Antioxidant activity of selected plant species; potential new sources of natural antioxidants

The aim of this study was to examine six plants from Serbia for their potential antioxidant activity. Therefore, six antioxidant activity assays were carried out, including: total antioxidant capacity, DPPH free-radical scavenging, the inhibitory activity toward lipid peroxidation, Fe³⁺- reducing power, Fe²⁺- chelating ability and hydroxyl radical scavenging activity. Total phenolic and flavonoid contents were also determined for each alcoholic extract. Cotinus coggygria extract contained the highest amount of total phenols (413 mg GAE /g dry extract), while the highest proportion of flavonoids was found in the Echium vulgare methanol extract (105 mg RU/g). Cotinus coggygria and Halacsya sendtneri alcoholic extracts showed the highest total antioxidant capacity (313 and 231 mg AA/g dry extract), as well as DPPH free-radical scavenging (IC₅₀ = 9 and 99 μg/ml), inhibitory activity toward lipid peroxidation (IC₅₀ = 3 and 17 μg/ml) and reducing power. Whereas, the greatest hydroxyl radical scavenging activity, as well as ferrous ion chelating ability showed Echium vulgare, Echium rubrum and Halacsya sendtneri.     

五味子科植物三萜类化学成分研究进展

对近几年来从五味子科植物中分离到的三萜类成分及药理作用等方面的研究进行综述,并根据萜类成分的结构按其所属的基本骨架进行了分类整理,为五味子科植物的研究提供帮助.     

Aza-CGP37157-lipoic hybrids designed as novel Nrf2-inducers and antioxidants exert neuroprotection against oxidative stress and show neuroinflammation inhibitory properties

Two multitarget hybrids, derived from an aza-analogue of CGP37157, a mitochondrial Na⁺/Ca²⁺ exchanger antagonist, and lipoic acid were designed in order to combine in a single molecule the antioxidant and Nrf2 induction properties of lipoic acid and the neuroprotective activity of CGP37157. The hybrid derivatives showed Nrf2 induction and radical scavenging properties, leading to a good neuroprotective profile against oxidative stress, together with an interesting antineuroinflammatory activity. The results obtained show differences in activity depending on the configuration of the chiral center of LA.     

Antioxidant compounds from the stem bark of Garcinia atroviridis

A new xanthone, namely garcinexanthone G (1), along with eight known compounds, stigmasta-5,22-dien-3β-ol (2), stigmasta-5,22-dien-3-O-β-glucopyranoside (3), 3β-acetoxy-11α,12α-epoxyoleanan-28,13β-olide (4), 2,6-dimethoxy-p-benzoquinone (5), 1,3,5-trihydroxy-2-methoxyxanthone (6), 1,3,7-trihydroxyxanthone (7), kaempferol (8) and quercetin (9), were isolated from the stem bark of Garcinia atroviridis. Their structures were elucidated based on spectroscopic methods including nuclear magnetic resonance (NMR-1D and 2D), UV, IR, and mass spectrometry. All the isolated compounds were evaluated for their antioxidant properties based on the DPPH radical scavenging activities. Results showed that 1,3,7-trihydroxyxanthone and quercetin showed significant antioxidant activities with EC₅₀ values of 16.20 and 12.68 μg/ml, respectively, as compared to the control, ascorbic acid (7.4 μg/ml).     

Chemical composition,antimicrobial, and cytotoxicity studies on S. erianthum and S. macranthum essential oils

Context: Solanum erianthum D. Don and Solanum macranthum Dunal (Solanaceae) are widely used in traditional medicine. The leaves act as an abortifacient and in particular to treat leucorrhoea, sores, and skin irritations.

Objective: This study was undertaken to characterize the volatile constituents of the leaf and fruit essential oils of S. erianthum and S. macranthum; their antimicrobial and in vitro cytotoxic bioassay against human breast and prostate tumor cells.

Methods: The volatile oils were obtained by hydrodistillation and analyzed for their constituents by gas chromatography-mass spectrometry (GC-MS). Minimum Inhibitory Concentrations (MIC) were determined using the microbroth dilution technique while the cytotoxic potentials were evaluated using the Cell Titre 96^(R) AQ_ueous Non-Radioactive Cell Proliferation Assay method.

Results: Solanum erianthum essential oils were characterized by the abundance of α-terpinolene (17.8%), α-phellandrene (17.5%), p-cymene (15.7%) and β-pinene (11.7%) in the leaves; α-humulene (23.1%), humulene epoxide II (20.0%), caryophyllene oxide (16.5%), methyl salicylate (11.8%) and β-caryophyllene (10.9%) in the fruits. The leaf oil of S. macranthum consisted of (E)-phytol (29.0%), pentadecanal (28.1%) and pentadecane (7.7%) while the major fruit oil constituents were α-humulene (36.5%), β-caryophyllene (17.8%), ethyl palmitate (9.4%), and methyl salicylate (8.2%). Solanum erianthum leaf volatile oil demonstrated potent inhibitory activity against Hs 578T and PC-3 human breast and prostate tumor cells respectively. In addition, the Solanum essential oils exhibited significant antimicrobial activity (19.5–625 µg/mL) on pathogens employed in the assay.

Conclusion: The Solanum essential oils possess strong antimicrobial activity in addition to the potent cytotoxic potential of S. erianthum leaf oil against Hs 578T and PC-3 cells.     

In vitro antioxidant and anti-cholinesterase activities of Rhizophora mucronata

Context: Rhizophora mucronata Lam. (Rhizophoraceae), commonly known as Asiatic mangrove, has been used traditionally among Asian countries as folk medicine.

Objective: This study investigates the cholinesterase inhibitory potential and antioxidant activities of R. mucronata.

Materials and method: Rhizophora mucronata leaves were successively extracted using solvents of varying polarity and a dosage of 100–500?µg/ml were used for each assay. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were assessed according to the method of Ellman. In vitro antioxidant activity was assessed using free radical scavenging, reducing power, and metal-chelating activity (duration – 3 months). Total phenolic and flavonoid content were quantified spectrophotometrically. Compound characterization was done using column chromatography, NMR, FTIR, and LC-MS analysis.

Results: Methanolic leaf extract (500?µg/ml) exhibited the highest inhibitory activity against AChE (92.73?±?0.54%) and BuChE (98.98?±?0.17%), with an IC₅₀ value of 59.31?±?0.35 and 51.72?±?0.33?µg/ml, respectively. Among the different solvent extracts, methanolic extract exhibited the highest antioxidant activity with an IC₅₀ value of 47.39?±?0.43, 401.45?±?18.52, 80.23?±?0.70, and 316.47?±?3.56?µg/ml for DPPH, hydroxyl, nitric oxide radical, and hydrogen peroxide, respectively. Total polyphenolic and flavonoid contents in methanolic extract were observed to be 598.13?±?1.85?µg of gallic acid equivalent and 48.85?±?0.70?μg of rutin equivalent/mg of extract. Compound characterization illustrated (+)-catechin as the bioactive compound responsible for cholinesterase inhibitory and antioxidant activities.

Conclusion: The presence of rich source of flavonoids, in particular catechin, might be responsible for its cholinesterase inhibitory and antioxidant activities.     

Antioxidant activity against H2O2-induced cytotoxicity of the ethanol extract and compounds from Pyrola decorate leaves

Context: The leaves of Pyrola decorate H. Andr (Pyrolaceae), known as Luxiancao, have long been used for treating kidney deficiency, gastric haemorrhage and rheumatic arthritic diseases in traditional Chinese medicine.

Objective: The phytochemicals and antioxidant capacities in vitro of P. decorate leaves were investigated.

Materials and methods: Ethanol, petroleum ether, acetidin, n-butyl alcohol and aqueous extracts of Pyrola decorate leaves were prepared by solvent sequential process, and then isolated and purified to obtain phytochemicals. Cell viability was measured by MTT assay. PC12 cells were pretreated for 24?h with different extractions of P. decorate leaves at concentrations of 0.1, 0.5, 1, 5 and 10?mg/mL, then H₂O₂ of 0.4?mM was added in all samples for an additional 2?h. The antioxidant capacities of betulin, ursolic acid and monotropein were determined in PC12 cells against H₂O₂ induced cytotoxicity in vitro as well.

Results: Nine compounds (1–9) were isolated and structurally determined by spectroscopic methods, especially 2D NMR analyses. Ethanol extract treated groups showed inhibitory activity with IC₅₀ value of 10.83?mg/mL. Betulin, ursolic acid and monotropein were isolated from P. decorate, and demonstrated with IC₅₀ values of 6.88, 6.15 and 6.13?μg/mL, respectively.

Discussion and conclusions: In conclusion, Pyrola decorate is a potential antioxidative natural plant and worth testing for further pharmacological investigation in the treatment of oxidative stress related neurological disease.     

Physicochemical Characterization and Antioxidant Activity of Essential Oils of Guggul (Commiphora wightii) Collected from Madhya Pradesh

The present study reports physicochemical characterization and antioxidant activity of essential oils extracted from guggul (Commiphora wightii) exudates collected from different places in Madhya Pradesh, India. The guggul exudates were hydrodistilled for 3-4 h in Clevenger apparatus. The oil obtained was dried over anhydrous Na₂SO₄ and stored at 4° until testing. Before extraction of oils from the exudates, their % moisture and tristimulus values of the colors namely L (white-black), a (green-red) and b (blue-yellow) were determined. Physicochemical characterization of the extracted oils was carried out to determine their solubility, yield%, acid value (mg/KOH/g), saponification value (mg/KOH/g), ester value, iodine value (g/g), peroxide value (mEq/kg) and Fourier transformed infrared analyses. The storage-effect on the % moisture and tristimulus values of the colors of guggul exudates as also the % oil yield and physicochemical parameters of the essential oils extracted from them, were studied using three different packaging materials viz., local plastic, low density polyethylene (200 G) and high density polyethylene (200 G). The antioxidant potential of extracted oils was evaluated by free radical scavenging activity using 1,1-diphenyl-2-picryl hydrazyl assay.     

New p-Substituted Salicylaldehyde Phenylhydrazone Derivatives: Synthesis,Characterization, and Antioxidant Activities

A series of new p-nitrophenylhydrazone derivatives 3a–f were synthesized, characterized, and investigated for their antioxidant activities. These compounds have been synthesized by refluxing (p-nitrophenyl)hydrazine with 4-sub-stituted salicylaldehydes. The structures of the compounds were established by IR, ¹H- and ¹³C-NMR, and MS data. The antioxidant activities (free radical-scavenging activity, reducing power, metal chelating activity, and total anti-oxidant activity) of the hydrazone compounds were evaluated. All of the compounds exhibited significant activities, while compound 3a, with the shortest chain, showed the highest antioxidant activity in all of the tests.     

Antioxidant and antimutagenic activity of Carum copticum fruit extracts

The ajowain (Carum copticum (L.)) is a popular spice and traditionally used in Indian system of medicine. Considering the importance of natural products in modern phytomedicine, the antioxidant and antimutagenic activities of C. copticum fruits extract and its fractions were evaluated. The methanol fraction showed highest antioxidant activity by phosphomolybdenum (2087.7 μmol) and DPPH assay (90.2%) followed by other fractions comparable to ascorbic acid and BHT. Based on antioxidant activity, methanol fraction was evaluated for antimutagenic potential against direct acting mutagens sodium azide (NaN₃) and methyl methane sulphonate (MMS) and indirect acting mutagens 2-aminofluorene (2-AF) and benzo(a)pyrene (B(a)P), using Salmonella typhimurium (TA97a, TA98, TA100, and TA102) tester strains. The methanolic fraction showed no sign of mutagenicity at tested concentrations (25–100 μg/plate). Antimutagenic activity was recorded with inhibition of mutagenicity ranging from 10.8% to 83.1% in a concentration dependent manner. The phytochemical analysis by IR, HPLC, GC–MS, and total phenolic assay revealed a high content of phenolic terpenoids. Further, characterization of active principle is needed to understand the mechanism of action and therapeutic efficacy in vivo.     

Terpenoids with neurite outgrowth-promoting activity from the branches and leaves of Illicium merrillianum

Eighteen terpenoids (1–18) were isolated from Illicium merrillianum. Compound 1 was identified as new compound, and its structure was established by comprehensive spectroscopic analysis and single-crystal X-ray diffraction. All compounds were evaluated for nerve growth factor (NGF)-mediated neurite outgrowth activity using rat pheochromocytoma (PC12) cells as a model system of neuronal differentiation. Compounds 1, 3, 18 showed significant neurite outgrowth-promoting activity in the presence of 20 ng/ml NGF in a dose-dependent manner at concentrations of 1–100 μM after 24-h treatment. Subtle difference of functional groups at C-2 position in hopane-type triterpene resulted in enormous bioactivity difference, compound 1 was neurotrophic but 2 was cytotoxic.     

金钗石斛中的菲类和木脂素类成分及其抗氧化作用

研究金钗石斛茎中的抗氧化活性成分，并探讨它们的构效关系。综合运用现代色谱学和光谱学方法对金钗石斛60％乙醇提取物中的化学成分进行分离鉴定，采用DPPH自由基清除法评价化合物的抗氧化活性。从金钗石斛的活性部位中分离得到5个菲类化合物和4个木脂素类化合物，它们的结构鉴定为流苏菲（1），毛兰菲（2），4-甲氧基菲-2，7-二醇（3），2,5-二羟基-4，9-二甲氧基菲（4），3，7-二羟基-2，4-二甲氧基菲（5），丁香脂素（6），松脂素（7），5′-甲氧基松脂素（8），鹅掌揪树脂醇-A（9）。化合物2和6对DPPH自由基清除活性强于Vc；化合物3，4，5，7，8和9的活性弱于Vc，但强于BHT。所有化合物均为首次报道从金钗石斛中分离得到，化合物3，4和9为首次报道从石斛属植物中分离得到。在DPPH自由基清除法中，酚羟基的邻位存在具有供电作用的甲氧基时对菲类和木脂素类化合物的抗氧化活性具有积极的作用。     

Synthesis and In Vitro Antioxidant Activity of New 3-Substituted-2-Oxindole Derivatives

A series of new 1,3-dihydro-3-hydroxy-3-(2-phenyl-2-oxoethyl)-2H-indol-2-ones (1a-g) and 1,3-dihydro-3-(2-phenyl-2-oxoethylidene)-2H-indol-2-ones (2a-g) were synthesised by Knoevenagel condensation of substituted indole-2,3-diones (isatins) with various acetophenones. The synthesised compounds were characterised by their physical data, elemental, IR, ¹H NMR, ¹³C NMR and mass spectral analyses and their in vitro antioxidant activity was determined by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay. These compounds showed moderate to good antioxidant activities as compared with the standard, ascorbic acid. The antioxidant potential of 3-hydroxy-3-substituted oxindoles (1a-g) increased in a concentration-dependent manner from 10 to 500 μg/ml with 5-fluoro and 5-methyl analogues showing maximum activity. Of 3-aroyl methylene indol-2-ones (2a-g), majority of compounds with halogen substitution at position 5 of isatin ring exhibited good antioxidant activity within a concentration range of 5-100 μg/ml and the maximum activity was observed at 20 and 25 μg/ml concentrations. Thus, our study provides evidence that some newly synthesised isatin derivatives exhibit substantial antioxidant activity at low concentrations.     

Screening of Panamanian Plants for Cosmetic Properties,and HPLC-Based Identification of Constituents with Antioxidant and UV-B Protecting Activities

A library of 600 taxonomically diverse Panamanian plant extracts was screened for DPPH scavenging and UV-B protective activities, and the methanolic extracts of Mosquitoxylum jamaicense, Combretum cacoucia, and Casearia commersionia were submitted to HPLC-based activity profiling. The compounds located in the active time windows were isolated and identified as gallic acid derivatives and flavonoids. Gallic acid methyl ester (3) and digallic acid derivatives (2, 6) showed the highest DPPH scavenging activity (<10 μg/mL), while protocatechuic acid (7) and isoquercitrin (10) exhibited the highest UV-B protective properties.     

Antioxidant evaluation of O-methylated metabolites of catechin, epicatechin and quercetin

Catechins and quercetin are major polyphenols in many plant foods that have been related to health promotion. In the human organism they are largely metabolized to different metabolites, which are further found in plasma and should contribute to the biological effects associated to the intake of the parent compounds. An important step in quercetin and catechins metabolism is the O-methylation of the catechol group, which can be expected to have an effect on their antioxidant and scavenging properties. In the present work, the 3′- and 4′-methylethers of catechin and epicatechin have been prepared and characterised and their antioxidant activity evaluated and compared to that of the corresponding quercetin derivatives. The antioxidant activity was assessed using the ferric reducing power (FRAP) assay and two methods based on the ability to scavenge the ABTS⁺ radical cation at different pH values. In these assays the three flavonoids behave as better radical scavengers and reducing compounds than usually recognised antioxidants like α-tocopherol. The O-methylation of the hydroxyls of the catechol B-ring resulted in a decrease of the antioxidant activity with regard to the parent compounds. However, the methylated metabolites still retain significant radical scavenging activity at pH 7.4, suggesting that they could act as potential antioxidants in physiological conditions. Quercetin and its methylated metabolites showed, in general, greater activity than (epi)catechin and their O-methyl derivatives, although a relatively high antioxidant activity was found in the case of 3′-O-methyl catechin at pH 7.4, comparable to those of its parent compound and the quercetin metabolites. It was confirmed that the antioxidant activity of the flavonoids assayed was strongly dependent on the pH of the medium, showing higher activity at greater pH values. The results obtained are expected to contribute to the understanding of the mechanisms involved in the biological effects attributed to the intake of flavonoid-rich diets.     

苦菊乙酸乙酯提取物的体外抗氧化活性研究

目的:研究苦菊乙酸乙酯提取物(CEE)的体外抗氧化活性。方法:苦菊经95%乙醇加热回流、石油醚脱脂和乙酸乙酯萃取,挥干乙酸乙酯后得到CEE。通过二苯代苦味酰自由基(DPPH.)清除能力、还原能力和2,2′-偶氮-双(-2-脒基丙烷)氯化二氢(AAPH)诱导的红细胞溶血模型,检测CEE的抗氧化活性。结果:在DPPH.清除能力试验中,CEE和阳性对照药的清除率为50%时所需待测液的浓度(EC50)分别为(59.76±6.11)mg·L-1和(3.89±0.23)mg·L-1,两者相差1.54个数量级。CEE和阳性对照药(抗坏血酸)皆能使还原能力测试体系的吸光度增加,并呈浓度-效应关系(P<0.01),但CEE的还原能力不如抗坏血酸(P<0.01)。在AAPH诱导的红细胞溶血模型中,CEE能有效降低兔血红细胞的溶血率(P<0.01),且高剂量(20 mg·L-1)CEE可使溶血率恢复到空白对照的水平。结论:CEE能有效清除自由基,具有一定的还原能力,并对AAPH诱导的兔红细胞溶血具有很好的保护作用。提示CEE具有一定的抗氧化活性,可对其抗氧化活性及其有效成分作进一步的研究。     

鼠尾藻多酚及其各组分的抗凝血活性筛选

目的筛选鼠尾藻多酚及其各组分的抗凝血活性。方法采用膜分离方法对鼠尾藻多酚进行分级;采用毛细管法测定小鼠凝血时间;采用剪尾法测定小鼠出血时间;采用试管法测定新西兰兔激活部分凝血活酶时间、血浆凝血酶原时间和血浆凝血酶时间。结果高相对分子质量(Mr)鼠尾藻多酚分级级分极显著地延长小鼠凝血时间、出血时间、新西兰兔激活部分凝血活酶时间,且其延长程度与多酚Mr成正相关关系,Mr大于1.0×105的组分体内体外抗凝血活性与阿司匹林相近。结论高Mr鼠尾藻多酚具有极显著的体内、体外抗凝血活性。     

鸡骨草醇提物体外抗氧化自由基作用研究

目的 测定鸡骨草(Herba Abri)色素的抗活性氧自由基活性作用,为充分利用鸡骨草资源提供理论依据。方法 以65%乙醇作为溶剂,pH=3条件下浸泡24 h,利用旋转蒸发器减压蒸发辅助法提取鸡骨草色素;通过紫外分光光度法测定鸡骨草色素清除超氧自由基(?O2-)和羟自由基（?OH）能力﹑清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基能力、普鲁士法测定其还原Fe3 能力、以及以丁基羟基茴香醚（butylated hydroxylanisole, BHA）作对照测定鸡骨草色素对金属离子Fe2 螯合能力。结果 鸡骨草色素具有较强的清除超氧自由基(?O2-)、羟自由基（?OH）、DPPH自由基能力,还原Fe3 能力和Fe2 螯合能力。结论 鸡骨草色素具有较强抗氧化作用,其抗氧化性随着浓度的增大而增强。