Screening of angiotensin converting enzyme inhibitors from natural products via origami microfluidic paper-based...

We report the screening of angiotensin converting enzyme (ACE) inhibitors on an origami microfluidic paper-based analytical device (μPAD) using colorimetric detection. The hydrolysis product reacts with ninhydrin, resulting in a purple color at the detection zones. Images of the μPADs are captured using a common cell phone and analyzed with Photoshop software. This platform allows six independent colorimetric reactions to take place simultaneously, and the IC₅₀ values can be obtained in a single run within 22 min. The relative standard deviations of inhibition efficiencies are generally lower than 4.0 % (n = 5). The IC₅₀ values of captopril and five products from natural plants were obtained and corresponded well with UV methods. The relative deviations between the two methods are within the range of -5 % to +5 %. This work is a proof-of-concept successfully demonstrating the use of μPADs technology to screen enzyme inhibitors from natural products.