Evaluation of Medicinal Quality of Garlic Based on Principal Component Analysis

To compare and analyze the medicinal quality of garlic, a garlic medicinal quality evaluation system was established. Moisture, ash, water-soluble extract, diallyl trisulfide content, alliin content, allicin content and alliinase activity were screened out as indicators to analyze the medicinal quality of garlic from 11 regions, including Minle, Pizhou, Jinxiang, Zhengzhou, Wuxi, Qiemo, Baicheng, Zhongmachang, Hutou, Dayou and Xindi. The correlation analysis, principal component analysis and cluster analysis were performed to determine the quality of garlic in different regions. The results showed that all the above-mentioned indicators of garlic from different regions had significant differences. The correlation analysis showed that alliinase activity had an extremely significant and positive correlation with moisture (P<0.01), and alliin content showed a significant positive correlation with ash and alliin content (P<0.05). Three principal components with a cumulative contribution of 81.134% could be selected using the principal component analysis. Among the first principal component with the largest contribution, alliin had the greatest influence on the medicinal quality of garlic, followed by allicin and alliinase activity. In the comprehensive evaluation of garlic from 11 regions, the highest score of 1.44 was obtained from Minle, and the remaining four scores greater than zero were all from Xinjiang. The systematic clustering analysis revealed that the garlic from 11 regions could be clustered into four categories. Among them, Zhengzhou garlic was a separate category. Jinxiang, Wuxi and Zhongmachang garlic were clustered into one category. Xindi, Dayou and Minle garlic were clustered into one category, and the remaining three regions were clustered into one category. Alliin, allicin and alliinase activity could be used to reflect the disparity between the medicinal quality of garlic from different regions. The garlic with the highest overall score could be screened using the integrated score, which would provide ideas for the research of germplasm resources of high-quality garlic and the large-scale cultivation of medicinal garlic.