Flavones with free radical scavenging activity fromGoniothalamus tenuifolius

From the leaves of Goniothalamus tenuifolius, a new natural product namely 3'-hydroxy-3,5,7,4'-tetramethoxyflavone (1) was isolated, along with seven other known compounds (2-8). Each of these isolates was evaluated for free radical scavenging activity on the DPPH decoloration test. The data obtained in this study suggested that the ortho 3',4'-diphenolic structure was essential for the activity of these flavonol derivatives.     

Synthesis and in-vitro antimycobacterial activity of fluoroquinolone derivatives containing a coumarin moiety

A series of gatifloxacin, ciprofloxacin, and 8-OCH(3) ciprofloxacin coumarin derivatives with remarkable improvement in lipophilicity as compared to the parent fluoroquinolones was designed, synthesized, and characterized by (1) H-NMR, MS, and HRMS. These derivatives were evaluated for their in-vitro activity against Mycobacterium smegmatis CMCC 93202 and MTB H37Rv ATCC 27294. All of the synthesized compounds were less active than the parent compounds against M. smegmatis CMCC 93202, but the activity of compound 6 was found to be 2-8-fold more potent than ciprofloxacin, 8-OCH(3) ciprofloxacin, moxifloxacin, and rifampin, and comparable to gatifloxacin against MTB H37Rv ATCC 27294. These results indicated that the lipophilicity of the tested compounds is not the sole parameter affecting antimycobacterial activity.     

Synthesis and antibacterial activity of quinolone-based compounds containing a coumarin moiety

A new series of quinolone-based compounds containing a coumarin moiety have been synthesized and studied for their antibacterial activity against a panel of gram-positive and gram-negative bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The results of the antibacterial evaluation of N-[2-(coumarin-3-yl)ethyl]piperazinyl quinolone derivatives in comparison with parent quinolones (norfloxacin, ciprofloxacin, and enoxacin) indicated that N-[2-(coumarin-3-yl)-2-oxoethyl]ciprofloxacin derivative (compound 8b) showed comparable or more potent antibacterial activity with respect to the reference drugs against the test strains. Generally, in both gram-positive and gram-negative bacteria, better results are obtained with cyclopropyl at the N-1 position of the quinolone ring and 2-oxo- on the ethyl spacer of coumarin and piperazine rings.     

9, 10-Dihydrophenanthrene derivatives from Pholidota yunnanensis and scavenging activity on DPPH free radical

Three new 9,10-dihydrophenanthrene derivatives named phoyunnanins A-C, together with six known 9,10-dihydrophenanthrene constituents, 4,4',7,7'-tetrahydroxy-2,2'-dimethoxy-9,9',10,10'-tetrahydro-1,1'-biphenanthrene (4), lusianthridin (5), eulophiol (6), 2,4,7-trihydroxy-9,10-dihydrophenanthrene (7) and imbricatin (8), were isolated from the 60% ethanolic extract of air-dried whole plant of Pholidota yunnanensis Rolfe. The structures of phoyunnanins A-C were established as 6-[2'-(3',3'-dihydroxy-5'-methoxybibenzy)]-4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (1), 6-[6'-(trans-3',3'-dihydroxy-5'-methoxystilbeny)]-4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (2) and 4,4',7,7'-tetrahydroxy-2,2'-dimethoxy-9,9',10,10'-tetrahydro-1,6'-biphenanthrene (3), respectively, on the basis of the spectroscopic analysis. All eight compounds (1-8) were found to show the DPPH free radical scavenging activity with EC₅₀ from 8.8 to 55.9 μM.     

Free radical scavenging activity and chemical constituents of Urvillea ulmaceae

The methanol extract of Urvillea ulmaceae Kunth (Sapindaceae) aerial parts and the hexane, ethyl acetate, and hydromethanol fractions were evaluated for their free radical scavenging activity with the DPPH assay. Among all the tested fractions, the ethyl acetate fraction was the most active, exhibiting an IC₅₀ of 16.33?μg/mL, comparable to that of the commercial antioxidant BHT. Fractionation of the ethyl acetate fraction through chromatographic methods afforded trans-N-methyl-5-hydroxypipecolic acid, epicatechin, and proanthocyanidin A2 as the main constituents. Epicatechin and proanthocyanidin A2 showed potent DPPH radical scavenging activity, with IC₅₀ values of 18.34 and 11.45?μg/mL, respectively. A new compound, trans-N-methyl-5-hydroxypipecolic acid, did not show any antioxidant effect (IC₅₀?>?500?μg/mL).     

Characterization of the radical scavenging and antioxidant activities of danshensu and salvianolic acid B.

Danshensu (3-(3,4-dihydroxyphenyl) lactic acid) and salvianolic acid B, two natural phenolic acids of caffeic acid derivatives isolated from Salvia miltiorrhiza root of the most widely used traditional Chinese medicine for the treatment of various cardiovascular diseases, have been reported to have potential protective effects from oxidative injury. To better understand their biological functions, the in vitro radical scavenging and antioxidant activities of danshensu and salvianolic acid B were evaluated along with vitamin C. Both danshensu and salvianolic acid B exhibited higher scavenging activities against free hydroxyl radicals (HO()), superoxide anion radicals (O(2)(-)), 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals and 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals than vitamin C. In contrary, danshensu and salvianolic acid B showed weaker iron chelating and hydrogen peroxide (H(2)O(2)) scavenging activities than vitamin C. As expressed as vitamin C equivalent capacity (VCEAC), the relative VCEAC values (mg/100ml) were in the order of salvianolic acid B (18.59) > danshensu (12.89) > vitamin C (10.00) by ABTS radical assay. The protective efficiencies against hydrogen peroxide induced human vein vascular endothelial cell damage were correlated with their antioxidant activities. Analysis of structure-activity relationship of these two compounds showed that the condensation and conjugation of danshensu and caffeic acid appears important for antioxidant activity. These results indicated that danshensu and salvianolic acid B are efficient radical scavengers and antioxidants, and salvianolic acid B is superior to danshensu. Their radical scavenging and antioxidant properties might have potential applications in food and healthcare industry.     

香樟叶不同溶剂提取物清除DPPH自由基的研究

目的研究香樟叶不同溶剂提取物清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基的作用,筛选出香樟叶清除自由基活性的有效部位。方法采用系统溶剂法将香樟叶的乙醇提取物分成石油醚、三氯甲烷、乙酸乙酯、正丁醇和水5种溶剂提取物,采用DPPH自由基体系法测定其抗氧化活性。结果香樟叶的石油醚、三氯甲烷、乙酸乙酯、正丁醇和水溶剂提取物对DPPH的IC50分别为6.003 8、1.329 8、0.398 7、0.346 7、5.087 0mg·mL-1。结论香樟叶不同溶剂提取物均有抗氧化活性,其正丁醇提取物的抗氧化能力最强。     

A radical scavenging Farnesylhydroquinone from a marine-derived fungusPenicillium sp.

Farnesylhydroquinone (1) has been isolated from the mycelium of a marine-derived fungus of the genus Penicillium. The structure of the compound (1) has been elucidated by spectral method. The compound 1 exhibits potent radical scavenging activity (IC50 12.5 microM) against the DPPH.     

Interactions of herbal extract combinations against free radical scavenging activity

Herbal medicines are often combinations of herbal extracts that are assumed to have additive or synergistic effects. This investigation compared the effect of individual herbal extracts with combinations of extracts on antioxidant activity by 1,1-diphenyl picryl hydrazyl (DPPH) method and showed the additive or synergistic effects by studying interactions between herbal extracts in combination. Curcuma longa Linn. (Zingiberaceae), Bacopa monneira Linn. Penn. (Scrophulariaceae), Zingiber officinale Rosc. (Zingiberaceae) and Emblica officinalis Gaertn. (Euphorbiaceae) were collected and used to prepare the extracts. Effects of the extracts on DPPH scavenging activity were estimated quantitatively by a UV-spectrophotometeric method. Combinations of two herbal extracts of the four active extracts and their interactions were tested by the DPPH method. Each extract significantly scavenges the free radical activity in a dose-dependent manner. The active extracts of Curcuma longa, Bacopa monneira, Zingiber officinale and Emblica officinalis were tested as two-extract combinations. Curcuma longa and Bacopa monneiera, when combined, showed additive effect with a trend towards synergistic effect, whereas Curcuma longa and Emblica officinalis together were additive. The four extracts together were significantly (p?≤?0.01) more effective than the two-by-two combinations and the individual extracts alone. The less predictable nature of the two-way combinations suggests a need for careful characterization of the effects of each individual herb based on their intended use.     

Norlignan derivatives from <Emphasis Type="Italic">Curculigo crassifolia</Emphasis> and their DPPH radical scavenging activity

A novel norlignan derivative, crassifogenin C (1), and a known compound, curcapital (2), were isolated from the ethanolic extract of the rhizomes of Curculigo crassifolia. Their structures were elucidated on the basis of spectroscopic evidence and comparisons with literature data. Curcapital (2) was isolated from this plant for the first time. The free radical scavenging activity of the isolated compounds along with crassifoside E (3) and crassifoside F (4), which were reported previously, was evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. All compounds showed strong radical scavenging activity. The primary structure-activity relationship is also discussed.     

Free radical scavenging activity of silibinin in nitrite-induced hemoglobin oxidation and membrane fragility models

Free radical formation in heme proteins is recognized as a factor in mediating the toxicity of many drugs. Xenobiotics and drug therapy-related toxicity, due to oxidative modification of hemoglobin (Hb), has been attributed in part to the uncontrolled oxidative reactions. A variety of antioxidant strategies to ameliorate potential oxidative damage in vivo have been suggested. The present study was designed to evaluate the dose–response relationship of the free radical scavenging properties of silibinin dihemisuccinate (SDH) in nitrite-induced Hb oxidation in vitro and in vivo. Different concentrations of SDH were added, before and after different intervals of inducing Hb oxidation in erythrocytes lysate, and formation of methemoglobin (MetHb) was monitored spectrophotometrically; the same approach was utilized to evaluate the effect of the same doses of SDH on the integrity of erythrocytes after induction of hemolysis. Moreover, the most effective dose of SDH was administered in rats before challenge with toxic dose of sodium nitrite, and MetHb formation was monitored as mentioned before. The results showed that in both in vitro and in vivo models, SDH successfully attenuates Hb oxidation after challenge with sodium nitrite; this protective effect was not related to the stage of the catalytic stage of Hb oxidation, though the effect was more prominent when the compound was administered before nitrite. In conclusion, SDH can effectively, in concentration-dependent pattern, attenuate sodium nitrite-induced Hb oxidation and maintain integrity of red blood cells both in vitro and in vivo.     

Neuroprotective and free radical scavenging activities of phenolic compounds fromHovenia dulcis

The EtOAc-soluble fraction from a methanolic extract of Hovenia dulcis Thunb. exhibited neuroprotective activity against glutamate-induced neurotoxicity in mouse hippocampal HT22 cells. The neuroprotective activity-guided isolation resulted in 8 phenolic compounds (1-8), such as vanillic acid (1), ferulic acid (2), 3,5-dihydroxystilbene (3), (+)-aromadendrin (4), methyl vanillate (5), (-)-catechin (6), 2,3,4-trihydrobenzoic acid (7), and (+)-afzelechin (8). Among these, compounds 6 and 8 had a neuroprotective effect on the glutamate-induced neurotoxicity in HT22 cells. Furthermore, compound 6 had a DPPH free radical scavenging effect with an IC50 value of 57.7 microM, and a superoxide anion radical scavenging effect with an IC50 value of 8.0 microM. Both compounds 6 and 8 had ABTS cation radical scavenging effects with IC50 values of 7.8 microM and 23.7 microM, respectively. These results suggest that compounds 6 and 8 could be neuroprotectants owing to their free radical scavenging activities.     

Free radical scavenging and tyrosinase inhibition activity of oils and sericin extracted from Thai native silkworms (Bombyx mori)

Oils and sericin were extracted from pupae and silk cocoons, respectively, of the five Thai native silkworms (Bombyx mori, Linnaeus (Bombycidae)), namely, Keawsakol, Nangnoi, Somrong, Nangleung, and Noneruesee, which are variations of the same species. The oils were extracted by a hot process using Soxhlet apparatus and a cold process using petroleum ether, while sericin was extracted by basic hydrolysis and autoclaving. Sericin from the five Thai native silkworms showed free radical scavenging activity lower than the standard antioxidants (vitamin C, vitamin E, and BHT) by about 20–100-fold, but all oils gave higher activity than that of the standard linoleic acid by 11–22-fold. Oil extracted from Noneruesee by the cold process gave the highest DPPH scavenging activity, compared with other oil samples. All sericin samples showed tyrosinase inhibition activity with IC₅₀ values in the range of 1.2–18.76?mg/mL, but only oils from Noneruesee extracted by the hot process, and Nangleung, Somrong, and Noneruesee extracted by the cold process, showed this activity. Oil extracted by the hot process and sericin by basic hydrolysis from Noneruesee gave the highest tyrosinase inhibition activity, but lower than that of the standards vitamin C and kojic acid by 20–49 and 3–8 times, respectively. This study has suggested that sericin and oil from Noneruesee extracted by basic hydrolysis and the cold process, which gave the highest tyrosinase inhibition and free radical scavenging activity, respectively, can be applied in antiaging and whitening cosmetic products.     

Free radical scavenging activity of conjugated linoleic acid as single or mixed isomers

Context: Conjugated linoleic acids (CLAs) are a mixture of positional and geometric isomers of linoleic acid (LA) and believed to have many positive biological activities.

Objective: The present study was undertaken to assess the antioxidant activity of cis-9, trans-11 and trans-10, cis-12 as single or mixed CLA isomers at two ratios, 1:6 and 1:13 (trans-10, cis-12/cis-9, trans-11).

Materials and methods: A microplate reader was used to determine the free radical scavenging properties of CLAs against DPPH radical in ethanol.

Results: The kinetic reactions of CLA-DPPH^? showed that all tested CLAs have exerted radical scavenging activities in a dose-dependent manner and observed to immediately react and quench DPPH radicals at all tested levels and no lag phase was noticed in CLA-DPPH^? reactions. The median inhibitory concentration (IC₅₀) value for cis-9, trans-11 CLA was observed to be more effective than other tested CLA. Total antioxidant capacity (TAC) of all tested CLAs were less effective radical scavengers as compared to vitamin E and butylated hydroxytoluene, although all tested CLAs were quenched a high amount (P?<?0.05) of DPPH free radicals.

Discussion and conclusion: All tested CLAs have the ability to directly react and quench DPPH free radicals in ethanol. Furthermore, trans-10, cis-12 CLA has greater maximal efficacy than other tested CLAs as free radical scavenger, while cis-9, trans-11 CLA is the most potent isomer to directly react and quench free radicals at low concentrations in the system, suggesting that the free radical scavenging activity of CLA isomers may contribute to their diverse biological activities.     

Antioxidant,free radical scavenging activities of Salvia brachyantha and its protective effect against oxidative cardiac cell injury

In this study, antioxidant and free radical scavenging activities of an endemic Salvia species (Salvia brachyantha (Bordz) probed. was assessed in vitro using 1,1-diphenyl-2-picryhydrazyl (DPPH) radical, β-carotene linoleic acid, superoxide anion radical, hydroxyl radical, and reducing power assays. Regarding our data, the plant extract exhibited antioxidant and radical scavenging activities at different magnitudes of potency. In addition, this study was undertaken to assess whether methanol extract of S. brachyantha could increase the endogenous antioxidant enzymes in cells, and where such increased cellular defences could provide protection against oxidative cell injury. Pre treatment of rat heart cell lines with 100 μg/ml of plant extract for 24 h significantly prevented cell damage and enhanced activity of antioxidant enzymes induced by a treatment with xanthine/xanthine oxidase. Increased reactive oxygen species and cell apoptosis induced by xanthine/xanthine oxidase was dose-dependently prevented when cells were pre treated for 24 h with plant extract. These results indicated that S. brachyantha could protect against cell injury via induction of the antioxidant enzyme defences. The extract of this plant might be valuable antioxidant natural sources and seemed to be applicable in both healthy medicine and food industry.     

Pressurized liquid extraction of phenolic compounds from Anatolia propolis and their radical scavenging capacities

Propolis samples from important honey producing locations of Anatolia namely; Bingol (BG), Rize (RZ), Tekirdag (TK) and Van (VN), were evaluated for their antiradical capacities, total phenolic contents and individual phenolic compounds which was recovered by means of pressurized liquid extraction (PLE). Several extraction parameters of PLE such as; temperature, pressure, solvent type, extraction time and cell size were investigated for their effects on the extraction performances. The results showed that, 40 °C, 1500 psi, Ethanol:water:HCl; (70:25:5, v/v/v) containing 0.1% tert-butylhydroquinone (tBHQ) as solvent, three extraction cycles within 15 min, and a cell size of 11 mL was the most favorable PLE operating conditions. Results of the tests performed to designate the success of the polyphenol analysis showed that the recovery was in the range of 97.2% and 99.7%.Major phenolic compounds in all samples were found to be gallocatechin (GCT), catechin (CT), epicatechin gallate (ECTG), caffeic acid (CA), chlorogenic acid (ChA), and myricetin (Myr). ChA level of BG propolis was 4.5, 3 and 23 times higher than that of RZ, TK and VN region, respectively. Antiradical tests showed that all propolis samples have superior antiradical capacities up to 500 mg Trolox equivalent activity per gram of extract.     

Structure-activity relationship of coumarin derivatives on xanthine oxidase-inhibiting and free radical-scavenging activities

We employed 1,1-diphenyl-2-picrylhydrazyl hydrate (DPPH)- and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-electron spin resonance (ESR) to study the effects of suppression of reactive oxygen species (ROS) by eight selected coumarin derivatives under oxidative conditions. Esculetin was the most potent radical scavenger among the eight tested compounds. Our results suggest that the number of hydroxyl groups on the ring structure of coumarins is correlated with the effects of ROS suppression. We also investigated the effect of the derivatives on the inhibition of xanthine oxidase (XO) activity, and the structure-activity relationships (SARs) of these derivatives against XO activity were further examined using computer-aided molecular modeling. All determined derivatives competitively inhibited XO. The results of the structure-based molecular modeling exhibited interactions between coumarins and the molybdopterin region of XO. The carbonyl pointed toward the Arg880, and the ester O atom formed hydrogen bonds with Thr1010. Esculetin, which bears two hydroxyl moieties on its benzene rings, had the highest affinity toward the binding site of XO, and this was mainly due to the interaction of 6-hydroxyl with the E802 residue of XO. The hypoxanthine/XO reaction in the DMPO-ESR technique was used to assess the combined effect on enzyme inhibition and ROS suppression by these coumarins, and the results showed that esculetin was the most potent agent among the tested compounds. We further evaluated the effects of the test compounds on living cells, and esculetin was still the most potent agent at protecting cells against ROS-mediated Abeta-damage among the tested coumarins.     

盐炙对广西余甘子中黄酮类成分清除DPPH自由基谱效关系的影响

目的:分析盐炙对广西余甘子中黄酮类成分清除DPPH自由基(1,1-二苯基-2-苦肼基)谱效关系的影响.方法:采用高效液相色谱法,建立13批广西不同产地余甘子盐炙前后黄酮类成分的HPLC指纹图谱,结合DPPH自由基体外抗氧化试验,用改进的灰色关联分析法分析整体的指纹图谱与药效之间的关联.结果:确定了20个特征共有峰,清除...     

In vitro screening of essential oil from young and mature leaves of Artemisia scoparia compared to its major constituents for free radical scavenging activity

The present study investigated the chemical characterization, and antioxidant activity of essential oil hydrodistilled from young and mature leaves of Artemisia scoparia. GC–MS analyses revealed a monoterpenoid nature (64–67%) with 44 and 31 constituents in young and mature leaves oil, respectively. The oil from young leaf contained greater amount of oxygenated compounds. β-Myrcene (24.13%) and p-cymene (27.06%) were the major constituents in young and mature leaves oil, respectively. A. scoparia leaf oils (25–200 μg/ml) exhibited a strong 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity and antioxidant activity against hydroxyl radical and hydrogen peroxide. However, the activities of major constituent monoterpenes, β-myrcene and p-cymene, were less. In general, the DPPH radical scavenging and antioxidant activity was in the order: mature leaf oil > young leaf oil > β-myrcene > p-cymene.     

Synthesis and antioxidant properties of (3,4-dihydroxyphenyl)(2,3,4-trihydroxyphenyl)methanone and its derivatives

(3,4-Dihydroxyphenyl)(2,3,4-trihydroxyphenyl)methanone (5) and its two derivatives with bromine were synthesized from reactions such as bromination and demethylation of (3,4-dimethoxyphenyl)(2,3,4-trimethoxyphenyl)methanone (6). The Wolf-Kishner reduction product (9) of 6 and its three derivatives with bromine were obtained. 4-(3,4-Dihydroxybenzyl)benzene-1,2,3-triol and its dibromide derivative (16) were also synthesized from 9 and the corresponding dibromide derivative. The in vitro antioxidant activities of nine new compounds synthesized in these reactions were determined by analyzing the radical scavenging activities of bromophenols for 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picryl-hydrazyl (DPPH), N,N-dimethyl-p-phenylenediamine (DMPD), and the superoxide anion radical (O(2)(·-)) and examining the total reducing power through Fe(3+)-Fe(2+) transformation, FRAP and CUPRAC assays and the ferrous ions (Fe(2+)) chelating activities. Moreover, the results of these activities were compared to those of standard antioxidant compounds such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol, and trolox. The results showed that the synthesized bromophenols had effective antioxidant power. The phenol 5 with two phenolic rings and five phenolic hydroxyl groups was the most potent antioxidant and radical scavenger. In conclusion, the new compounds are promising molecules to be used owing to their potential antioxidant properties.