Fig. 5: Rapid identification of salvianolic acids in natural herbs.

a A workflow of nanopore identification of salvianolic acids directly from natural herbs. The gray timeline stands for the time of the whole procedure and red bars represent the time of human operation. Phase I: Sample pretreatment. Natural herbs were crushed and soaked in Milli-Q water for 12 h at 4 °C. Human operations: herb crushing and soaking (5 min). Phase II: Liquid collection. The soaking liquid was centrifuged at 4 °C and 1500 g for 10 min and the supernatant was collected. Human operations: centrifugation preparation (1 min) and supernatant collection (1 min). Phase III: Ultrafiltration. The collected supernatant was treated with a 3 kDa ultrafiltration tube at 4 °C and 1900 g for 30 min and the filtrate was collected. Human operations: ultrafiltration preparation (1 min) and filtrate collection (1 min). Phase IV: Nanopore sensing. 20 μL filtrate was added to the cis chamber of a nanopore device. Human operations: sample addition (10 s). Phase V: Data analysis. Human operations: automatic data analysis by machine learning (2 min). A more detailed workflow was also described in Methods and Supplementary Fig. 23. b, e, h Three types of commercially available natural herbs including (b) Salvia miltiorrhiza, (e) Rosemary and (h) P. vulgaris and their corresponding soaking liquids. c, f, i Representative nanopore traces acquired with different herb samples. All events were identified by the trained KNN model and correspondingly labeled as RA (blue), LSA (wine-red), SalB (orange), PA (red), SalA (lavender) and others (black). The ‘other’ events represent events that don’t belong to any previously trained salvianolic acid model compounds, based on results of outlier analysis (Supplementary Figs. 24, 26, 27). d, g, j The proportion of salvianolic acid events from results acquired with (d) Salvia miltiorrhiza, (g) Rosemary and (j) P. vulgaris (Supplementary Figs. 25, 28, 29). Data were presented as mean ± standard deviation values derived from results of three independent measurements (N = 3). The error bars represent standard deviation values. All above described results were acquired by nanopore measurement using MspA-90PBA in a buffer of 1.5 M KCl, 100 mM MOPS, pH 7.0 and a + 100 mV bias, which was continually applied. Source data are provided as a Source Data file.