Prenylated acylphloroglucinols from Hypericum annulatum

The genus Hypericum L. (Hypericaceae) includes more than 480 species that are found in every continent of the world, except Antarctica [1]. Hypericum annulatum Moris is a perennial herb distributed in Sardinia, Balkans, East Africa and Saudi Arabia [2]. A phytochemical investigation of the hexane extract of the aerial parts of the titled species led to the isolation of three new (1 – 3) and a known (4) prenylated acylphloroglucinol derivatives (Fig. 1). The new compounds were identified as 1-{3-[(3E)-3,7-dimethyl-2-(3-methylbut-2-en-1-yl)octa-3,6-dien-1-yl]-2,4,6-trihydroxyphenyl}-2-methylpropan-1-one (1), 1-{3-[(3E)-3,7-dimethyl-2-(3-methylbut-2-en-1-yl)octa-3,6-dien-1-yl]-2,4,6-trihydroxyphenyl}-2-methylbutan-1-one (2) and 1-((4aS,9aR)-6,8-dihydroxy-3,3-dimethyl-4a-(4-methylpent-3-en-1-yl)-2,3,4,4a,9,9a-hexahydro-1 H-xanthen-5-yl)-2-methylpropan-1-one (3) by means of spectral methods (MS, NMR, IR, UV). The known compound has been identified as hypercalyxone A (4) by comparing its spectral data with that reported in the literature [3]. The cytotoxicity of isolated compounds were established on a panel of tumor cell lines (EJ, HL-60, HL-60/DOX, MDA-MB, SKW-3, BV-173 and K-562) was determined using MTT based assays. Copounds 1 and 2 were the most cytotoxic with IC₅₀ values ranging from 0.61 to 4.63 µg/mL.

References:

[1] Crockett SL, Robson NK. Med Aromat Plant Sci Biotechnol. 2011; 5: 1 – 13.

[2] Robson NKB. Bull Nat Hist Mus (London), Bot. 1996; 26: 75 – 271.

[3] Winkelmann K, San M, Kypriotakis Z, Skaltsa H, Bosilij B, Heilmann J. Z Naturforsch. 2003; 58c: 527 – 532.