Antioxidant activity of humic acids in radical-chain oxidation processes

Efimova, I. V.; Khil’ko, S. L.; Smirnova, O.V.

doi:10.1134/s1070427212090091

Cited by 19 publications

(17 citation statements)

References 3 publications

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“…Interaction of the proton of these oxygen-containing functional groups in the structure of HAs (HA–H) with the active free radical DPPH• is responsible for the ability of humic substances to bind free radicals in the system and to remove active radical species from the reaction sphere, according to the following reaction [ 34 ]: HA–H + DPPH•→HA• + DPPH–H …”

Section: Resultsmentioning

confidence: 99%

“…Although antiradical and antioxidant activities of some native humic substances have been reported previously [ 28 , 32 , 33 , 34 ], there is no information regarding specific HAs isolated from peat. Because peat could represent an important source of HAs for the pharmaceutical industry, characterization and standardization of their physical and chemical parameters is necessary [ 35 ], especially since no clear relationships have been reported between the pharmacological activities of peat-derived HAs and their humification degree, molecular size distribution, or stable-free radical content [ 36 ].…”

Section: Introductionmentioning

confidence: 99%

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Physicochemical Characterization and Antioxidant Activity of Humic Acids Isolated from Peat of Various Origins

et al. 2018

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Although humic acids (HAs) from peat exhibit various therapeutic properties, there is little information available concerning their physicochemical and antioxidant properties. To address this issue, nine different types of peat, including oligotrophic, mesotrophic, and minerotrophic peat samples, were used for isolation of HA fractions by basic (HAb) and pyrophosphate (HAp) extractions. Physical parameters of the HAs were analyzed by UV-Vis, fluorescent, infrared (IR), and electron paramagnetic resonance (EPR) spectroscopy. Average Mr of the fractions ranged from 17.2 to 39.7 kDa, while their humification index (HIX) varied from 0.49 to 1.21. HAp fractions had a higher content of aromatic structures compared to HAb fractions. Moreover, HAp fractions had a significantly higher content of phenolic OH groups (3.6 ± 0.5 mmol/g) versus HAb (3.1 ± 0.5 mmol/g). All HA fractions exhibited antioxidant activity in radical scavenging and electrochemical assays, and their EPR signal had a single line with g = 2.0035, which is consistent with semiquinone type radicals. Furthermore, the HIX was found to be important in determining the number of semiquinone-type free radicals in the HA structures. Overall, these data provide a molecular basis to explain at least part of the beneficial therapeutic properties of peat-derived HAs.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Physicochemical Characterization and Antioxidant Activity of Humic Acids Isolated from Peat of Various Origins

et al. 2018

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“…Moreover, they exhibit a strong attitude toward Reactive Oxygen Species (ROS) quenching, due to their intrinsic paramagnetic properties, resulting as effective antioxidant agents. The red-ox behavior of humic substances is strongly related to the phenol/quinone moieties in their complex supramolecular structures [14,15]. However, their rapid conformational dynamics and, hence, fast reactivity in water environments render humic substances of poor use for several applications in aqueous media [7,16].…”

Section: Introductionmentioning

confidence: 99%

“…Silica has been identified as an ideal support for this method, due to its strong hydrophilicity, acknowledged biocompatibility, as well as tunable size, shape, porosity and surface chemistry [21,24]. The immobilization of HA onto silica appears as a valid approach to exploit the large reactive potential of these moieties for several technological solutions spanning separation chromatography [25], water remediation [9,[26][27][28] and antioxidant products [14,15].…”

Section: Introductionmentioning

confidence: 99%

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

et al. 2020

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Humic acids (HA) exhibit fascinating multifunctional features, yet degradation phenomena as well as poor stability in aqueous environments strongly limit their use. Inorganic nanoparticles are emerging as a powerful interface for the development of robust HA bio-hybrid materials with enhanced chemical stability and tunable properties. Hybrid organic-inorganic SiO 2 /HA nanostructures were synthesized via an in-situ sol-gel route, exploiting both physical entrapment and chemical coupling. The latter was achieved through amide bond formation between carboxyl groups of HA and the amino group of 3-aminopropyltriethoxysilane (APTS), as confirmed by Fourier-Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Monodisperse hybrid nanoparticles about 90 nm in diameter were obtained in both cases, yet Electron Paramagnetic Resonance (EPR) spectroscopy highlighted the different supramolecular organization of HA. The altered HA conformation was reflected in different antioxidant properties of the conjugated nanoparticles that, however, resulted in being higher than for pure HA. Our findings proved the key role of both components in defining the morphology of the final system, as well as the efficacy of the ceramic component in templating the HA supramolecular organization and consequently tuning their functional features, thus defining a green strategy for bio-waste valorization.

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“…Humus and the products obtained from humus are used in agricultural and biomedical fields. It is possible to count anti-viral, anti-inflammatory, anti-oxidant, anti-tumor, anti-toxin among the most known activities of HA substances [2][3][4][5][6]. Many researchers have suggested that HA has the power to protect against cancers and cancer-causing viruses.…”

Section: Introductionmentioning

confidence: 99%

The Cytotoxic Effects of Humic Acid on Human Breast Cancer Cells

Aykaç

Becer

Okcanoğlu

et al. 2018

The 2nd International Cell Death Research Congress

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Breast cancer is the most common cancer among women and in order to create alternative treatments different types of in vivo and in vitro studies have used various plant-based therapeutic agents. Humic acid (HA) induces apoptosis and has various pharmacological properties including anti-inflammatory and anti-proliferative effects. In our study, we examined the cytotoxic effects of HA at concentrations of 5, 10, 20, 50 and 100 μg/mL in human breast adenocarcinoma MCF-7 cell line for 24 and 48 h. By using MTT method, it has been found out that HA 100 g/mL had cytotoxic effect on human breast adenocarcinoma MCF-7 cell line at both 24 and 48 h; also found out that the effective dose of HA at the same time (24 and 48 h) was 50 μg/mL. The results of our study will shed light on the development of alternative therapeutic approaches in the treatment of cancer by evaluating the cytotoxic effect of HA.

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Antioxidant activity of humic acids in radical-chain oxidation processes

Cited by 19 publications

References 3 publications

Physicochemical Characterization and Antioxidant Activity of Humic Acids Isolated from Peat of Various Origins

Physicochemical Characterization and Antioxidant Activity of Humic Acids Isolated from Peat of Various Origins

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

The Cytotoxic Effects of Humic Acid on Human Breast Cancer Cells

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