Lifespan extension and delay of age-related functional decline caused by Rhodiola rosea depends on dietary macronutrient balance

BACKGROUND: This study was conducted to evaluate the effects of rhizome powder from the herb Rhodiola rosea, a traditional Western Ukraine medicinal adaptogen, on lifespan and age-related physiological functions of the fruit fly Drosophila melanogaster. RESULTS: Flies fed food supplemented with 5.0 mg/ml and 10.0 mg/ml of R. rosea rhizome powder had a 14% to 17% higher median lifespan, whereas at 30.0 mg/ml lifespan was decreased by 9% to 12%. The preparation did not decrease fly fecundity. The effect of R. rosea supplement on lifespan was dependent on diet composition. Lifespan extension by 15% to 21% was observed only for diets with protein-to-carbohydrate ratios less than 1. Lifespan extension was also dependent on total concentration of macronutrients. Thus, for the diet with 15% yeast and 15% sucrose there was no lifespan extension, while for the diet with protein-to-carbohydrate ratio 20:1 R. rosea decreased lifespan by about 10%. Flies fed Rhodiola preparation were physically more active, less sensitive to the redox-cycling compound menadione and had a longer time of heat coma onset compared with controls. Positive effects of Rhodiola rhizome on stress resistance and locomotor activity were highest at the ‘middle age’. CONCLUSIONS: The present data show that long-term food supplementation with R. rosea rhizome not only increases D. melanogaster lifespan, but also delays age-related decline of physical activity and increases stress resistance, what depends on protein-to-carbohydrate ratio of the diet.