Phytochemical profiling and chemical marker compounds identification in Helichrysum caespititium: A chemometrics and 2D gas chromatography time of flight mass spectrometry (GCxGC-TOF-MS) perspective

Introduction: Helichrysum caespititium is a medicinal plant indigenous to South Africa. Hitherto, only 2 compounds- caespititin and 2-methyl-4-[2’,4’,6’-trihydroxy-3’-(2-methylpropanoyl)-phenyl] but-2-enyl acetate have been reported from this species. Phytochemical profiling of the plant and identification of chemical markers are limited. Objectives: Determining phytochemical profile of H. caespititium and identifying the major marker compounds in its extracts. Methods: A two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF-MS) was used to analyze H. caespititium extracts (acetone, methanol, and dichloromethane). The marker compounds from the generated phytochemical fingerprints were identified using Column plots and chemometrics orthogonal partial least squares discriminant analysis (OPLS-DA). Polar acetone, methanol, and non-polar dichloromethane extracts were analyzed separately. Results and Discussions: A total of 135 (12 from acetone, 13 from methanol, and 110 from dichloromethane extracts) compounds were identified in H. caespititium. An OPLSDA score plot with R² = 0.81 grouped the polar compounds into 2 clusters as phenolic and non-phenolic compounds, while a contribution plot from the score plot then nominated benzene[(methoxymethoxy)]methyl, 4-methyl-2,4-bis(p-hydroxyphenyl)penet-1-ene, isoeugenol, and 3 4-dihydroxymandelic acid as marker compounds in the polar extracts. In a second plot with R² = 0.67, the corresponding contribution plot accentuated 2-methyl-5-(fur-3-yl) pent-3-en-2-ol, 3,5-dimethyl-4-heptanone, 1,2-benzenedicarboxylic acid, dihexyl-1-(4methylphenyl)-5(2-dimethyl aminothenyl)-1H-tetrazole, and 3,5-dimethyl-4-heptanone as the marker compounds in the dichloromethane extract. Conclusion: This study recommends the use of the marker compounds as quality standard of raw materials and commercial products containing extracts or other forms of the South African H. caespititium.