ABSTRACT
The paper-based analytical device (PAD) was applied in this study to analyze the antioxidant activity of Danhong injection and its intermediates. First polycaprolactone was printed on the surface of a filter paper with a 3D printing device. The modified filter paper was then prepared using polycaprolactone and solid paraffin as the modifiers. The PAD was prepared after adding DPPH ethanol solution to the modified filter paper. Ascorbic acid solutions with different concentrations were used as the positive drug on PAD. After the occurrence of color reactions, the PAD was dried, and the data of color were collected by a cell phone. The color component G and grayscale were selected as the potential indices for measurement according to the values of determination coefficients, detection limits, and effective number of digits. Qualitative and quantitative analysis of Danhong injection and the concentrate of aqueous extract were realized with the PAD. Because no significant differences were observed between the results obtained using the two potential indices, the average values of these two were used for analysis, and the antioxidant activity of Danhong injection and the concentrate of aqueous extract was equivalent to ascorbic acid solutions of 3.7, 46 g·L⁻¹, respectively. The PAD method presented in this work can be a simple method to determine biological activities of Chinese medicines and their intermediates.