Anti-fatigue effects of small-molecule oligopeptides isolated from Panax quinquefolium L. in mice
American ginseng (Panax quinquefolium L.) was reported to have extensive biological activities and pharmaceutical properties. In most of the studies, the anti-fatigue effects of American ginseng are attributed to ginsenoside, and in only a few studies, they have been attributed to oligopeptides. Therefore, the aim of this study was to observe the anti-fatigue effects of small-molecule oligopeptides isolated from Panax quinquefolium L. (QOPs) in mice. At first, mice chosen for the study were randomly divided into four experimental groups; each group of mice was further divided into five subgroups: vehicle control group, whey protein group (450 mg per kg BW), and three groups of QOPs at different doses (225 mg per kg BW, 450 mg per kg BW, and 900 mg per kg BW). Test substances were given by gavage once a day for 30 days. QOPs can significantly prolong the forced swimming time, decrease the serum urea nitrogen (SUN) and blood lactate (BLA) levels, and increase the lactate dehydrogenase (LDH) activity and hepatic glycogen content. QOPs also markedly enhanced the superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity and attenuated the malondialdehyde (MDA) levels. Notably, QOPs enhanced the activity of succinate dehydrogenase (SDH), Na+-K+-ATPase, and Ca2+-Mg2+-ATPase and increased the mRNA expression of nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (TFAM) and the mitochondrial DNA (mtDNA) content in skeletal muscles. These results indicate that treatment with QOPs induces anti-fatigue effects, which may be due to the inhibition of oxidative stress and the improvement of mitochondrial function in skeletal muscles. QOPs can be used as a novel natural agent for relieving physical fatigue.