In vitro biological activities of black pepper essential oil and its major components relevant to the prevention of Alzheimer’s disease

Abstract

Black pepper oil and its major components were investigated for the biological activities related to the prevention of AD. The inhibition of acetylcholinesterase (AChE) and ß-amyloid aggregation, anti-inflammatory and antioxidant activities were examined. GC-MS analysis of black pepper oil identified 33 constituents with d-3carene, limonene, (-)-ß-pinene, a-pinene and caryophyllene as the main components. The AChE inhibitory activity by microplate assay revealed that black pepper oil exhibited potent AChE inhibition with an IC50 value of 5.97 µg/ml. Among the compounds tested, d-3-carene exhibited AChE inhibitory activity with an IC50 value of 20.50 µg/ml. ß-Amyloid aggregation inhibitory activity was determined by a thioflavin T assay. Black pepper oil exhibited a weak inhibitory activity with 33.17 ± 6.67% inhibition at 100 µg/ml, while limonene possessed stronger inhibitory activity with an IC50 value of 3.77 µg/ml. Anti-inflammatory activity was determined by a COX-2 activity assay in THP-1 cells. The oil and caryophyllene showed strong COX-2 inhibition. The weak antioxidant activity of black pepper oil and its major components was observed in TLC/DPPH, microplate assays and ESR analysis. These findings suggest that black pepper oil may be beneficial in lowering the risk of Alzheimer’s disease via AChE inhibition and anti-inflammatory activity via COX-2 inhibition.