Extracts from Eleutherococcus senticosus (Rupr. et Maxim.) Maxim. Roots: A New Hope Against Honeybee Death Caused by Nosemosis

Abstract

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: Eleutherococcus senticosus, Garcinia cambogia, Panax ginseng, Ginkgo biloba, Schisandra chinensis, and Camellia sinensis. The 75% ethanol E. senticosus root extract proved to be the most effective, both as a cure and in the prophylaxis of nosemosis. Therefore, Eleutherococcus senticosus, 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 E. senticosus 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 E. senticosus 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 Eleutherococcus 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.

Keywords: Apis mellifera; Camellia sinensis; Eleutherococcus senticosus; Garcinia cambogia; Ginkgo biloba; Panax ginseng; Schisandra chinensis; adaptogenic herbs; eleutherosides; fumagillin; honeybee; insectageddon.

Figure 1

Results of cage tests: Screening of commercial plant extracts. Data illustrated honeybee lifespan, food consumption and nosemosis level in all three variants of experiments conducted, i.e., (A) uninfected honeybees, (B) treatment of nosemosis and (C) prevention of nosemosis were compared. Lowercase letters (a,b,c) indicate significant differences between the group fed pure sucrose syrup without extracts (SS) and the groups fed with additions of extracts (at least p ≤ 0.005 for the honeybee lifespan and nosemosis level, and p ≤ 0.05 for food consumption) (analysis of variance (ANOVA), Tukey test). Error bars denote a confidence interval (CI). Feeding groups (acronyms are defined in Supplementary Materials Table S1): (SS—sucrose syrup) control, pure sucrose syrup without extracts, (ESa) sucrose syrup supplemented with 0.2 mg/mL of commercial extracts of E. senticosus, (ESb) sucrose syrup supplemented with 1 mg/mL of commercial extracts of E. senticosus, (GGa) sucrose syrup supplemented with 0.2 mg/mL of commercial extracts of G. gummi-gutta, (GGb) sucrose syrup supplemented with 1 mg/mL of commercial extracts of G. gummi-gutta, (PGa) sucrose syrup supplemented with 0.2 mg/mL of commercial extracts of P. ginseng, (PGb) sucrose syrup supplemented with 1 mg/mL of commercial extracts of P. ginseng, (SCa) sucrose syrup supplemented with 0.2 mg/mL of commercial extracts of S. chinensis, (SCb) sucrose syrup supplemented with 1 mg/mL of commercial extracts of S. chinensis, (CSa) sucrose syrup supplemented with 0.2 mg/mL of commercial extracts of C. sinensis, (CSb) sucrose syrup supplemented with 1 mg/mL of commercial extracts of C. sinensis, (GBa) sucrose syrup supplemented with 0.2 mg/mL of commercial extracts of G. biloba, (GBb) sucrose syrup supplemented with 1 mg/mL of commercial extracts of G. biloba, and (Fum) fumagillin as a positive control in the treatment of nosemosis.

Figure 2

Results of cage tests: Screening for the best method of obtaining the Eleutherococcus extract. Data illustrated honeybee lifespan, food consumption and levels of nosemosis in all three variants of experiments conducted, i.e., (A) uninfected honeybees, (B) treatment of nosemosis and (C) prevention of nosemosis were compared. Lowercase letters (a,b,c) indicate significant differences between the group fed pure sucrose syrup without extracts (SS) and the groups fed with additions of extracts (at least p ≤ 0.05 for the honeybee lifespan, p ≤ 0.01 for food consumption and p ≤ 0.005 for level of nosemosis) (ANOVA, Tukey test). Error bars denote a confidence interval (CI). Laboratory extracts of E. senticosus (ES) and E. henryi (EH) were obtained using three different methods (water, W, chloroform, Ch, and ethanol, Et, extraction) from these plants’ roots and fruits (Table 2). 14 feeding groups (acronyms are defined in Supplementary Materials Table S2), i.e., (1) SS (control, pure sucrose syrup), (2) ESrW, (3) ESrCh, (4) ESrEt, (5) ESfW, (6) ESfCh, (7) ESfEt, (8) EHrW, (9) EHrCh, (10) EHrEt, (11) EHfW, (12) EHfCh, (13) EHfEt, (14) Fum (positive control in the treatment of nosemosis, fumagillin). All pure laboratory extracts were added in the concentration of 0.4 mg/mL to compare three different methods of obtaining extracts.

Figure 3

Results of cage tests: Screening for the best Eleutherococcus dose. Data illustrated honeybee lifespan, food consumption and the level of nosemosis in all three variants of conducted experiments, i.e., (A) uninfected honeybees, (B) treatment of nosemosis and (C) prevention of nosemosis were compared. Lowercase letters (a,b,c) indicate significant differences between the group fed with pure sucrose syrup without extracts (SS) and the groups fed with additions of extracts (at least p ≤ 0.05 for the honeybee lifespan, p ≤ 0.05 for food consumption and p ≤ 0.01 for level of nosemosis) (ANOVA, Tukey test). Error bars denote a confidence interval (CI). Feeding groups: E. senticosus ethanol root extract was added to the sucrose solution to the final concentrations of 0.05 mg/mL, 0.2 mg/mL, 0.4 mg/mL, 0.9 mg/mL and 1.5 mg/mL. Uninfected and Nosema-infected honeybees from A, B and C variants were divided into 14 feeding groups (acronyms are defined in Supplementary Materials Table S3): (1. SS) control, pure sucrose syrup without extracts, (2. ES0.05) sucrose syrup supplemented with 0.05 mg/mL E. senticosus extract, (3. ES0.2) sucrose syrup supplemented with 0.2 mg/mL E. senticosus extract, (4. ES0.4) sucrose syrup supplemented with 0.4 mg/mL E. senticosus extract, (5. ES0.9) sucrose syrup supplemented with 0.09 mg/mL E. senticosus extract, (6. ES1.5) sucrose syrup supplemented with 1.5 mg/mL E. senticosus extract, (7. Fum) fumagillin, positive control in the treatment of nosemosis.

Figure 4

Results of additional tests: Field tests. Data illustrated winter debris and average levels of nosemosis in honeybee colonies fed with pure sucrose solution without extraxts (F1 and F4 groups with uninfected and Nosema-infected colonies, respectively), with E. senticosus extract in the concentration of 0.4 mg/mL (F2 and F5 groups with uninfected and Nosema-infected colonies, respectively) and with E. senticosus extract in the concentration of 0.9 mg/mL (F3 and F6 groups with uninfected and Nosema-infected colonies, respectively). Error bars denote a confidence interval (CI). In each apiary, colonies were divided into 6 groups, i.e., (F1) 5 colonies as control, untreated group with healthy honeybees, (F2) 5 colonies with healthy honeybees fed with E. senticosus extract in the concentration of 0.4 mg/mL, (F3) 5 colonies with healthy honeybees fed with E. senticosus extract in the concentration of 0.9 mg/mL, (F4) 5 untreated colonies with Nosema-infected honeybees, (F5) 5 colonies with Nosema-infected honeybees fed with E. senticosus extract in the concentration of 0.4 mg/mL and (F6) 5 colonies with Nosema-infected honeybees fed with E. senticosus extract in the concentration of 0.9 mg/mL.

Figure 5

An exemplary chromatogram of the eleutheroside B, E and naringenin in the samples of freshly sourced extract.

Figure 6

The scheme of administered experiments analysing the effect of extracts on honeybees which were uninfected and infected with Nosema ceranae.