To date, simple and operative electrochemical methods are widely used to study antioxidant properties of various biological objects. One of them is the amperometric method, which is used in various...

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.

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.

Phosphatidylcholine (PC) liposomes are widely used as models of living cell biomembranes for studying various biochemical processes proceeding in them, in particular, lipid peroxidation (LPO) and effects of different substances on this process. In this work, dynamic light scattering has been employed to study the dynamics of variations in the sizes and ζ-potentials of soybean PC liposomes during their oxidation at 37°С initiated by 2,2'-azobis(amidinopropane) dihydrochloride. The effects of α-linoleic acid and carnation essential oil incorprated into the liposomes, as well as the encapsulation of the liposomes with sodium caseinate, on these parameters have been investigated. It has been found that the average size of PC liposomes increases by 6–7% in the course of oxidation; however, no correlation between their sizes and accumulation of LPO products has been revealed. By the end of the oxidation, the absolute value of the ζ potential increases by three times. The inclusion of α-linoleic acid into liposomes substantially changes the dynamics of variations in their sizes and ζ potential. The presence of carnation essential oil in liposomes decreases the accumulation of conjugated dienes during the oxidation and stabilizes the sizes and ζ-potentials by the end of oxidation for both original liposomes and liposomes containing α-linoleic acid. Encapsulation of liposomes with sodium caseinate stabilizes the sizes and ζ-potentials of complex structures formed in the course of oxidation.

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.