[Grading criteria for Gentianae Macrophyllae Radix pieces based on theory of quality evaluation through morphological identification].

The traditional quality evaluation of Gentianae Macrophyllae Radix(GMR) considers long, large and yellowish-white roots are better, yet the scientific connotation of these appearance characteristics remains to be elucidated, with systematic research on the grading criteria of GMR pieces still lacking. According to the theory of quality evaluation through morphological identification, this study investigated the correlation between appearance characteristics and intrinsic components through quantitative measurements, foreign matter detection, and determination of extract yield and total content of gentiopicroside and loganic acid(GL). With relative quality constant(RQC) as an indicator, correlation analysis, orthogonal partial least squares-discriminant analysis(OPLS-DA), and regression analysis were employed to explore the correlations between appearance characteristics and component content, and thus the quality grading criteria for GMR pieces were established. The results showed that when 60% of maximum RQC was set as the grading threshold, premium-grade pieces showed RQC≥12.46, while commercial-grade pieces showed RQC<12.46. The GL content showed significantly positive correlations with piece diameter, mass, and brightness(L~*) but a significantly negative correlation with foreign matter content. Diameter, foreign matter content, and GL content were the key indicators for grading. Critical classification indicators of premium-grade pieces were determined as diameter≥1.4 cm, foreign matter≤0.4%, and GL content≥6.4%. This study confirms that key appearance characteristics(diameter and color) and related foreign matter can serve as quality evaluation parameters, scientifically interprets the traditional criterion of long, large, and yellowish-white roots being better, and lays a theoretical foundation for establishing objective and scientific appearance characteristic standards of GMR pieces.