The discovery of new active compounds of natural products tends to be increasingly more challenging due to chemical complexity and unpredictable matrices. Forskolin is an active natural labdane-type diterpenoid ingredient widely used worldwide for the treatment of glaucoma, heart failure, hypertension, diabetes, and asthma, and is expected to be a promising anticancer, anti-inflammation, and anti-HIV agent. In recent years, demand for forskolin in the medicine market has increased dramatically. However, natural forskolin originates exclusively from traditional Indian herb medicine Coleus forskohlii (Willd.) Briq. In a previous study, we isolated a series of diterpenoids including an 8,13-epoxy-14ene labdane carbon skeleton from Blumea aromatica DC. In order to identify alternative plant resources, a novel and effective strategy was proposed for the screening of potential forskolin-type diterpenoids (FSKD) compounds obtained from B. aromatica, using the mass defect filtering (MDF) strategy via ultra-high-performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) approach. Within a narrow, well-defined mass defect range, the strategy developed could significantly improve the detection efficiency of selected FSKD compounds by filtering out certain major or moderate interference compounds. Additionally, the MS/MS cleavage behavior and the characteristic diagnostic ions of the FSKD compounds were proposed to be used in aiding structural identification of the filtration compounds. As a result, a total of 38 FSKD of B. aromatica were filtered out and tentatively identified. To the best of our knowledge, it was the first time that these forskolin-type diterpenoids were identified in B. aromatica, which significantly expands our understanding of the chemical constituents of Blumea species, and allows B. aromatica to be used as a potential alternative plant resource that contains these forskolin-type active compounds. The strategy proposed was proven efficient and reliable for the discovery of novel compounds of herbal extracts.
Keywords: Blumea aromatica DC; UHPLC-QTOF-MS/MS; diterpenoids; foskolin; mass defect filter.