Antifatigue Effects of the Aqueous Extracts of Myrtle Berries, Apple and Clove: An Animal Study

Background: Fatigue is one of the most prevalent symptoms, increasing worldwide with no specific medication for fatigue. Iranian traditional medicine (ITM), or Persian medicine, is a reliable source for discovering natural medicine for diseases and their symptoms. Myrtus communis L. (Myrtle), Malus domestica Borkh. (Apple), and Syzygium aromaticum (L.) Merr. & L. M. Perry (Clove) have been utilized as brain and heart tonics in ITM. Based on ITM, cardiac tonics decrease fatigue by enhancing heart function and increasing blood flow to tissues. These plants, particularly myrtle berries, have been utilized as potent enlivening agents that reduce mental fatigue. Objectives: This study aims to investigate the effects of aqueous extracts of these plants on weight-loaded forced swimming (WLFS) tests and three doses of aqueous myrtle extract in an animal model of chronic sleep deprivation-induced fatigue. Methods: Five groups of rats (n = 6) were evaluated: sham, control, apple-treated, clove-treated, and myrtle-treated groups. After 28 days of treatment, the WLFS test was performed, and swimming time was recorded. Subsequently, central fatigue was induced in rats by chronic sleep deprivation for 21 days. Five groups of rats (n = 6) were evaluated: sham, control (sleep-deprived, which received water), and three sleep-deprived + treatment groups, which received aqueous myrtle extract (350, 700, and 1000 mg/kg). An open field test on the 20th day and a WLFS test on the 21st day were performed. Results: The myrtle berries significantly increased glucose, reduced lactate dehydrogenase (LDH) levels, and enhanced swimming time. Fatigue caused by chronic sleep deprivation increased malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and LDH while decreased superoxide dismutase (SOD), glucose, and swimming time. In all treatment groups, SOD levels and swimming time were increased, whereas MDA, IL-1β, and TNF-α levels were decreased significantly. Only the 1000 mg/kg dose significantly reduced LDH levels (P < 0.001). The treatment significantly improved the velocity and the total distance moved in the open-field test. Conclusions: According to the results, the myrtle berries reduced fatigue in two animal models, probably due to its phenolic compounds, flavonoids, and polysaccharides.