| Summary: | Pollinators, the cornerstones of our terrestrial ecosystem, have been at the very core of our anxiety. This is because we can nowadays observe a dangerous decline in the number of insects. With the numbers of pollinators dramatically declining worldwide, the scientific community has been growing more and more concerned about the future of insects as fundamental elements of most terrestrial ecosystems. Trying to address this issue, we looked for substances that might increase bee resistance. To this end, we checked the effects of plant-based adaptogens on honeybees in laboratory tests and during field studies on 30 honeybee colonies during two seasons. In this study, we have tested extracts obtained from: <i>Eleutherococcus senticosus, Garcinia cambogia, Panax ginseng, Ginkgo biloba, Schisandra chinensis</i>, and <i>Camellia sinensis</i>. The 75% ethanol <i>E. senticosus</i> root extract proved to be the most effective, both as a cure and in the prophylaxis of nosemosis. Therefore, <i>Eleutherococcus senticosus</i>, and its active compounds, eleutherosides, are considered the most powerful adaptogens, in the pool of all extracts that were selected for screening, for supporting immunity and improving resistance of honeybees. The optimum effective concentration of 0.4 mg/mL <i>E. senticosus</i> extract responded to c.a. 5.76, 2.56 and 0.07 µg/mL of eleutheroside B, eleutheroside E and naringenin, respectively. The effect of <i>E. senticosus</i> extracts on honeybees involved a similar adaptogenic response as on other animals, including humans. In this research, we show for the first time such an adaptogenic impact on invertebrates, i.e., the effect on honeybees stressed by nosemosis. We additionally hypothesised that these adaptogenic properties were connected with eleutherosides—secondary metabolites found exclusively in the <i>Eleutherococcus</i> genus and undetected in other studied extracts. As was indicated in this study, eleutherosides are very stable chemically and can be found in extracts in similar amounts even after two years from extraction. Considering the role bees play in nature, we may conclude that demonstrating the adaptogenic properties which plant extracts have in insects is the most significant finding resulting from this research. This knowledge might bring to fruition numerous economic and ecological benefits.
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