Abstract
The root of Prismatomeris connata has been used in China for centuries as the medicinal herb “Huang Gen” (HG), but its phytochemicals or active ingredients are not well understood. In this study, we performed chemical analysis of the ethyl acetate fraction of a HG ethanol extract. We thus isolated seven new tetrahydroanthraquinones, prisconnatanones C–I (compounds 1–7) from the root of P. connata and identified their structures using spectroscopic analyses. Their absolute configurations were established by both modified Mosher’s and Mo2OAc4 methods, and ORD techniques. Their cytotoxicity was tested in a panel of human lung tumor cells (H1229, HTB179, A549 and H520 cell lines). Prisconnatanone I (7) showed the highest activity, with an IC50 value ranging from 2.7 µM to 3.9 µM in the suppression of tumor cell growth, and the others with chelated phenolic hydroxyls exhibited relatively lower activity (IC50: 8–20 µM). In conclusion, these data suggest that some of the natural tetrahydroanthraquinones in HG are bioactive, and hydroxylation at C-1 significantly increases the cytotoxicity of these compounds against lung tumor cell growth.
Highlights
The root of Prismatomeris connate, termed “Huang Gen” (HG) in Chinese herbal medicine, has been used in traditional medicine in China for the treatment of hepatitis, anaemia, leucocythemia, and pneumoconiosis [1,2,3]
Many secondary metabolites, including anthraquinones, anthraquinone glycosides, and iridoids have been identified in HG extracts in earlier studies [4,5,6,7,8,9,10], and in our previous study, two tetrahydroanthraquinones have been successfully isolated, and prisconnatanone A showed a significant cytotoxicity against the A549 lung tumor cell line [9]
The 95% EtOH HG extract was successfully fractionated with petroleum ether (PE), ethyl acetate (EtOAc), and n-butanol (BuOH)
Summary
The root of Prismatomeris connate, termed “Huang Gen” (HG) in Chinese herbal medicine, has been used in traditional medicine in China for the treatment of hepatitis, anaemia, leucocythemia, and pneumoconiosis [1,2,3]. Many secondary metabolites, including anthraquinones, anthraquinone glycosides, and iridoids have been identified in HG extracts in earlier studies [4,5,6,7,8,9,10], and in our previous study, two tetrahydroanthraquinones (prisconnatanones A and B) have been successfully isolated, and prisconnatanone A showed a significant cytotoxicity against the A549 lung tumor cell line [9]. This study aimed at further chemical analyses of the phytocomponents in the ethyl acetate (EtOAc) fraction of a HG ethanol extract. In addition to the two known tetrahydroanthraquinone compounds, we identified seven new tetrahydroanthraquinones, prisconnatanones C–I We report the isolation, structure identification, and biological activities of these new natural compounds
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