Modern medicine strives to prevent age-related diseases. Oxidative stress is associated with development and progression of various diseases. Reactive oxygen species are part of vital physiological processes. High levels of reactive oxygen lead to stress and pathology whereas low ones are associated with healthy physiology. Plant-derived adaptogens demonstrate good results in stress tolerance and homeostasis. Plant materials are a pharmacologically optimal source of chemical compounds to treat various diseases, including those caused by oxidative stress. The research featured biologically active substances isolated from extracts of callus, suspension, and root cultures of medicinal plants. Baicalin and trans-cinnamic acid were obtained from Scutellaria baicalensis while ursolic acid came from Thymus vulgaris. The biologically active substances were tested for neuroprotective properties, as well as for the impact on the expression of SOD-3 and HSP-16.2. Caenorhabditis elegans served as a model to study the accumulation of carbonylated proteins and lipofuscin. The neuroprotective activity of all tested substances decreased as their concentration fell from 200 to 10 μmol/L. C. elegans proved more resistant to thermal stress if pretreated with the biologically active substances. In response to thermal stress, nematodes expressed SOD-3 more actively than HSP-16.2. At 100 μmol/L, the biologically active substances could reduce the level of carbonylated proteins. Ursolic acid was especially effective against protein carbonylation and lipofuscin accumulation in all concentrations. Baicalin, trans-cinnamic acid, and ursolic acid made it possible to reduce oxidative and thermal stress, thus demonstrating good prospects for further studies as part of adaptogenic prepa rations.