Biochemical, physiological, and anatomical features of salt tolerance of Sedum dendroideum Moc. Sessé ex DC species with obligate CAM photosynthesis were studied at moderate (300 mM NaCl) and high (500 mM NaCl) salinity. Differences in the response of plants to different levels of salinity were revealed. Under moderate salinity, an increase in photosynthetic CAM metabolism was observed, which was accompanied by a significant increase in night-time acidification of cell sap in tissues, the content of PEP carboxylase and proline, and activation of cyclic electron transport around PS I and superoxide dismutase activity. Significant anatomical changes in mesophyll cells of leaf and stem were revealed: compression of vascular bundles, granularity of the cytoplasm, plasmolysis of leaf mesophyll parenchyma cells and their displacement towards the vascular bundle. A number of parameters changed depending on the level of salinity and these changings were more pronounced at high salinity. Significant reduction in leaf biomass, accumulation of sodium ions, increased plasmolysis of leaf cells, and an increase in the volume of water-bearing parenchyma cells of the stem, accompanied by the destruction of their cell walls (lysis) was observed at high salinity. Oxidative stress was observed only under high salinity but was mild, probably due to a significant increase in peroxidase activity, the content of fatty acid esters and phenolic compounds, namely flavans. Thus, an increase in the photosynthetic CAM pathway was observed only under moderate salinity. Under high salinity, the decisive factor in the adaptation process was the activation of the antioxidant system. Implementation of S. dendroideum at different levels of salinity and various adaptation mechanisms, as well as regulation by external factors of the degree of manifestation of the obligate CAM pathway, is discussed.

A modification of the method for determining the total content of phenolic compounds in plant tissue extracts with the Folin-Denis reagent and the Folin-Ciocalteu reagent has been carried out, allowing to establish the correspondence of the results obtained when using them. The method using the Folin-Denis reagent is adapted for conducting determinations in microvolumes. For the method using the Folin-Ciocalteu reagent, the concentration of the latter (0.4 N, a 5-fold dilution of the standard reagent) and the composition of the reaction mixture were selected, using which the optical densities of the reduction products of the Folin-Denis and Folin-Ciocalteu reagents containing polyphenols in ethanol extracts from wheat, buckwheat and calus tissue of tea were almost the same. The absorption spectra of the reduction products of these reagents by gallic acid, rutin, (-)-epicatechin, as well as ethanol extracts from wheat, buckwheat, and tea calus tissue, were located in the same region (680–770 nm) and had similar characteristics. Calibration graphs of the dependence of the optical density of solutions on the concentration of standard substances (gallic acid, (-)-epicatechin, rutin), constructed using the Folin-Denis and Folin-Ciocalteu reagents, had a linear character within the concentration range of 10–100 μg/ml and practically coincided. The results of determining the content of phenolic compounds in ethanol extracts of plants, differing in their ability to accumulate, showed very similar and statistically significant values when using these two reagents.

Various species of the genus Aloe which there are in the world more than 500 are considered as important sources of biologically active substances and attract an attention of researchers by numerous manifestations of their biological properties. The most studied and used Aloe species are A. arborescens and A. vera, however some other species show not smaller biological activity, in particular antioxidant, than made mention. In the present work on model of the initiated oxidation of phosphatidylcholine liposomes comparison of the antioxidant activity (AOA) of leaves extracts of A. arborescens, A. pillansii, A. squarrosa and also the total content of their phenolic compounds was carried out. It is established that A. pillansii extract has approximately by 12 times higher AOA, than A. arborescens extract, and by 4 times, than A. squarrosa. The measured values of the total phenolic compounds content showed considerably smaller difference between these extracts. It can demonstrate existence in A. pillansii leaves of more difficult antioxidant profile, than in A. arborescens, and higher concentration of active phenolic metabolites. Results of this work allow recommending A. pillansii for more depth studies of its different biological activities.

Numerous species of the genus Aloe have attracted the attention of researchers because of their different biological benefits and their capacity to act as antioxidants. This paper presents a comparative study of the kinetics of the inhibitory effect of ethanol extracts of five species of Aloe , which was made using a model system of the oxidation of phosphatidylcholine liposomes. It was found that plant extracts of A. marlothii and A. congolensis have higher antioxidant activities (by a factor of 13 and 10, respectively) than the best known Aloe species: A. arborescens and A. vera . The total phenolic content values of A. marlothii and A. congolensis are higher than those of A. arborescens and A. vera but to a lesser degree (by a factor of 5–6) than antioxidant activity. This may indicate the presence of very active phenolic antioxidants in A. Marlothii and A. congolensis . An analysis of the influence of extracts introduced into liposomes on liposome size showed that the most active extracts of A. marlothii , A. congolensis , and A. pillansii reduce the average liposome size compared to pure liposomes, and extracts with weaker antioxidant activity increase it, which is probably due to changes in the lipid structure of liposomes by the components of extracts. Based on the results we obtained, A. marlothii , A. congolensis , and A. pillansii are suitable for studying other types of their biological activity that might contribute to new drug development.

Исследовали накопление различных фенольных соединений в листьях Anacampseros filamentosa (Haw.) Sims и ее красноокрашенной формы. Более высокое содержание фенольных соединений, в том числе флавоноидов и антоцианов, характерно для красноокрашенной A. filamentosa (Haw.) f. rubra. Investigated the accumulation of various phenolic compounds in the leaves of Anacampseros filamentosa (Haw.) Sims and its red-colored form. In the red leaves of A. filamentosa (Haw.) f. rubra content of phenolic compounds, including flavonoids and anthocyanins, was high.

Nowadays, a search for sources of the most biologically active antioxidant compounds among various herbs is an urgent problem. In this connection, several succulent plants from the Aloe genus are of special interest, because their preparations are widely used in domestic medicine. In this study, we measured the antioxidant activity (AOA) of an alcoholic extract of leaves of 15 Aloe species by amperometric and chemiluminescent methods and performed a comparative analysis of the results. We observed a considerable difference between the AOA values for the several Aloe species and explained this fact. The most active antioxidant among the samples proved to be the A. pillansii representative of the Aloe genus. Both methods demonstrated that the extracts from leaves of this Aloe species exhibited the high AOA. The A. broomii and A. spinosissima also had rather high AOA along with the A. pillansii and A. arborescens . The newly discovered Aloe species could be as promising a source of biologically active compounds as the traditionally used A. arborescens and A. vera .

A study of the biological, including the antioxidant, activity of various medicinal plants with the aim of searching for the most active sources of biologically active compounds among them is, at present, of interest. In the present work, a comparative analysis of the antioxidant activity of juices from 14 Kalanchoe species, measured by the ammetric, voltammetric, and chemiluminescence methods has been performed. Among the samples examined, two members of the Kalanchoe genus were shown to have the highest antioxidant activity: Kalanchoe scapigera and K. rhombopilosa . They may appear to be richer sources of biologically active compounds compared with the currently used Kalanchoe species.

One of actual problems of modern pharmacology is creation of new medicines on the basis of vegetable raw materials. In this plan some succulents present a great interest in particular some kinds of the genus Kalanchoe, such as Kalanchoe pinnata (K.pinnata) and Kalanchoe Daigremontiana (K.daigremontiana). Their leaves contain useful mineral salts, organic acids and the numerous phenolic compounds (PC). Education and accumulation of these PC depends on genetic features of a plant and numerous factors of environment. Besides, these representatives of a secondary metabolism cause biological, including antioxidant activity (AOA) of this or that species of a plant, that is ability its component to inhibit oxidizing free radical processes. Use of modern methods of antioxidant properties research for plant extracts or juice of this or that plant allow to study and reveal their medicinal value at higher level.In the present work the comparative analysis of measurement results of the total phenols content and their activity in leave juice of various kinds of Kalanchoe (Kalanchoe L.) is carried out by ammetric and chemiluminescence methods for the purpose of identification among them the most active producers of phenol metabolites. Objects of research were juice samples of 34 kinds of the genus Kalanchoe, grown up in a succulent collection in Timiryazev Institute of plant physiology RAS (Moscow, Russia). Among the studied samples two most active from the point of view of their antioxidant properties Kalanchoe kinds: K.scapigera and K.rhombopilosa are revealed. Both methods show considerably higher values of the phenol metabolite content in leave juice of these plants and their AOA in comparison with K.pinnata and K.daigremontiana. For possible expansion for use of specified types of Kalanchoe as sources of biologically active compounds, additional researches of biochemical structure, antibacterial, antimicrobic and other properties of these plant components is necessary. Probably, they will appear more perspective for their use in pharmacy and medicine.

A tolerance to paraquat (PQ) of plants and cell cultures of Arabidopsis thaliana mutants, nfz18 and nfz24, obtained by chemical mutagenesis and selected by their tolerance to norflurason was demonstrated. This tolerance to PQ was manifested in less active peroxidation of lipids (POL), which was assessed by the content of thiobarbituric acid-reactive substances, and in a less degree of plant and callus damages, which was accompanied by a higher activity of superoxide dismutase and other antioxidant enzymes. A capability of norflurason-tolerant mutants to cross-adaptation toward PQ and activation of antioxidant enzymes indicate a genetically determined activation of the antioxidant systems, resulting in improved mutant tolerance to these inducers of oxidative stress. The nfz24 mutant was much more sensitive to hypothermia than wild-type plants and nfz18 mutants, which was expressed in a higher level of POL in plants and calluses and in a more rapid decrease in the suspension cell viability of this mutant. A similarity in the responses of plants and derived heterotrophic cultures to PQ and hypothermia indicates that, in these A. thaliana mutants, adaptation to these types of stresses occurs mainly at the cellular level. Possible reasons of increased sensitivity to hypothermia of the nfz24 mutant, which was more tolerant to the inducers of oxidative stress, PQ and norflurason, are discussed.

Effect of UV-B rays (280–320 nm) on photosynthetic electron transport and production of phenolic compounds in tea (Camellia sinensis L.) callus culture grown in white light was investigated. When white light was supplemented with UV radiation, the culture growth was retarded and morphological characteristics were modified. These conditions promoted the formation of chlorophyll-bearing cells and altered the ability of cultured cells to accumulate phenolic compounds, including flavans specific to Camellia sinensis. By the end of the culturing cycle (on the 45th day), the total content of phenolic compounds in the culture grown under supplementary UV irradiation was almost 1.5 times higher than in the control culture. The UV rays greatly stimulated photosystem II (PSII) activity in phototrophic cells of the callus culture, which was indicated by a large increase in the ratio of variable chlorophyll fluorescence to maximal fluorescence. This ratio was as low as 0.19 in cells cultured in white light and increased to 0.53 in the cell culture grown under white and UV light. The kinetics of dark relaxation of chlorophyll variable fluorescence, related to reoxidation of PSII primary acceptor, contained either two or three components, depending on the absence or presence of UV radiation, respectively. An artificial electron acceptor of PSI, methyl viologen modified the kinetics of dark decay of chlorophyll variable fluorescence in a characteristic manner, implying that photosynthetic electron transport was mediated by PSI and PSII in both treatments (culturing in white light with and without UV-B). It is concluded that stimulatory effect of UV rays on the parameters examined in phototrophic regions of Camellia tissue culture is determined by photoexcitation of a regulatory pigment that absorbs quanta in blue and long-wave UV spectral regions.