergenin partly shifted the CaCl₂-CRCs toward right. Bergenin also suppressed the PE peak formation, indicating the antagonist effect against the release of Ca²⁺. Moreover, the bergenin-induced vasorelaxant response was not markedly attenuated with TEA, while significantly ablated with 4-AP and BaCl₂. In conclusion, the antihypertensive effects of bergenin are due to Ca²⁺ channel blockade, K⁺ channels activation, and muscarinic receptor-linked vasodilation.

Bergenin from Bergenia Species Produces a Protective Response against Myocardial Infarction in Rats

Bergenin is a phenolic glycoside that has been reported to occur naturally in several plant species, reported as a cardioprotective. However, bergenin, one of the important phytochemicals in these plants, is still not reported as a cardioprotective. The present study was designed to investigate the cardioprotective effects of bergenin on isoproterenol-induced myocardial infarction in rats. Bergenin and atenolol were administered through intraperitoneal (i.p.) injection to Sprague Dawley (SD) rats in separate experiments for five (5) days. At the end of this period, rats were administered isoproterenol (80 mg/kg s.c.) to induce myocardial injury. After induction, rats were anaesthetized to record lead II ECG, then sacrificed, blood was collected to analyze cardiac marker enzymes, and a histopathological study of the heart tissues was also performed. Pretreatment with bergenin showed a significant decrease in ST-segment elevation, deep Q-wave, infarct size, and also normalized cardiac marker enzymes (cTnI, CPK, CK-MB, LDH, ALT, and AST), particularly at 3 mg/kg, as compared to isoproterenol treated group. Our findings revealed, for the first time, the use of glycoside bergenin as a potential cardioprotective agent against the isoproterenol-induced MI in rats.

Diversity, pharmacology and synthesis of bergenin and its derivatives: potential materials for therapeutic usages

Bergenin, a natural secondary metabolite, has been isolated from different parts of a number of plants. It is one of active ingredients in herbal and Ayurvedic formulations. It exhibits antiviral, antifungal, antitussive, antiplasmodial, antiinflammatory, antihepatotoxic, antiarrhythmic, antitumor, antiulcerogenic, antidiabetic and wound healing properties. It has been analyzed and estimated in different plant extracts, blood and drug samples using chromatographic techniques, and pharmacokinetic studies have been made. Several bergenin derivatives were isolated and/or synthesized and were found to possess pharmacological activities. Total synthesis of bergenin and its derivatives were reported. This review article covers literature on bergenin and its derivatives until 2013. Ethnomedicinal value of bergenin containing plant materials is also highlighted. This comprehensive review provides information on the potentiality of bergenin and its derivatives for therapeutic usages.

Assessing the photochemical transformation pathways of acetaminophen relevant to surface waters: transformation kinetics, intermediates, and modelling

This work shows that the main photochemical pathways of acetaminophen (APAP) transformation in surface waters would be direct photolysis (with quantum yield of (4.57 ± 0.17)⋅10(-2)), reaction with CO3(-·) (most significant at pH > 7, with second-order rate constant of (3.8 ± 1.1)⋅10(8) M(-1) s(-1)) and possibly, for dissolved organic carbon higher than 5 mg C L(-1), reaction with the triplet states of chromophoric dissolved organic matter ((3)CDOM*). The modelled photochemical half-life time of APAP in environmental waters would range from days to few weeks in summertime, which suggests that the importance of phototransformation might be comparable to biodegradation. APAP transformation by the main photochemical pathways yields hydroxylated derivatives, ring-opening compounds as well as dimers and trimers (at elevated concentration levels). In the case of (3)CDOM* (for which the triplet state of anthraquinone-2-sulphonate was used as proxy), ring rearrangement is also hypothesised. Photochemistry would produce different transformation products (TPs) of APAP than microbial biodegradation or human metabolism, thus the relevant TPs might be used as markers of APAP photochemical reaction pathways in environmental waters.

Oxidation reactions of 1- and 2-naphthols: an experimental and theoretical study

The transients formed during the reactions of oxidizing radicals with 1-naphthol (1) and 2-naphthol (2) in aqueous medium have been investigated by pulse radiolysis with detection by absorption spectroscopy and density functional theory (DFT) calculations. The transient spectra formed on hydroxyl radical ((•)OH) reactions of 1 and 2 exhibited λ(max) at 340 and 350 nm at neutral pH. The rate constants of the (•)OH reactions of 1 (2) were determined from build-up kinetics at λ(max) of the transients as (9.63 ± 0.04) × 10(9) M(-1) s(-1) ((7.31 ± 0.11) × 10(9) M(-1) s(-1)). DFT calculations using the B3LYP/6-31+G(d,p) method have been performed to locate favorable reaction sites in both 1 and 2 and identification of the pertinent transients responsible for experimental results. Calculations demonstrated that (•)OH additions can occur mostly at C1 and C4 positions of 1, and at C1 and C8 positions of 2. Among several isomeric (•)OH adducts possible, the C1 adduct was found to be energetically most stable both in 1 and 2. Time-dependent density functional theory (TDDFT) calculations in the solution phase has shown that the experimental spectrum of 1 was mainly attributed by 1a4 (kinetically driven (•)OH-adduct) formed via the addition of (•)OH at the C4 position which was 0.73 kcal/mol endergonic compared to 1a1 (thermodynamic (•)OH adduct), whereas 2a1 (thermodynamic/kinetic (•)OH-adduct) was mainly responsible for the experimental spectrum of 2. Naphthoxyl radicals of 1 and 2 have been predicted as the transient formed in the reaction of (•)OH at basic pH. In addition, the same transient species resulted from the reactions of oxide radical ion (O(•-)) at pH ≈ 13 and azide radical (N3(•)) at pH 7 with 1 and 2. Further, UV photolysis of aqueous solutions of 1 and 2 containing H2O2 (UV/H2O2) were used for the (•)OH induced oxidation product formations up on 60% degradations of 1 and 2; profiling of the oxidation products were performed by using an ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) method. According to the UPLC-Q-TOF-MS analyses, the preliminary oxidation products are limited to dihydroxy naphthalenes and naphthoquinones with N2-saturation, while some additional products (mainly isomeric monohydroxy-naphthoquinones) have been observed in the degradations of 1 and 2 in the presence of O2. We postulate that dihydroxy naphthalenes are derived explicitly from the most favorable (•)OH-adducts speculated (preference is in terms of the kinetic/thermodynamic dominancy of transients) by using theoretical calculations which in turn substantiate the proposed reaction mechanisms. The observations of (•)OH-adducts for an aromatic phenol (herein for both 1 and 2 at pH 7) rather than phenoxyl type radical in the pulse radiolysis experiments is a distinct and unique illustration. The present study provides a meaningful basis for the early stages associated with the (•)OH initiated advanced oxidation processes of 1- and 2-naphthols.

LC-MS/MS determination and pharmacokinetic study of bergenin, the main bioactive component of Bergenia purpurascens after oral administration in rats

Bergenin, a C-glucoside of 4-O-methyl gallic acid from Bergenia purpurascens, is a naturally antitussive and expectorant agent. A rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the determination of the active component-bergenin, in rat plasma after oral administration of aqueous B. purpurascens extract. The plasma samples were pretreated by protein precipitation with acetonitrile and chromatographic separation was achieved on a Diamonsil® C18 column (150 mm×4.6 mm, 5 μm) with isocratic elution using a mobile phase consisting of water-methanol (30:70, v/v) at a flow rate of 0.6 mL/min. The detection was accomplished by a triple-quadrupole tandem mass spectrometer in multiple-reaction monitoring (MRM) scanning via an electrospray ionization (ESI) source operating in the negative mode. The optimized mass transition ion-pairs (m/z) for quantitation were 327.3/192.0 for bergenin, and 431.1/311.1 for IS. The time for each analysis run was only 3.5 min between injections. The calibration curve exhibited good linearity (r2>0.99) over a range of 1.00-2000 ng/mL for bergenin. The lower limit of quantitation (LLOQ) was 1.00 ng/mL. The intra- and inter-day precisions were no more than 11.8%, and relative errors (RE) were within the range of 0.0-4.4%. The validated method was successfully applied to investigate the pharmacokinetics of bergenin after oral administration of B. purpurascens extract in rats.

Phytochemical, antioxidant and anti-α-glucosidase activity evaluations of Bergenia cordifolia

The antioxidant, anti-α-glucosidase and anticholinesterase activity of the leaves and rhizomatous extract of Bergenia cordifolia were investigated. The rhizomes extract that showed a higher degree of 1,1-diphenyl-2-picrylhydrazyl radical scavenging and anti-α-glucosidase activity than reference compounds (rutin and acarbose respectively) were subjected to phytochemical analysis. The study revealed that previously unknown minor constituents from the plant, (+)-catechin 3-O-gallate, (+)-catechin 3,5-di-O-gallate and 1,2,4,6-tetra-O-galloyl-β-D-glucopyranoside, were the radical scavenging and anti-α-glucosidase principles. These compounds as well as the crude extracts were weak acetylcholienesterase inhibitors, suggesting a higher degree of selectivity against α-glucosidase enzyme. In comparison with the minor constituents, the previously known major constituents of the plant, bergenin and arbutin, were poor radical scavengers and enzyme inhibitors.