Hypericum hirsutum L. (Hypericaceae) is a perennial herb with hirsute green parts that is native to Northern Africa, Europe and temperate Asia [1]. The chemical composition of the plant, especially the prenylated acylphloroglucinols which are very popular secondary metabolites in many species of the genus Hypericum (Hypericaceae), is so far mostly unknown. Chemical investigations of the petroleum ether raw extract of aerial parts of Hypericum hirsutum L. yielded four new polycyclic polyprenylated acylphloroglucinols with a rare tricyclo[4.3.1.1]undecane skeleton. Such complex caged benzophenone derivatives are hitherto unknown for the whole section 18 Taeniocarpium. Similar substances were already isolated from Hypericum sampsonii Hance (Hypericaceae, Sect. 9 Sampsonia) [2, 3] and Clusia obdeltifolia (Clusiaceae) [4]. The acylphloroglucinols were isolated by using Diaion® HP-20 column chromatography, silica gel flash chromatography, centrifugal partition chromatography, as well as semi-preparative RP-18 HPLC techniques. On basis of 1D and 2D NMR data the structures could be elucidated and with MS experiments they were confirmed.
References
[1] Robsen N. K. B. (2010): Studies in the genus Hypericum L (Hypericaceae) 5(2). Sections 17. Hirtella to 19. Coridium. In: Phytotaxa 4 (1), p. 203–207
[2] Hu, L.-H.; Sim, K.-Y. (1998): Complex Caged Polyisoprenylated Benzophenone Derivatives, Sampsoniones A and B, from Hypericum sampsonii. In: Tetrahedron Letters 39, p. 7999–8002
[3] Tian, W.-J.; Qiu, Y.-Q.; Jin, X.-J. (2014): Novel polycyclic polyprenylated acylphloroglucinols from Hypericum sampsonii. In: Tetrahedron 70, p. 7912–1916
[4] Cruz, F.; Teixeira, J. (2004): Polyprenylated Benzophenones with a Tricyclo [4.3.1.13,8]Undecane Skeleton from Clusia obdeltifolia. In: Journal of the Brazilian Chemical Society, Vol. 15, No. 4, p. 504–508