Effects of natural polyphenols resveratrol, dihydromyricetin, pinosylvin, epigallocatechin, myricetin, and dihydroquercetin on the peroxide generation in rat liver mitochondria in the conditions of toxic damage induced by hepatotrophic poison thiacetoamide were studied. In liver mitochondria of rats with toxic hepatitis all polyphenols at a concentration of 10 mu M served as antioxidants and lowered the signal of the fluorescent probe Amplex Red with the efficiency decreasing in the following order: resveratrol > myricetin > dihydroquercetin > pinosylvin > dihydromyricetin. In liver mitochondria isolated from the control animals the polyphenols studied affected the generation of free radicals insignificantly. In the conditions of the nonspecific Ca2+-dependent permeabilization of mitochondrial membrane in the presence of Ca2+ ions and inorganic phosphate, the polyphenols exhibited an antioxidant activity and notably decreased the peroxide generation rate in the mitochondria of the control animals. Mitochondria isolated from the liver of the animals with induced pathology showed more than a 20-fold increase in the peroxide level, which significantly decreased in the presence of polyphenols; most effective among the polyphenols were dihydroquercetin, pinosylvin, and dihydromyricetin, which decreased the level of peroxide production 7-13-fold. The presented data bring the clarity to the ambivalent effect of the polyphenols in living model systems and suggest that under the conditions of cell pathology natural polyphenols should produce a powerful antioxidant effect, while under physiological conditions the polyphenols can exert a neutral or mild pro-oxidant effect. The obtained data may be applied to the development of new potential pharmacological natural preparations to treat common diseases based on mitochondrial pathologies.

The effect of stilbene polyphenols (resveratrol and pinosilvin) and flavonoids (dihydromyricetin, epigallocatechin, and dihydroquercetin) on producing the reactive oxygen species (ROS) due to cell respiration using the isolated mitochondria of the fungus Dipodascus (Endomyces) magnusii was studied. It was shown that the inhibition of the ROS generation with stilbenes is related to both the oxygen consumption inhibition and their antioxidant properties. The degree of manifestation of polyphenol antioxidant properties depended on the number of hydroxyl groups in a polyphenol molecule. Of the flavonoids tested, dihydromyricetin was most active in reducing the ROS generation, but its inhibitory effect on oxygen consumption by mitochondria was significantly lower as compared to that of the stilbenes. The data obtained show that the mechanism of reducing the ROS generation with polyphenols is associated with both the respiratory inhibition and their antioxidant properties.

First, the effects of the biologically active polyphenols resveratrol and dihydroquercetin (DHQ) on morpho-physiological parameters and the antioxidant status of polyextremophilic yeast Yarrowia lipolytica at optimal and elevated temperatures were studied. Cultivation in the presence of 30 μM resveratrol at the optimal temperature caused a twofold increase in superoxide dismutase activity. It was shown that cultivation at a high temperature and high DHQ concentration stimulated a decrease in the alternate respiration level. High resveratrol concentrations and low dihydroquercetin concentrations were shown to have an inhibitory effect on the survival rate of Y. lipolytica yeast cells, while no visible inhibition effect of yeast growth was recorded at the optimal growth temperature. Polyphenols were shown to have a moderate stimulatory effect on the oxygen absorption rate by yeast cells.

Неалкогольная жировая дисфункция печени сопровождает целый ряд заболеваний (диабет, ожирение, кардиоваскулярные болезни), а также может развиваться под действием лекарственных препаратов или токсических соединений. Актуальным направлением современной медицины является поиск эффективных средств профилактики и лечения жирового гепатоза. Целью работы было исследовать действие некоторых биологически активных природных полифенолов — стильбенов ресвератрола и пиносильвина, а также дигидрофлавонола дигидромирицетина — на функциональное состояние и гистологическую картину печени. В модели токсического гепатита, вызываемого введением гепатотоксиканта тиоацетамида, самцам крыс линии Wistar внутрижелудочно ежедневно вводили зондом эффективные дозы полифенолов на фоне добавления тиоацетамида к питьевой воде в концентрации 0,05%. Все исследованные полифенолы способствовали стабилизации веса крыс и двухкратному достоверному (p < 0,05) снижению уровня прямого билирубина в сыворотке крови животных, получавших тиоацетамид. Гистологическое исследование печени подтвердило замедление воспалительных процессов и уменьшение кровоизлияний у животных, получавших полифенолы на фоне продолжающегося введения тиоацетамида в течение 30 дней. На основании полученных данных можно сделать выводы, что природные полифенолы класса дигидрофлавонолов (дигидромирицетин) и стильбенов (ресвератрол и пиносильвин) оказывают положительное воздействие на функции печени в модели экспериментального токсического гепатоза; исследованные полифенолы можно рассматривать в качестве потенциальных гепатопротекторов в составе комплексной терапии при заболеваниях печени.

Alterations in the concentrations of cell cytosol carbohydrates of polyextremophilic yeasts Yarrowia lipolytica under stresses of diverse nature were observed. Under pH stress, mannitol was the main storage carbohydrate (up to 89% of the total cytosol carbohydrates), while arabitol, glucose, and inositol were present in insignificant amounts (3 to 6%). Experiments with inhibition of de novo mannitol synthesis by bis(p-nitrophenyl) disulfide revealed that the cytoprotective effect of mannitol was most noticeable in the cells grown under acidic conditions (pH 4.0), while the role of catalase and superoxide dismutase, the enzymes of the first line of antioxidant protection, increased under alkaline conditions (pH 9.0). The constitutively high mannitol content in Y. lipolytica cells was hypothesized to be a part of the core mechanism of stress resistance in this yeast species.

In this study we investigated the activities of antioxidant enzymes (superoxide dismutases (SODs) and catalases (CATs)) and the ROS level in cells of Yarrowia lipolytica yeasts grown in a medium with different pH values (4.5, 5.5 and 9.0). It was shown that an increase in the cellular ROS level took place under both acid and alkaline conditions. The growth under extreme conditions was accompanied by a significant increase of SOD activity (by 2.5 times in the acid medium and by 4 times in the alkaline medium), but catalase activity did not change. A study of the electrophoretic profile of catalases showed the presence of three isoforms differing in inhibitor resistance. The electrophoretic profiles of SODs and their inhibitory analysis revealed there are two other isoforms, probably of mitochondrial origin, in addition to Cu and Zn SOD. The role of SOD in pH-adaptation of extremophilic Y lipolytica yeasts is discussed.

Исследованы изменения активности ферментов антиоксидантной защиты (супероксиддисмутаз, СОД, и каталаз), а также уровня активных форм кислорода в дрожжевых клетках Yarrowia lipolytica при выращивании на средах с различными значениями рН (4.5, 5.5 и 9.0). Показано, что увеличение уровня активных форм кислорода в клетках происходило как в кислых, так и в щелочных условиях. Рост клеток в экстремальных условиях сопровождался значительным увеличением активности СОД (в 2.5 раза в кислых и в 4 раза в щелочных условиях), при этом активность каталазы не изменялась. Изучение электрофоретического профиля каталаз показало присутствие трех изоформ, различающихся по устойчивости к ингибиторам этих ферментов. Электрофоретический профиль СОД и ингибиторный анализ выявил, наряду с присутствием Cu, Zn-СОД, наличие двух других форм, предположительно митохондриального происхождения. Обсуждается роль СОД в рН-адаптации экстремофильных дрожжей Y. lipolytica.