Planta Med 2009; 75 - PE7
DOI: 10.1055/s-0029-1234568

Absolute structures of Salvileucalin A and B from Salvia leucantha Cav.

K Takeya 1, Y Aoyagi 1, A Yamazaki 1, C Nakatsugawa 1, H Fukaya 1, S Kawauchi 2, H Izumi 3
  • 1Tokyo University of Pharmacy & Life Sciences, 1432–1 Horinouchi, Hachioji, 192–0392 Tokyo, Japan
  • 2Tokyo Institute of Technology, Ookayama, Meguro-ku, 152–8552 Tokyo, Japan
  • 3National Institute of Advanced Industrial Science and Technology, 16–1 Onogawa, Tsukuba, 305–8569 Ibaraki, Japan

From the aerial parts of Salvia leucantha of the subgenus Calosphace (Labiatae), an evergreen herbaceous perennial in the frost-free climate area, some rearranged neoclerodane diterpenes were isolated by Esquivel et al. [1], and another highly rearranged diterpene, spiroleucantholide (3), having a spiro skeleton in the molecule, by Takeda et al. [2]. In our study, salvileucalin B (2), having an unprecedented rearranged neoclerodane skeleton, was isolated from the aerial parts of this plant along with salvinoleucalin A (1) [3]. The absolute structures were elucidated by spectroscopic analysis, X-ray crystallographic analysis and vibrational circular dichroism (VCD). Compound 2 represents a novel clerodane diterpene, characterized by a tricycle[3.2.1.02,7]octane substructure incorporating the exocyclic C-20 methylene of 1. Salvileucalin B (2) exhibited cytotoxicity against A549 and HT-29 cells with IC50 values of 5.23 and 1.88 µg/mL, respectively.

References: [1] Esquivel, B. et al. (1994) Tetrahedron 50:11593–11600.

[2] Narukawa, Y. et al. (2006)J. Nat. Med. 60:206–209.

[3] Aoyagi, Y. et al. (2008) Org. Lett. 10:4429–4432.