Qualitatively and quantitatively comparing secondary metabolites in three medicinal parts derived from Poria cocos (Schw.) Wolf using UHPLC-QTOF-MS/MS-based chemical profiling

Poria cocos (Schw.) Wolf, is a fungus that grows on dead pine roots, producing a solid white sclerotium (fruiting body). Three parts of the sclerotium are commonly used in traditional Chinese medicine, namely, the epidermis, known as Poria Cutis or fulingpi in Chinese; the middle part, known as Poria or baifuling; and the sclerotium with some host attached, known as fushen. For fushen, the hostwood is the inner part, known as fushenmu. The epidermis, middle part and middle-plus-inner parts have long been used for different syndromes or diseases, but the differences in their chemistry have not been established. In this study, ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UHPLC-QTOF-MS/MS) was used to explore the differences of secondary metabolites in these three botanical parts of Poria cocos. In 13 batches of samples, a total of 147 chromatographic peaks were unequivocally or tentatively identified. Of these, 15 peaks were common to all three parts (the epidermis, middle, and inner part), while the rest were found in only one or two of the parts. Meanwhile, dissimilarities among the chemical compositions of three botanical parts were further investigated by principal component analysis (PCA), and supervised orthogonal partial least squares-discriminate analysis (OPLS-DA). Eight major bioactive triterpene acids that played important roles in differentiating the epidermis, middle and inner part were simultaneously quantified using the extracting ion mode of UHPLC-QTOF-MS/MS. The quantitative results showed that the analytes accumulated mostly in the epidermis and inner part, with the least accumulation in the middle part. This systematic information on the differences in secondary metabolites in the three botanical regions of Poria cocos provides a factual chemical basis not only for discrimination in therapeutic practice but also for quality evaluation of Poria cocos.