Homoadamantane and Adamantane Acylphloroglucinols from Hypericum hirsutum

Abstract

1H NMR-guided fractionation of the petroleum ether extract of the aerial parts from Hypericum hirsutum yielded to the isolation of 19 polyprenylated polycyclic acylphloroglucinols. Structure elucidation based on 1D and 2D NMR spectroscopy together with high-resolution electrospray ionization mass spectroscopy revealed 14 acylphloroglucinols with a homoadamantane scaffold (1–14), while 5 further compounds showed an adamantane skeleton (15–19). Except for hookerione C (15), all isolated metabolites are hitherto unknown. While structurally-related metabolites have been isolated from other Hypericum species, it is the first report of admantan and homoadamantan type acylphloroglucinols in section Taeniocarpium Jaub. & Spach (Hypericaceae). The isolated compounds have been tested in a crystal violet-based in vitro assay on their properties to reduce the proliferation of human microvascular endothelial cells compared to hyperforin as the positive control. They showed a moderate reduction of proliferation with IC50 values in the range ~ 3 – 22 µM, with the homoadamantane-based compounds 2 and 4 being the most active. In addition, inhibition of the TNF-α-induced ICAM-1 expression was determined for 1 – 5, 7, and 10 – 12. Substances 3 and 12 reduced the ICAM-1 expression significantly (to 46.7% of control for 3, 62.3% for 12, at 50 µM).

Outstanding Antibacterial Activity of Hypericum rochelii—Comparison of the Antimicrobial Effects of Extracts and Fractions from Four Hypericum Species Growing in Bulgaria with a Focus on Prenylated Phloroglucinols

“…Its hypericin [ 77 ] and hyperforin [ 78 ] contents are lower than in H. perforatum [ 72 , 79 ]. The plant also contains many PPAPs with homoadamantane and adamantane skeletons [ 80 ], phenolic acids [ 81 ] and other phenolic compounds [ 82 ], such as avicularin [ 78 ], amentoflavone [ 83 ], etc.…”