Structure-Activity Relationship of Flavonoids as Antioxidant and Pro-Oxidant Compounds

1,2,3-Triazole Hybrids Containing Isatins and Phenolic Moieties: Regioselective Synthesis and Molecular Docking Studies

The synthesis of hybrid molecules is one of the current strategies of drug discovery for the development of new lead compounds. The 1,2,3-triazole moiety represents an important building block in Medicinal Chemistry, extensively present in recent years. In this paper, we presented the design and the synthesis of new 1,2,3-triazole hybrids, containing both an isatine and a phenolic core. Firstly, the non-commercial azide and the alkyne synthons were prepared by different isatines and phenolic acids, respectively. Then, the highly regioselective synthesis of 1,4-disubstituted triazoles was obtained in excellent yields by a click chemistry approach, catalyzed by Cu(I). Finally, a molecular docking study was performed on the hybrid library, finding four different therapeutic targets. Among them, the most promising results were obtained on 5-lipoxygenase, an enzyme involved in the inflammatory processes.

Multistep Approach Points to Compounds Responsible for the Biological Activity and Safety of Hydrolates from Nine Lamiaceae Medicinal Plants on Human Skin Fibroblasts

As byproducts of essential oil distillation, hydrolates are used in natural cosmetics/biomedicine due to their beneficial skin effects. However, data on their safety with relevant biological targets, such as human skin cells, are scarce. Therefore, we have tested nine hydrolates from the Lamiaceae family with skin fibroblasts that are responsible for extracellular collagenous matrix builds. Thyme, oregano, and winter savoury hydrolates showed several times higher total phenolics, which correlated strongly with their radical scavenging and antioxidative capacity; there was no correlation between their viability profiles and the reducing sugar levels. No proteins/peptides were detected. All hydrolates appeared safe for prolonged skin exposure except for 10-fold diluted lavender, which showed cytotoxicity (~20%), as well as rosemary and lavandin (~10%) using viability, DNA synthesis, and cell count testing. Clary sage, oregano, lemon balm, and thyme hydrolates (10-fold diluted) increased fibroblast viability and/or proliferation by 10-30% compared with the control, while their viability remained unaffected by Mentha and winter savoury. In line with the STITCH database, increased viability could be attributed to thymol presence in oregano and thyme hydrolates in lemon balm, which is most likely attributable to neral and geranial. The proliferative effect of clary sage could be supported by alpha-terpineol, not linalool. The major volatile organic compounds (VOCs) associated with cytotoxic effects on fibroblasts were borneol, 1,8-cineole, and terpinene-4-ol. Further research with pure compounds is warranted to confirm the roles of VOCs in the observed effects that are relevant to cosmetic and wound healing aspects.

A versatile untargeted metabolomics-driven technology for rapid phytochemical profiling of stem barks of Zanthoxylum species with antioxidant and antimicrobial activities

Zanthoxylum species are credited with various uses in ethnomedicine due to their rich metabolite composition. In Kenya, these include management of cancer and microbial related ailments. However, there are limited reports showing how the bioactivity of Kenyan Zanthoxylum species is linked to their phytochemical profiles. This study therefore aimed at examining the chemical variation among five Zanthoxylum species found in Kenya (Z. chalybeum, Z. gilletii, Z. holtzianum, Z. paracanthum and Z. usambarense) using metabolomics approaches and the anti-oxidant and antimicrobial activities of these species. In a Folin–Ciocalteu test, the phenolic content of the stem bark extracts of these species were 73.083–145.272 mg TAE/g, while the alkaloids (in bromothymol blue chromogenic test) and flavonoids (in aluminium chloride test) were found to be 152.39–207.19 mg ME/g, and 109.416–186.413 mg CE/g, respectively. These extracts also exerted strong antioxidant activities in the 2,2-iphenyl-1-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power assays. In a broth dilution assay, the extract of the stem bark of Z. holtzianum ability showed the highest antimicrobial activity, followed by Z. chalybeum stem bark extract. The activities were positively correlated to both flavonoids and alkaloids concentrations, while the concentration of phenolics had weak negative correlation to antimicrobial activities. A chemometric analysis of the liquid-chromatography mass spectrometry profiles led to grouping of the species into three clusters. This study illustrates the variation in the bioactivity of Zanthoxylum species based on metabolite composition and justifies the wide usage of Zanthoxylum species in Kenyan traditional medicinal practices.

Graphical abstract

Biochemical Reactions and Their Biological Contributions in Honey

Honey is known for its content of biomolecules, such as enzymes. The enzymes of honey originate from bees, plant nectars, secretions or excretions of plant-sucking insects, or from microorganisms such as yeasts. Honey can be characterized by enzyme-catalyzed and non-enzymatic reactions. Notable examples of enzyme-catalyzed reactions are the production of hydrogen peroxide through glucose oxidase activity and the conversion of hydrogen peroxide to water and oxygen by catalase enzymes. Production of hydroxymethylfurfural (HMF) from glucose or fructose is an example of non-enzymatic reactions in honey.

Impact of the antioxidant quercetin on morphological integrity and follicular development in the in vitro culture of Bos indicus female ovarian fragments

We evaluated the effect of quercetin on the in vitro culture of bovine ovarian fragments in relation to morphology, development, and oxidative stress. Ovaries (n = 12) from Nelore heifers (n = 6) were used. Each pair of ovaries was divided into nine fragments, and one fragment from each animal was fixed in Bouin solution for 24 h (histology control) or frozen (- 80°C; control for oxidative stress). Other ovarian fragments (n = 8) were distributed into concentrations of 0, 10, 25, and 50 μg/mL of quercetin added to the culture medium for 5 or 10 d. Data were analyzed by chi-square test or ANOVA followed by Tukey's test (P < 0.05). Treatment with 25 μg/mL quercetin resulted in the highest proportion of total intact follicles for 5 (67.3%) and 10 d (57.1%); the concentration of 25 μg/mL also presented the best proportion of developing follicles for 5 d (68.7%) and 10 d (62.8%). Treatment with 25 μg/mL quercetin resulted in significant ferric reduction for 10 d of culture, but not for 5 d. No difference (P > 0.1) was observed in the production of reactive oxygen species or in the oxidative degradation of lipids between treatments and non-cultivated controls. Treatment with 25 μg/mL quercetin preserved the morphological integrity of the developing follicles for 5 and 10 d of culture, in addition to promoting the best antioxidant potential after 10 d of culture in bovine ovarian fragments.

Recent Developments in Effective Antioxidants: The Structure and Antioxidant Properties

Since the last few years, the growing interest in the use of natural and synthetic antioxidants as functional food ingredients and dietary supplements, is observed. The imbalance between the number of antioxidants and free radicals is the cause of oxidative damages of proteins, lipids, and DNA. The aim of the study was the review of recent developments in antioxidants. One of the crucial issues in food technology, medicine, and biotechnology is the excess free radicals reduction to obtain healthy food. The major problem is receiving more effective antioxidants. The study aimed to analyze the properties of efficient antioxidants and a better understanding of the molecular mechanism of antioxidant processes. Our researches and sparing literature data prove that the ligand antioxidant properties complexed by selected metals may significantly affect the free radical neutralization. According to our preliminary observation, this efficiency is improved mainly by the metals of high ion potential, e.g., Fe(III), Cr(III), Ln(III), Y(III). The complexes of delocalized electronic charge are better antioxidants. Experimental literature results of antioxidant assays, such as diphenylpicrylhydrazyl (DPPH) and ferric reducing activity power assay (FRAP), were compared to thermodynamic parameters obtained with computational methods. The mechanisms of free radicals creation were described based on the experimental literature data. Changes in HOMO energy distribution in phenolic acids with an increasing number of hydroxyl groups were observed. The antioxidant properties of flavonoids are strongly dependent on the hydroxyl group position and the catechol moiety. The number of methoxy groups in the phenolic acid molecules influences antioxidant activity. The use of synchrotron techniques in the antioxidants electronic structure analysis was proposed.

Flavonoids in the Treatment of Diabetes: Clinical Outcomes and Mechanism to Ameliorate Blood Glucose Levels

BACKGROUND

For thousands of years, natural food products have been used as a medicine for treating diseases that affect the human body, including diabetes mellitus (DM). Lately, several investigations have been performed on the flavonoid derivatives of plant origin, and their biological activity has been extensively studied.

METHODS

Given our need to know more mechanisms for treating DM, we performed a thorough research review on treating diabetes mellitus based on flavonoids, their therapeutic potential, and biological action.

RESULTS

Flavonoids reduce complications in addition to their vital role as effective supplements for preventing diabetes mellitus by regulating glucose metabolism, lipid profile, liver enzyme activity, a protein kinase inhibitor, PPAR, and AMPK with NF-κB.

CONCLUSION

The articles that we reviewed showed the positive role of flavonoids, which in a certain way reduce diabetes, but their side effects still need to be studied further.This review is focused on describing the different types of dietary flavonoids along with their mechanisms of reducing blood glucose and enhancing insulin sensitivity, as well as their side effects.

Therapeutic Potential of Flavonoids in Pain and Inflammation: Mechanisms of Action, Pre-Clinical and Clinical Data, and Pharmaceutical Development

Pathological pain can be initiated after inflammation and/or peripheral nerve injury. It is a consequence of the pathological functioning of the nervous system rather than only a symptom. In fact, pain is a significant social, health, and economic burden worldwide. Flavonoids are plant derivative compounds easily found in several fruits and vegetables and consumed in the daily food intake. Flavonoids vary in terms of classes, and while structurally unique, they share a basic structure formed by three rings, known as the flavan nucleus. Structural differences can be found in the pattern of substitution in one of these rings. The hydroxyl group (-OH) position in one of the rings determines the mechanisms of action of the flavonoids and reveals a complex multifunctional activity. Flavonoids have been widely used for their antioxidant, analgesic, and anti-inflammatory effects along with safe preclinical and clinical profiles. In this review, we discuss the preclinical and clinical evidence on the analgesic and anti-inflammatory proprieties of flavonoids. We also focus on how the development of formulations containing flavonoids, along with the understanding of their structure-activity relationship, can be harnessed to identify novel flavonoid-based therapies to treat pathological pain and inflammation.

Glycosylation of 3-Hydroxyflavone, 3-Methoxyflavone, Quercetin and Baicalein in Fungal Cultures of the Genus Isaria

Flavonoids are plant secondary metabolites with a broad spectrum of biological activities. In nature, they occur mainly in the form of glycosides, but their extraction is often difficult and expensive, as is chemical synthesis. We have shown that biotransformations are an excellent method for obtaining flavonoid glycosides. We are the first team to describe the use of Isaria microorganisms in biotransformations of flavonoid compounds. In the present study as biocatalysts, we used one strain of Isaria fumosorosea KCH J2 isolated from a spider carcass in green areas of Wroclaw and two strains of I. farinosa (J1.4 and J1.6) isolated from insects found in already unused mines in Lower Silesia. The substrates were 3-hydroxyflavone, 3-methoxyflavone, quercetin (3,3',4',5,7-pentahydroxyflavone), and baicalein (5,6,7-trihydroxyflavone). For all the substrates that were used in this study, we obtained 4-O-methylglucopyranosides. In the case of substrates with a hydroxyl group in the third position, O-β-d-glucopyranosides were also formed. Isoquercetin that was obtained by biotransformation was used as a substrate to check the kinetics of the formation of flavonoid 4-O-methylglucopyranosides in I. fumosorosea KCH J2 culture. We did not observe the attachment of the methyl group to glucose unit in isoquercetin. Our finding suggest that the attachment of 4-O-methylglucopyranose occurs in one step.

Antioxidant activity of vinegar produced from distilled residues of the Japanese liquor shochu

Rice shochu distilled residue (RSDR) is a byproduct of rice shochu production. RSDR was converted into vinegar by acetate fermentation. In our present study, two major antioxidant compounds, tyrosol and ferulic acid, were identified from the RSDR-derived vinegar. Furthermore, we investigated the antioxidant activity of freeze-dried RSDR-derived vinegar, which was Acetobactor aceti fermentation powder (AFP), in vitro and in vivo. AFP at 0.25 mg/mL or higher concentrations showed an inhibitory effect against lipid peroxidation and cellular GSH depletion in HepG2 cells induced by H(2)O(2) (P < 0.05). We thus considered the potential of AFP in protecting cells against damage induced by H(2)O(2). Its antioxidant activity was evaluated in vivo using carbon tetrachloride (CCl(4))-induced acute liver injury mouse models. Five consecutive days of oral preadministration of AFP dissolved in PBS at 200, 400, and 800 mg/kg body weight significantly suppressed lipid peroxidation in the liver induced by CCl(4) (P < 0.01). Consequently, treatment with AFP at 200 mg/kg body weight or higher doses suppressed the elevation of alanine aminotransferase and aspartate aminotransferase levels in serum (P < 0.05). These findings suggest that RSDR-derived vinegar can be developed as a health food with an antioxidant effect for the prevention of oxidative injury and cancer.

Relaxation effects of lavender aromatherapy improve coronary flow velocity reserve in healthy men evaluated by transthoracic Doppler echocardiography

PURPOSE

It has been reported that mental stress is an independent risk factor for cardiovascular events and impairs coronary circulation. Lavender aromatherapy, one of the most popular complementary treatments, is recognized as a beneficial mental relaxation therapy. However, no study has examined the effect of this therapy on coronary circulation. We aimed to assess the effect of lavender aromatherapy on coronary circulation by measuring coronary flow velocity reserve (CFVR) with noninvasive transthoracic Doppler echocardiography (TTDE).

MATERIAL AND METHODS

We enrolled 30 young healthy men (mean age 34+/-4.7 years, range 24-40 years). Coronary flow velocities in the left anterior descending coronary artery were recorded by TTDE at rest and during hyperemia induced with an intravenous infusion of adenosine triphosphate (ATP). CFVR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity. CFVR was assessed at baseline and immediately after lavender aromatherapy (four drops of essential oil diluted with 20 ml of hot water and inhaled for 30 min). Simultaneously, serum cortisol was measured as a marker of stress hormones. To exclude the relaxation effects of rest, the same measurements were repeated in the same volunteers without aromatherapy as a control study.

RESULTS

CFVR measurements were obtained in all volunteers (100%). Blood pressure and heart rate responses to ATP infusion were not affected by lavender aromatherapy. Serum cortisol significantly decreased after lavender aromatherapy (8.4+/-3.6 to 6.3+/-3.3, p<0.05), but remained unchanged in controls (9.1+/-3.5 to 8.1+/-3.9, p=ns). In addition, CFVR significantly increased after lavender aromatherapy (3.8+/-0.87 to 4.7+/-0.90, p<0.001), but not in controls (3.9+/-0.8 to 3.9+/-0.8, p=ns).

CONCLUSIONS

Lavender aromatherapy reduced serum cortisol and improved CFVR in healthy men. These findings suggest that lavender aromatherapy has relaxation effects and may have beneficial acute effects on coronary circulation.

Anticancer effect of Kalpaamruthaa on mammary carcinoma in rats with reference to glycoprotein components, lysosomal and marker enzymes

A promising approach to reduce the occurrence of cancer is its treatment, specifically by chemical intervention through minor dietary constituents. Epidemiological studies suggest that specific pharmacologically active agents present in the diet might reduce cancer. A remarkable surge of interest in chemoprevention research has, thus, lead to the identification of many phytochemicals of dietary origin as effective potential chemotherapeutic agents. In the present investigation, attempt has been made to study the potency of Kalpaamruthaa (KA), a herbal preparation, against cancer. The changes in level of glycoprotein components, marker enzymes and lysosomal enzymes were carried out in 7,12-dimethylbenz(a)anthracene (DMBA) induced Sprague-Dawley rats. The changes in the body weights and volume were also determined. KA was administered at the dosage level of 100, 200, 300, 400 and 500 mg/kg body weight (BW) in olive oil orally for 14 d, after the induction period is completed (90 d). On administration of KA, the levels of the above enzymes and the changes in the body weights and volume were significantly normalized in a dose dependent manner. The present study shows that KA is effective at the dosage level of 300 mg/kg body weight in mammary carcinoma bearing rats.

Evaluation of Polyphenolic Acid Esters as Potential Antioxidants

Six polyphenolic acid esters were synthesized and their antioxidative properties were evaluated in three model systems [2,2'-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay, 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH)-induced lipid peroxidation system, and the dye-bleaching assay of peroxynitrite radical]. Among these compounds, we found that compounds 4 [3,4-dihydroxy-benzoic acid-(2-phenoxyethyl ester)], and 5 [3,4-dihydroxy-cinnamic acid-(2-phenoxyethyl ester)] provided comparable activity to caffeic acid phenethyl ester (CAPE) in the DPPH model. Compound 3 [2,5-dihydroxy-benzoic acid-(2-phenoxyethyl ester)], was found to be more active than CAPE in the AAPH system, it also displayed about 2-fold greater activity than CAPE in the peroxynitrite radical model. These results suggest that these phenolic acid ester derivatives, with their potent anti-oxidant activities, may have useful applications as antioxidants.

Synthesis and evaluation of caffeic acid amides as antioxidants

A series of amides of caffeic acid has been synthesised and their antioxidant properties evaluated as lipid peroxidation inhibitors. Anilides of caffeic acid were found to be very efficient antioxidants with IC50's of 0.3 microM.