Abstract
- Background
Rosemary extract (RE) is widely recognized for its diverse biological activities, including potent antioxidant, cytoprotective, and cognition-improving properties, largely attributed to bioactive constituents such as carnosic acid. Aging is accompanied by progressive cognitive decline, heightened oxidative stress, and structural vulnerability within the hippocampal formation. Despite established neuroprotective benefits, the comparative dose-response efficacy of standardized rosemary extract on hippocampal function and redox balance remains critical to optimize therapeutic windows. This experimental study was designed to investigate and determine the optimal effective doses of RE containing 40% carnosic acid on spatial learning, memory retrieval, hippocampal neuronal survival, antioxidant enzyme activities, and lipid peroxidation in a middle-aged rat model.
- Methods
A rigorous controlled experimental in vivo study was conducted using thirty-two middle-aged male Wistar rats. Subjects were randomly assigned to receive daily oral administrations of either different standardized doses of rosemary extract (50, 100, or 200 mg/kg/day, standardized to 40% carnosic acid) or distilled water (control group) over a 12-week experimental intervention period. Comprehensive behavioral, histological, and biochemical assessments were systematically performed:
Cognitive & Behavioral Testing: Learning and spatial memory retrieval scores were evaluated using validated experimental paradigms.
Histological Evaluation: Hippocampal neuronal survival and structural integrity were examined.
Biochemical & Redox Profiling: Hippocampal tissues were harvested to quantify endogenous antioxidant enzyme activities—including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT)—alongside the measurement of lipid peroxidation levels via malondialdehyde (MDA) quantification.
Statistical evaluations were performed using one-way and two-way analysis of variance (ANOVA).
- Results
Administration of rosemary extract demonstrated distinct, dose-dependent neuroprotective and antioxidant improvements, with the intermediate dose exhibiting superior efficacy:
Memory Recovery: Treatment with RE at 100 mg/kg/day significantly recovered and improved spatial memory retrieval scores ($P < 0.05$) compared to the control group.
Upregulation of Hippocampal Antioxidant Enzymes: The activities of hippocampal SOD, GPx, and CAT enzymes in animals receiving RE (100 mg/kg) showed statistically significant increases compared to the normal control group ($P < 0.01$, $P < 0.01$, and $P < 0.05$, respectively). Additionally, GPx activity in the RE (50 mg/kg) group exhibited a significant increase relative to controls ($P < 0.05$).
Lipid Peroxidation & Histology: No statistically significant differences were observed among the experimental groups regarding hippocampal MDA levels.
Safety & Tolerability: The multi-week oral administration protocols were well-tolerated, maintaining high biological safety.
- Conclusions
Rosemary extract standardized to 40% carnosic acid improves spatial memory scores and enhances hippocampal antioxidant enzyme activities in middle-aged rats in a pronounced, dose-dependent manner, identifying the 100 mg/kg/day dosage as optimal for therapeutic efficacy. These empirical findings underscore standardized rosemary extract as a promising, dose-optimized botanical nutraceutical strategy for mitigating age-related cognitive decline and oxidative stress.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4431423/