Summary: | The aggregation and accumulation of amyloid β (Aβ) in the brain is a trigger of pathogenesis for Alzheimer’s disease. Previously, we developed a microliter-scale high-throughput screening (MSHTS) system for Aβ<sub>42</sub> aggregation inhibitors using quantum-dot nanoprobes. The MSHTS system is seldom influenced by contaminants in samples and is able to directly evaluate Aβ<sub>42</sub> aggregation inhibitory activity of samples containing various compounds. In this study, to elucidate whether the MSHTS system could be applied to the evaluation of processed foods, we examined Aβ<sub>42</sub> aggregation inhibitory activity of salad dressings, including soy sauces. We estimated the 50% effective concentration (EC<sub>50</sub>) from serial diluted dressings. Interestingly, all 19 commercial dressings tested showed Aβ<sub>42</sub> aggregation inhibitory activity. It was suggested that EC<sub>50</sub> differed by as much as 100 times between the dressings with the most (0.065 ± 0.020 <i>v</i>/<i>v</i>%) and least (6.737 ± 5.054 <i>v</i>/<i>v</i>%) inhibitory activity. The highest activity sample is traditional Japanese dressing, soy sauce. It is known that soy sauce is roughly classified into a heat-treated variety and a non-heat-treated variety. We demonstrated that non-heat-treated raw soy sauce exhibited higher Aβ<sub>42</sub> aggregation inhibitory activity than heat-treated soy sauce. Herein, we propose that MSHTS system can be applied to processed foods.
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