HPLC determination of phenolic acids and antioxidant activity in concentrated peat extract--a natural immunomodulator

The aim of this study was to devise a method for identification and quantification of phenolic acids in concentrated peat extract samples. The simple reversed-phase HPLC method for simultaneous determination of several phenolic acids was developed. The method was validated and it was suitable for the analysis of phenolic acids in peat extracts. This method allowed identifying eight phenolic acids in peat extracts. Phenolic profiles of two samples of peat extract obtained from different medicinal peats were similar, although variations in amounts of individual phenolic acids were observed. Also, slight variations in total phenolic content were detected. The antioxidant activity of peat extracts was evaluated with spectrophotometric ABTS assay. Differences in antioxidant activity were observed for two samples of peat extract produced from different peat varieties. This differences probably reflected phenolic composition of peat extracts.     

Analysis of phenolic compounds and radical scavenging activity of Echinacea spp

The aim of this study was to set up and validate an RP-LC method with DAD-detection to quantify caffeic acid derivatives in various Echinacea spp. Samples were extracted with 80% methanol. The analyses were carried out on a Lichrospher RP-18 column (125 mm x 4 mm i.d., 5 microm), with a mobile phase gradient, which increases the acetonitrile level in a phosphoric acid solution (0.1%). The flow rate was 1.5 ml/min. Detection was set at 330 nm. This method allowed the identification and quantification of caftaric acid, chlorogenic acid, caffeic acid, cynarin, echinacoside and cichoric acid in Echinacea roots and derivatives. The total phenolic content was 10.49 mg/g for E. angustifolia, 17.83 mg/g for E. pallida and 23.23 mg/g for E. purpurea. Among Echinacea commercial herbal medicines, a certain variability in the concentrations of phenolic compounds was observed. The radical scavenging activity of Echinacea methanolic extracts was evaluated in vitro with a spectrophotometric method based on the reduction of an alcoholic 2,2-diphenyl-1-picrylhydrazyl (DPPH*) radical solution at 517 nm in the presence of a hydrogen donating antioxidant. As for pure compounds, echinacoside had the highest capacity to quench DPPH* radicals (EC50 = 6.6 microM), while caftaric acid had the lowest (EC50 = 20.5 microM). The average EC50 values for E. purpurea, E. pallida and E. angustifolia were 134, 167 and 231 microg/ml, respectively. The radical scavenging activity of Echinacea root extracts reflected their phenolic composition. The results indicate that Echinacea roots and derivatives are a good source of natural antioxidants and could be used to prevent free-radical-induced deleterious effects.     

A phenolic glucoside isolated fromPrunus serrulata var.spontanea and its peroxynitrite scavenging activity

A new phenolic glucoside (1), pursargentoside, was isolated from the leaves of Prunus serrulata var. spontanea, along with three other known compounds, orobol 7-omicron-glucoside (2), 1beta, 2alpha, 3alpha, 24-tetrahydroxy-urs-12-en-28-oic acid (3), and chlorogenic acid (4). The structure of pursargentoside (1) was identified by spectroscopic data analysis including 1D and 2D NMR spectroscopy, as 2-omicron-beta-(6'-benzoyl)-glucopyranosyl omicron-(Z)-coumaric acid. Compounds 1, 2, and 4 exhibited ONOO scavenging activity, whereas compound 3 was determined to be virtually inactive.     

Synthesis, antimicrobial and antioxidant activity of some oxindoles

The present work describes the synthesis and spectral analysis of some new 3(Z)-{4-[4-(arylsulfonyl)piperazin-1-ylbenzylidene)-1,3-dihydro-2H-indol-2-one (5a-j). Ten of the synthesized compounds were screened in vitro against six species of microorganisms, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, Asperigellus niger and Asperigellus clavatus. Most of the compounds exhibited significant antimicrobial activity. All of these compounds were also screened in vitro for the antioxidant activity using DPPH assay. Most of them have shown very significant antioxidant activity.     

Antimutagenic, antioxidant and free radical scavenging activity of ethyl acetate extracts from white, yellow and red onions.

The beneficial effects of red, yellow and white onion extracts have been assessed by antioxidant activity and antimutagenic activity. And the effects compared to BHT and ascorbic acid. Total phenolic compounds and flavonoids in onion extracts were determined. Yellow onion extract had more organic acid and free sugar than those detected in the white and red onion extract. The scavenging activity of DPPH radical and H(2)O(2) were increased depending on the concentration. The antioxidant activities using beta-carotene-linoleate system and reducing power were increased but the effect was small to that of BHT and ascorbic acid. After digested, extracts showed antimutagenic activities, and it seems that they inhibit the mutagenicity for digesting. This study demonstrated that the antimutagenicities and antioxidant properties of ethyl acetate extract against mutagens were related to their phenols and flavonoids, which are heat stable and losses digestive juices are relatively low.     

Determination of hydrogen peroxide scavenging activity of cinnamic and benzoic acids employing a highly sensitive peroxyoxalate chemiluminescence-based assay: structure-activity relationships

A series of cinnamic acids along with their corresponding benzoate analogues were tested for their ability to scavenge hydrogen peroxide (H(2)O(2)), by using a highly sensitive, peroxyoxalate chemiluminescence assay. Among benzoic acid derivatives, vanillic acid (3-hydroxy-4-methoxybenzoic acid) was found to be the most efficient H(2)O(2) scavenger with its hydrogen peroxide scavenging activity (SA(HP)) being 170.20 microM(-1), whereas protocatechuic acid (3,4-dihydroxybenzoic acid) exhibited the weakest activity (5.90 microM(-1)). Caffeic acid (3,4-dihydroxycinnamic acid) was the strongest antioxidant amongst cinnamate derivatives with a SA(HP) = 8.2 microM(-1), as opposed to m-coumaric acid (2-hydroxycinnamic acid), which was found to be a poor hydrogen peroxide scavenger (SA(HP) = 0.18 microM(-1)). Comparison between the two groups revealed that benzoate derivatives are much stronger hydrogen peroxide quenchers in relation with their cinnamate analogues, and this finding was discussed on a basis of structure-activity relationships and comparative assessment of other antioxidant characteristics.     

Primaquine-NSAID twin drugs: Synthesis, radical scavenging, antioxidant and Fe2+ chelating activity

Novel primaquine conjugates with non-steroidal anti-inlammatory drugs (PQ-NSAIDs, 4a-h) were prepared, fully chemically characterized and screened for radical scavenging and antioxidant activities. The synthetic procedure leading to twin drugs 4a-h involved two steps: i) preparation of NSAID benzotriazolides 3a-h from the corresponding NSAID (ibuprofen, ketoprofen, fenoprofen, ketoprofen hydroxy and methylene analogues, diclofenac or indomethacin) and benzotriazole carboxylic acid chloride (BtCOCl, 1), ii) reaction of intermediates 3a-h with PQ. The prepared PQ-NSAIDs exerted moderate activities in the DPPH free radical test and β-carotene-linoleic acid assay. Moreover, ketoprofen derivatives 4d and 4b demonstrated a notable Fe2+ chelating ability as well. On the other hand, negligible antiproliferative and antituberculotic effects of conjugates 4a-h were observed.     

Antitumor activity of some phenolic components in plants

The activity-guided fractionation of some medicinal plants led to yield five kinds of natural stilbene compounds namely 3,5-dihydroxy-4′-methoxystillbene(I), rhapontigenin(II), resveratrol (III), rhaponticin(IV) and piceid(V) and two common flavonoids, apigenin(VI) and luteolin(VII) as active principles of the antitumor property, in vitro, against five kinds of human tumor cell lines, A-549, SK-OV-3, SK-MEL-2, XF-498 and HCT15.     

Synthesis, antioxidant and antiinflammatory activity of novel aryla-cetic and aryl-hydroxamic acids

Four new aryl-acetic acids and the corresponding hydroxamic acids were synthesized. These compounds showed interesting interaction with the free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH), scavenging activity on .OH, inhibition of soybean lipoxygenase and a significant inhibition of carrageenin induced paw edema in rats (44.1-70.9%) at a concentration of 0.01 mmol/100 g.     

The antioxidant activity of some curcuminoids and chalcones

The antioxidant properties of the synthetic compound (C1)–(C8), which comprised 7 curcuminoids and a chalcone, were evaluated by two complementary assays, DPPH and β-carotene/linoleic acid. It was found that, in general, the free radical scavenging ability of (C1)–(C8) was concentration-dependent. Compounds (C1) and (C4), which contained (4-OH) phenolic groups, were found to be highly potent antioxidants with higher antioxidant values than BHT suggesting that synthetic curcuminoids are more potent antioxidants than standard antioxidants like BHT. Using β-carotene-linoleic acid assay, only the water-soluble 2, 4,6-trihydroxyphenolic chalcone (C5) showed 85.2 % inhibition of the formation of conjugated dienes reflecting on its potent antioxidant activity.     

Antidiabetic and antioxidant activity of hydroxycinnamic acids from Calamintha Officinalis Moench.

This study was undertaken to investigate the antidiabetic and antioxidant activities of crude extracts and pure compounds from the aerial parts of Calamintha officinalis Moench. (Lamiaceae). The aqueous extract showed the promising antidiabetic and antioxidant activities. Based on these findings, the aqueous extract was fractionated on a silica gel column chromatography in a bioassay-guided fractionation affording two known hydroxycinnamic acids showing potent activity (1) rosamarinic acid and (2) caffeic acid. Both rosamarinic acid and caffeic acid exhibited significant activity, even more than the positive control, glibenclamide. The results indicated that Calamintha officinalis aqueous extract and the isolated compounds are potential natural agents for the control of diabetes.     

Synthesis of phenolic acid conjugated chitooligosaccharides and evaluation of their antioxidant activity

In this study, eight kinds of phenolic acid conjugated chitooligosaccharides (PA-c-COSs) with different substitution groups, including p-hydroxyl {hydroxybenzoic acid-c-COS (HBA-c-COS), p-coumaric acid-c-COS (PCA-c-COS)}, 3,4-dihydroxyl {protocatechuic acid-c-COS (PTA-c-COS), caffeic acid-c-COS (CFA-c-COS)}, 3-methoxyl-4-hydroxyl {vanillic acid-c-COS (VNA-c-COS), ferulic acid-c-COS (FRA-c-COS)} and 3,5-dimethoxyl-4-hydroxy {syringic acid-c-COS (SRA-c-COS), sinapinic acid-c-COS (SNA-c-COS)}, were prepared by amide coupling reaction. Their antioxidant properties were evaluated using several in vitro models such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (OH) and nitric oxide (NO) radicals scavenging and reducing power assays. The structures of the synthesized compounds were confirmed by UV, FT-IR and (1)H NMR data. CFA-c-COS showed 81.6% and 89.8% scavenging against DPPH and NO radical formation, respectively. CFA-c-COS also showed higher reducing power and hydroxyl radical scavenging activity compared to those of other compounds. Hence, CFA-c-COS can be a potential antioxidant compound.     

In vitro antioxidant activity and scavenging effects of Cinnamomum verum leaf extract assayed by different methodologies.

The free radical scavenging capacity and antioxidant activities of the methanolic extract of Cinnamomum verum leaf (CLE) were studied and compared to antioxidant compounds like trolox, butylated hydroxyl anisole, gallic acid and ascorbic acid. The CLE exhibited free radical scavenging activity, especially against DPPH radical and ABTS radical cation. They also exhibited reducing power and metal ion chelating activity, along with hydroxyl radical scavenging activity. The peroxidation inhibiting activity of CLE recorded using the linoleic acid emulsion system, showed very good antioxidant activity.     

Antimicrobial activity of some hydroxamic acids

Several hydroxamic acids, viz., N-benzyl-N'-hydroxysuccinamide (BHS), poly[alpha,beta-(N-hydroxy)-DL-aspartamide] (PHA), poly[alpha,beta-(N-hydroxy-N-methyl-DL-aspartamide)] (PMHA) and poly[alpha,beta-(N-hydroxy)-DL- aspartamide]/poly[alpha,beta-(N-2-hydroxyethyl)-DL-aspartamide] (PHA-PHEA 1:1) were prepared and screened for their antimicrobial activity. Ten Gram-positive and 7 Gram-negative species of bacteria, 5 Candida species, 4 dermatophyte species and 3 mould species were used in tests. Compound showed no antimicrobial activity on any of the tested microorganisms. Other compounds showed a narrow spectrum of antibacterial activity, but no antifungal activity.     

Radical scavenging and xanthine oxidase inhibitory activity of phenolic compounds from Bridelia ferruginea stem bark

Bridelia ferruginea Benth. (Euphorbiaceae) is a subtropical medicinal plant widely used in traditional African medicine against various diseases, including rheumatic pains. Seven of its constituents (3-O-methylquercetin (1), 3,7,3',4'-tetra-O-methylquercetin (rutisin, 2), myricetin (3), 3',4',5'-tri-O-methylmyricetin (ferrugin, 4), 3,3',4',5'-tetra-O-methylmyricetin (5), quercetin 3-O-glucoside (6), and a biflavanol gallocatechin-[4'-O-7]-epigallocatechin (7)) have been evaluated in-vitro in the xanthine-xanthine oxidase enzymatic system for inhibition of xanthine oxidase and radical scavenging activity. Results indicated that compounds 1, 3, 4 and 6 exhibited, at different levels, xanthine oxidase inhibiting and superoxide scavenging activity at micromolar concentrations, whereas compound 7 showed scavenging activity only. Compounds 2 and 5 were inactive in both cases. Study of the structure-activity relationship demonstrated that for flavonoids the xanthine oxidase inhibitory activity was reduced by methylation of the hydroxyl functionality at C-3 and in rings A and B. These results may partly explain and support the use of B. ferruginea stem bark for the treatment of rheumatic pains in traditional medicine.     

Hydrogen peroxide affects contractile activity and anti-oxidant enzymes in rat uterus

Background and purpose:

The effects of hydrogen peroxide (H₂O₂) on uterine smooth muscle are not well studied. We have investigated the effect and the mechanism of action of exogenous hydrogen peroxide on rat uteri contractile activity [spontaneous and calcium ion (Ca²⁺)-induced] and the effect of such treatment on anti-oxidative enzyme activities.

Experimental approach:

Uteri were isolated from virgin Wistar rats and suspended in an organ bath. Uteri were allowed to contract spontaneously or in the presence of Ca²⁺ (6 mM) and treated with H₂O₂ (2 µM–3 mM) over 2 h. Anti-oxidative enzyme activities (manganese superoxide dismutase-MnSOD, copper-zinc superoxide dismutase-CuZnSOD, catalase-CAT, glutathione peroxidase-GSHPx and glutathione reductase-GR) in H₂O₂-treated uteri were compared with those in uteri immediately frozen after isolation or undergoing spontaneous or Ca²⁺-induced contractions, without treatment with H₂O₂. The effect of inhibitors (propranolol, methylene blue, L-NAME, tetraethylamonium, glibenclamide and 4-aminopyridine) on H₂O₂-mediated relaxation was explored.

Key results:

H₂O₂ caused concentration-dependent relaxation of both spontaneous and Ca²⁺-induced uterine contractions. After H₂O₂ treatment, GSHPx and MnSOD activities were increased, while CuZnSOD and GR (In Ca²⁺-induced rat uteri) were decreased. N^ω-nitro-L-arginine methyl ester antagonized the effect of H₂O₂ on Ca²⁺-induced contractions. H₂O₂-induced relaxation was not affected by propranolol, potentiated by methylene blue and antagonized by tetraethylamonium, 4-aminopyridine and glibenclamide, with the last compound being the least effective.

Conclusions and implications:

H₂O₂ induced dose-dependent relaxation of isolated rat uteri mainly via changes in voltage-dependent potassium channels. Decreasing generation of reactive oxygen species by stimulation of anti-oxidative pathways may lead to new approaches to the management of dysfunctional uteri.     

On the anti-inflammatory activity of some substituted phenolic compounds

Some substituted dihydroxybenzenes have been examined for suppression of the yeast-induced inflammatory reaction in the rat paw. This anti-inflammatory activity is greatest in those compounds derived from resorcinol and in particular the halogenated 5-methylresorcinols. The significance of the internuclear distance between the hydroxyl groups in the meta-position to each other in resorcinol and the importance of the enhanced activity due to the halogen atom(s) is discussed. In this series the toxicity and activity could not be divorced.     

Synthesis, docking studies and antioxidant activity of some chalcone and aurone derivatives

Chalcones and aurones are found to possess high antioxidant activity. They are known to inhibit tyrosinase enzyme involved in synthesis of melanin. A series of substituted chalcones and aurones have been synthesized and tested for their antioxidant activity. Postulated structures of the newly synthesized compounds are in agreement with their IR, ¹H NMR and MS. The docking study of this series of compounds was performed on crystal structure of tyrosinase from Bacillus megaterium using VlifeMDS 3.0 software. Antioxidant activity data obtained from four methods, i.e., DPPH free radical scavenging assay, iron chelating assay, reducing power assay and hydrogen peroxide scavenging assay, indicate that the activity increased with dimethylamino group on position 4/4′ of ring B as evident from the significant activities of SB7 and SB8 in case of chalcones and aurones, respectively. The poor activities of SB4 and SB5 in DPPH scavenging ability and reducing power assays could be because of presence of chloro group on B-ring. Furthermore, the activity is facilitated with the presence of hydroxyl group on A-ring (preferably on position 5/5′) in both chalcones and aurones.