Alzheimer's disease (AD) is a progressive neurodegenerative disorder of insidious onset that causes gradual loss of memory and cognitive function, and it is the most common form of dementia in the elderly. AD is characterized by neuritic plaques and neurofibrillary tangles in the brain, together with loss of neuronal cells. The major neuropathological hallmark of AD is the accumulation of extracellular neurotoxic β-amyloid (Aβ) peptides, such as Aβ1-42, in the brain. In the present study, we investigated the effect of sargachromenol (SCM), sargaquinoic acid (SQA) and sargahydroquinoic acid (SHQA) isolated from Sargassum serratifoilum ethanol extract (SSE) on Aβ production in vitro using APP751-transfected Chinese hamster ovary cells (CHO-751). CHO-751 cells were treated with various concentrations of SSE, SCM, SQA and SHQA, and the level of extracellular Aβ1-42 was evaluated by enzyme-linked immunosorbent assay. SSE and SHQA reduced the production of Aβ1-42 in CHO-751 cells. Therefore, SHQA isolated from S. serratifolium has potential as an inhibitor of neurotoxic Aβ peptide production.