An Integrated LC-ESI-MSn and High Resolution LC-ESI-QTOF Approach for the Identification of Phloroglucinols from Nepalese Hypericum japonicum

Abstract

Phloroglucinols are characteristic constituents of Hypericumjaponicum that are claimed to exert several bioactivities, such as anti-inflammatory, anti-depressant and anti-viral ones. Phloroglucinols are unstable compounds and their synthesis is challenging; thus, isolation from natural sources is still one of the main strategies for obtaining these constituents in purified form. Assessing the presence of phloroglucinols in plant materials can be of interest for compound isolation, and LC-MS approaches afford sensitivity and specificity in this regard. In this work, we combined data from quadrupole-time of flight (QTOF) and ion trap (IT) mass spectrometers in order to assess the presence of the phloroglucinols characteristic of H. japonicum and to elucidate their MS fragmentation pathways. The identified compounds present similar structures bearing the 1,3,5-trihydroxybenzene core with different substitutions, which, in constituents at higher MW, is linked to 3′,3′-dimethyl-6′-oxo-phlorisobutyrophenone by a methylene bridge. Differences in MS2 spectra of the considered phloroglucinols are useful for compound identification and differentiation, and to perform dereplication studies. Overall, the proposed approach could be useful for the analysis of phloroglucinols in H. japonicum and other plant species.

HPLC-based cytotoxicity profiling and LC-ESIQTOF-MS/MS analysis of Helichrysum leucocephalum

“…Scheme 2 , Figs. 11 A and 11B show the plausible fragmentation pattern for 11 based on previous similar studies reporting the fragmentation pathways of phloroglucinol derivatives [ [24] , [25] , [26] ]. Therefore, compound 11 was identified tentatively as helispiroketal C [ 11 ].…”

“…Data from tandem mass spectrometry (MS n ) showed that ion 293 breaks into ion 153, 141, and 125 ( Scheme 1 ). According to literature survey [ [24] , [25] , [26] ], this fragmentation pattern can be attributed to a homopyrone derivative namely helipyrone C ( Fig. 10 A & B).…”

“…Thus, according to the MS and MS/MS data and similarity search with our in-house library, compound 15 and 16 were tentatively identified as geranylated homologues of helispiroketal C ( Table 4 , Fig. 12 , and Scheme 3 ) [ [24] , [25] , [26] ].

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“…Therefore, compounds 13 and 17 were also plausibly identified as geranylated α,β-spiroketal phloroglucinols. A proposed fragmentation pattern is illustrated in Scheme 3 for these derivatives [ [24] , [25] , [26] ].…”

Dereplication of natural cytotoxic products from Helichrysum oligocephalum using ultra‐performance liquid chromatography–quadrupole time of flight‐mass spectrometry

“…In addition, the observed ion at m/z 154 might be due to the presence of the pyrone moiety. A plausible fragmentation pattern is outlined in Figure 6 [35]. Therefore, this compound was tentatively annotated as arenol which was first isolated and identified from the plant Helichrysum arenarium in 1971 [36].…”