Open AccessArticle
Evaluation of the Bitterness of Traditional Chinese Medicines using an E-Tongue Coupled with a Robust Partial Least Squares Regression Method
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Zhaozhou Lin 1,2,†, Qiao Zhang 2,†, Ruixin Liu 3,4,5,*, Xiaojie Gao 6, Lu Zhang 3,4,5, Bingya Kang 3,4,5, Junhan Shi 3,4,5, Zidan Wu 6,7, Xinjing Gui 6 and Xuelin Li 3
1
Institute of Clinical Pharmacy, Beijing Municipal Health Bureau, Beijing 100035, China
2
School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing 100102, China
3
Department of Pharmacy, The First Affiliated Hospital of Henan University of Traditional Chinese Medicine, Zhengzhou 450000, China
4
The Level Three Laboratory of Chinese Traditional Medical Preparation of State Administration of TCM, Zhengzhou 450000, China
5
Key Laboratory of Viral Diseases Prevention and Treatment of TCM of Henan Province, Zhengzhou 450000, China
6
School of pharmacy, Henan University of Traditional Chinese Medicine, Zhengzhou 450008, China
7
Department of Computer Science and Statistics, University of Rhode Island, Kingston, RI 02881, USA
†
These authors contributed equally to this work.
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Abstract
To accurately, safely, and efficiently evaluate the bitterness of Traditional Chinese Medicines (TCMs), a robust predictor was developed using robust partial least squares (RPLS) regression method based on data obtained from an electronic tongue (e-tongue) system. The data quality was verified by the
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To accurately, safely, and efficiently evaluate the bitterness of Traditional Chinese Medicines (TCMs), a robust predictor was developed using robust partial least squares (RPLS) regression method based on data obtained from an electronic tongue (e-tongue) system. The data quality was verified by the Grubb’s test. Moreover, potential outliers were detected based on both the standardized residual and score distance calculated for each sample. The performance of RPLS on the dataset before and after outlier detection was compared to other state-of-the-art methods including multivariate linear regression, least squares support vector machine, and the plain partial least squares regression. Both R
2 and root-mean-squares error (RMSE) of cross-validation (CV) were recorded for each model. With four latent variables, a robust RMSECV value of 0.3916 with bitterness values ranging from 0.63 to 4.78 were obtained for the RPLS model that was constructed based on the dataset including outliers. Meanwhile, the RMSECV, which was calculated using the models constructed by other methods, was larger than that of the RPLS model. After six outliers were excluded, the performance of all benchmark methods markedly improved, but the difference between the RPLS model constructed before and after outlier exclusion was negligible. In conclusion, the bitterness of TCM decoctions can be accurately evaluated with the RPLS model constructed using e-tongue data.
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