Favorable effects of dill tablets and Ocimum basilicum L. extract on learning, memory, and hippocampal fatty acid composition in hypercholesterolemic rats

Hypercholesterolemia is correlated with brain amyloid-β (Aβ) deposition and impaired cognitive functions and contributes to Alzheimer’s disease. Effects of cholesterol-lowering dill tablets and aqueous extract of Ocimum basilicum L. (basil) on learning and memory and hippocampus fatty acid composition were examined.  mRNA levels of the genes involved in cholesterol homeostasis were also determined in high-cholesterol diet (HCD) fed rats.   Forty male Wistar rats were allocated to 4 groups: rats fed chow diet (C); rats fed high-cholesterol (2%) diet (HCD); rats treated with HCD+300 mg/kg dill tablets (HCD+Dill); and finally, rats fed HCD and treated with 400 mg/kg basil aqueous extract (HCD+basil).  Treatment was carried out for 16 weeks.  Hippocampus Aβ(1-42) level was determined. Spatial and passive avoidance tests were used to examine cognitive functions.  Hippocampal FA composition was assessed by gas chromatography. Basil aqueous extract was analyzed by GC-double mass spectroscopy (GC-MS/MS) and expression of LXR-α, LXR-β, and ABCA1 genes was assessed by qRT-PCR.   Dill tablets and basil extract remarkably ameliorated serum cholesterol (p <0.001), retarded hippocampal accumulation of Aβ, and attenuated HCD-induced memory impairment.  Hippocampus FA composition did not change but serum cholesterol was found positively correlated with hippocampus Aβ(1-42) (p <0.001), total n 6 PUFA (P=0.013), and Aβ(1-42) showed correlation with the ratio of n6 to n3 PUFA.  At least 70 components were identified in basil aqueous extract.   Dill tablets and aqueous extract of basil attenuated the hypercholesterolemia-induced memory impairment by lowering serum cholesterol and hippocampus amyloid deposits, and probably beneficial in AD adjuvant therapy.