HPLC/UHPLC analysis

Liquid chromatography (LC), including HPLC and UHPLC, is frequently and consistently utilized as an effective and excellent means for the identification and quantitative determination of compounds due to its accessibility, ease of operation, high sensitivity and reproducibility, good resolution and linearity, and the ability to analyze a diverse range of components. It is one of the common techniques used for the quality assessment of C. rotundus. In practical terms, certain conditions of analysis, consisting of analytes type, mobile phase, mobile phase flow rate, column temperature, column type, eluent program and detector, are critical factors affecting HPLC analysis. Supplementary Table S18 reveals the detailed conditions for the HPLC approach with regard to the analyses of C. rotundus.

It could be found that most of the analytes subjected to LC analysis of C. rotundus are the major sesquiterpenoid components, as well as the phenolic components. The mobile phases are commonly methanol–water or acetonitrile–water, with the addition of 0.1–0.5% formic acid, acetic acid, or trifluoroacetic acid to the aqueous phase. Varied columns and different detectors (such as PDA, DAD and MS) are now frequently equipped for the qualitive or quantitative analyses.

As is reported, the contents of mesocyperusphenol A (499), scirpusins A (494) and β-sitosterol (422) were evaluated in C. rotundus from different regions in China by UPLC and HPLC. The results indicated that the content of active ingredients in C. rotundus from Shandong, was relatively higher than those of other regions, revealing the necessity of selecting authentic and genuine herbs (Cao and Ou 2015; Deng et al. 2016). Zhao et al. established an HPLC method for fingerprinting the chemical components in the methanolic extracts of eight batches of C. rotundus from different regions, as well as similarity evaluation and clustering analysis (Zhao et al. 2008). Deng et al. have developed an approach for effective and rapid affinity-based screening of natural α-glucosidase inhibitors directly from C. rotundus extracts by utilizing an immobilized enzyme technique integrated with UHPLC-QTOF-MS analysis (Deng et al. 2019). Also, tissue-specific metabolite analyses of C. rotundus from India and China by laser microdissection, UHPLC-QTOF-MS/MS and additional GC–MS have been conducted and the outcomes demonstrated that the content of ( +)-nootkatone (235) in C. rotundus of India (30.47 μg/10 g), was higher than that of China (21.72 μg/10 g) (Jaiswal et al. 2014). Furthermore, LC–ESI–MS/MS was employed to characterize the phytochemical composition of the total oligomeric flavonoid (TOF) of C. rotundus and simultaneously to determine its total flavonoid and total phenolic (TPC) content (Kandikattu et al. 2015).