Diterpene Alkaloid Karacoline from Taxus baccata Growing in Georgia

Abstract

The plant Taxus baccata L. (Taxaceae) is known as a source of the alkaloid taxol, which exhibits antitumor properties [1]. It is broadly distributed in the western regions of Georgia. The in vitro pharmacological activity of the alkaloid fraction enriched in taxol that was obtained by us from the aerial parts of T. baccata was studied in various dilutions for cultured tumor cells A-549 (lung carcinoma), DLD-1 (rectal adenocarcinoma), and WS-1 (fibroblastoma) in the Basic Sciences Department, University of Quebec in Chicoutimi, Canada. Inhibition by 50% was demonstrated for cultured tumor cells A-549, DLD-1, and WS-1 at dilutions 18.5 ± 0.8 g/mL and 8 ± 1 g/mL (A-549), 58 ± 10 g/mL and 15 ± 2 g/mL (DLD-1), and 36 ± 7 g/mL (WS-1) [2]. The goal of our investigation was to study further the chemistry of the alkaloid-containing fraction isolated by us. Analysis of this fraction showed that taxol was accompanied by an alkaloid that had the same mobility as an analogous component in the commercial preparation. Separation over a column of silica gel with elution by CHCl3 and CHCl3:MeOH (1–20%) isolated crystalline base A3, mp 185–187°C (CHCl3:MeOH). The base isolated by us was identified based on spectral data (PMR and 13C NMR) and comparison with the literature as the known alkaloid karacoline, which was obtained previously from Aconitum karacolicum [3, 4]. PMR spectrum (CDCl3, , ppm): 0.85 (3H, s, N–CH2–CH3), 1.055 (3H, m, N–CH2–CH3), 3.5 (3H, s, 16-OCH3), 4.0 (1H, m, H-14). 13C NMR spectrum (CDCl3, , ppm): 71.480 (C-1), 29.373 (C-2), 31.298 (C-3), 32.317 (C-4), 46.072 (C-5), 24.950 (C-6), 44.539 (C-7), 73.385 (C-8), 46.109 (C-9), 39.993 (C-10), 48.475 (C-11), 29.445 (C-12), 43.828 (C-13), 74.485 (C-14), 41.789 (C-15), 82.388 (C-16), 61.955 (C-17), 27.099 (C-18), 59.650 (C-19), 12.595 (N–CH2–CH3). The diterpene alkaloid karacoline was isolated for the first time from T. baccata. We also studied the accumulation dynamics of the taxol fraction according to vegetation phases of T. baccata collected in various habitats: