Planta Med 2014; 80 - P2O32
DOI: 10.1055/s-0034-1395024

Identification of new phorbol ester derivatives in extracts from Croton tiglium L. seeds by UHPLC-MS/MS and the approach of a quantification method after alkaline hydrolysis

J Kummer 1, AK Kiss 2, S Granica 2, MF Melzig 1
  • 1Institute of Pharmacy – Pharmaceutical Biology, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany
  • 2Department of Pharmacognosy and Molecular Basis of Phytotherapy, Faculty of Pharmacy, Medical University of Warsaw, Banacha 1, 02 – 097 Warsaw, Poland

The UHPLC-MS/MS chromatogram of extracts from Croton tiglium L. seeds showed a great diversity of over 100 different signals, in which the characteristic fragmentations of phorbol esters appear. These are the active ingredients, which are known to be tumor-promoting and skin irritating diterpene esters since Hecker et al. discovered TPA (12-O-tetradecanoylphorbol-13-acetate) in the oil of C. tiglium L. seeds [1]. There are around 20 different phorbol esters described in the literature, which are supposed to be the main compounds [2]. We determined a great variety of different combinations of four possible ester groups, which form over 100 different phorbol ester derivatives. These are mostly minor compounds, so they are not accessible for a proper NMR identification, but the fragmentation patterns give adequate information about the esterification. For the quantification of such a broad variety of possible toxic compounds it will be necessary to summarize all phorbol ester derivatives. This could be done by alkaline hydrolysis and the quantification of the resulting basic diterpene alcohols, like phorbol, 4-deoxy-4-α-phorbol and products their epimerization.

References:

1. Hecker, E., Schmidt, R., Phorbolesters – the Irritants and Cocarcinogens of Croton Tiglium L. Prog Chem Org Nat Prod 1974; 31: 377 – 467.

2. Zhang, Xiao-Long, Wang, Lun, Li, Fu, Yu, Kai and Wang, Ming-Kui, Cytotoxic Phorbol Esters of Croton tiglium. Journal of Natural Products 2013; 76: 858 – 864.