Correlation between macroscopic characteristics and tissue-specific chemical profiling of the root of Salvia miltiorrhiza

Abstract Background Macroscopic identification has been widely used as a convenient method for herbal authentication and quality assessment. However, sensory evaluation heavily relied on personal experience and lacked enough evidence-based validations. Purpose We aim to reveal the correlation between macroscopic characteristics and tissue-specific chemical composition of the root of Salvia miltiorrhiza (SMR), and then develop a rapid method for quality assessment. Methods Thirty-two batches of SMR were collected and evaluated. The outer-surface color and diameter as the representative tissue features of SMR were selected as the macroscopic indexes. SMR were then divided into three parts along transverse section as outer bark, middle part and central part, to explore the spatial distribution of chemicals. Outer-surface color information was converted into RGB values, while the diameter data were expressed by mean distance, respectively. Thirteen major components including eight salvianolic acids and five tanshinones in each part were determined by liquid chromatography tandem mass spectrometry. Finally, several mathematical models were established and optimized to evaluate the correlation between outer-surface color, size and chemical distribution. Result All five tanshinones mainly distributed in the outer bark while salvianolic acids were averagely existed among three parts. Correlational studies revealed that the surface color depth was significantly and positively correlated with tanshinone contents in the outer bark, while the size showed poor correlation in any chemicals. A color-oriented model was thus developed for the prediction of tanshinone contents in SMR, and a 9 × 9 standard color chart was created for easily use. Conclusion This study contributes an alternative method for macroscopic features-based quality evaluation of herbs, and also complements some scientific data for traditional knowledge.