Effects of Hypericum scabrum extract on learning and memory and oxidant/antioxidant status in rats fed a long-term high-fat diet

Abstract

A high-fat diet (HFD) causes deficits in learning and memory by increasing oxidative stress. Antioxidants are known to improve learning and memory. Since Hypericum scabrum (H. scabrum) extract is rich in antioxidants, the aim of this study was to investigate the effects of the administration of H. scabrum extract on passive avoidance learning (PAL), novel object recognition (NOR), and locomotor activity in male rats on a HFD. Fifty-four male Wistar rats (weighing 220 ± 10 g) were divided into the following six groups: (1) Control (standard diet), (2) Ext100 (standard diet supplemented with 100 mg/kg extract once/day), (3) Ext300 (standard diet supplemented with 300 mg/kg extract once/day), (4) HFD (high-fat diet), (5) HFD + Ext100, and (6) HFD + Ext300. Rats in these groups were maintained on their respective diets for 3 months. In the PAL test, the step-through latencies in the retention test (STLr) were significantly higher in the HFD + extract group than in the HFD group. The time spent in the dark compartment (TDC) was significantly lesser and the time spent in exploring the novel object was significantly greater in the HFD + extract group than in the HFD group. In the HFD-fed rats, the activity of catalase had significantly decreased, and level of malondialdehyde had significantly increased; H. scabrum extract administration significantly reversed these changes. In conclusion, these results suggested that the administration of H. scabrum extract and its strong antioxidant properties enhanced learning and memory and reversed the memory impairment induced by chronic HFD consumption.

Effects of Hypericum scabrum extract on dentate gyrus synaptic plasticity in high fat diet-fed rats

“…It has been indicated that, its extract possess flavonoids, such as quercetin [70]; flavonoids act as antioxidants [71]. In confirmation of our results, administration of H. scabrum Ext in rats was shown to improve learning and memory and possess antioxidant activity [27]. In accordance with this finding, Pintana et al [72] have shown that an HFD impairs learning and memory, and treatment with garlic extract restores these impairments in obese insulinresistant rats.…”

“…Fifty-four rats (weighing 220 ± 10 g) were divided into 6 groups (n = 9): (1) HFD group, given an HFD with 45% energy from fat; (2) HFD + Ext300 group, given an HFD supplemented with H. scabrum extract (300 mg/ kg); (3) HFD + Ext100 group, given an HFD supplemented with H. scabrum extract (100 mg/kg); (4) control group, given a normal diet with 10% energy from fat and received the saline through oral gavage once a day for 3 months; (5) H. scabrum 300 mg/kg (Ext300) group, given the standard diet supplemented with H. scabrum (300 mg/kg); (6) H. scabrum 100 mg/kg (Ext100) group, given the standard diet supplemented with H. scabrum (100 mg/kg). Rats received the extract through oral gavage once a day for 3 months [3,14,27]. The gavage was performed from 9:00 to 11:00 a.m. All experimental procedures were done under international standards of animal care approved by the Society for Neuroscience.…”

“…H. scabrum extract at doses of 100 and 300 mg/kg was given by gavage in the 2 groups that were taking normal diet and in the 2 groups that were taking HFD daily for 3 months. These doses were determined based on former studies [3,27].…”

“…Herbs possess some of the most potent natural antioxidants such as phenols, phenolic elements, or flavonoids [26]. Recent studies have indicated promising effects of herbal medicines in the treatment of various memory disorders [27][28][29]. These effects could correlate to their antioxidant and anti-inflammatory properties [30][31][32].…”

Effect of a hydro-alcoholic extract of Melissa officinalis on passive avoidance learning and memory

“…A subject rodent was located in the light chamber facing away from the guillotine door. After five seconds, the door was opened, and following the entrance of rat to the dark chamber, the door was closed, and an electrical shock (50-Hz square wave, one mA for 1.5 seconds) was induced (24)(25)(26). Afterward, 30 seconds later the animal was delivered to the cage.…”