Similarities and differences between Ziqin and Kuqin in anti-inflammatory, analgesic, and antioxidant activities and their core chemical composition based on the zebrafish model and spectrum-effect relationship

Ethnopharmacological relevance: Scutellaria baicalensis (SB) is a traditional Chinese medicine (TCM). In the clinical application of TCM, SB has been divided into two specifications (Ziqin and Kuqin) for a long time. At present, the Chinese Pharmacopoeia Commission no longer distinguishes between the two. However, the two specifications of medicinal materials and pieces are still in circulation in the market. Aim of the study: This work aimed at investigating the similarities and differences between Ziqin and Kuqin in anti-inflammatory, analgesic, and antioxidant activities and their material basis. It will provide a new angle for relevant regulations to formulate the specifications and standards of SB. Materials and methods: Here we investigated the similarities and differences between Ziqin and Kuqin in anti-inflammatory, analgesic, and antioxidant activities related to four zebrafish models and three chemical tests. The chemical fingerprints of SB (Ziqin and Kuqin) were profiled by HPLC. Meanwhile, UHPLC-Q-TOF/MS was used to identify the chemical constituents of Ziqin and Kuqin. The main effect-related compounds of SB, Ziqin, and Kuqin were screened out by spectrum-effect relationship. Finally, six monomeric compounds were validated experimentally using the zebrafish inflammation model induced by CuSO₄. Results: Both Ziqin and Kuqin had significant anti-inflammatory, analgesic, and antioxidant activities. Kuqin had better anti-inflammatory and analgesic activities, while Ziqin had better antioxidant activity. HPLC fingerprint and UHPLC-Q-TOF/MS evaluation showed that the chemical composition types and main components of Ziqin and Kuqin were basically the same, while the contents and proportions of chemical components in Ziqin and Kuqin were different. By spectrum-effect relationship, compounds X1, X2 (luteoloside), X3, X4 (baicalin), X6 (wogonoside), X7 (baicalein), X8 (wogonin), and X9 (oroxylin A) were the same active chemical constituents of Ziqin and Kuqin. The core components of anti-inflammatory and analgesia activities in Kuqin were compounds X1, X2, X3, X5, X6, X7, X8, and X9. The antioxidant core active components of Ziqin were compounds X2, X3, X4, X6, X7, and X9. Among them, luteoloside, baicalin, wogonoside, baicalein, wogonin, and oroxylin A were validated successfully with good anti-inflammatory effects. Conclusions: This study revealed that Ziqin and kuqin have high similarity in chemical composition, but their proportions and active core components are different. This may be one of the main reasons why they have the same activity but different activity trends. These findings will help to improve the understanding of the different clinical applications of Ziqin and Kuqin, and provide a reference for the formulation of quality standards and their further research.