Planta Med 1994; 60(4): 351-355
DOI: 10.1055/s-2006-959499

© Georg Thieme Verlag Stuttgart · New York

Cryptic and Free Skin Irritants of the Daphnane and Tigliane Types in Latex of Excoecaria agallocha 1

C. Karalai2 , P. Wiriyachitra3 , H. J. Opferkuch4 , 5 , E. Hecker4
  • 2Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Province of Songkhla, Thailand
  • 3Research Centre for National Products, Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand
  • 4Deutsches Krebsforschungszentrum (DKFZ), Division Mechanisms of Tumorigenesis, Research Program 3: Risk Factors of Cancer and Cancer Prevention, Im Neuenheimer Feld 280, D-69009 Heidelberg, Federal Republic of Germany
  • 5Abt. FC-AS, Boehringer GmbH, Sandhofer Str. 116, D-68305 Mannheim, Federal Republic of Germany
1 Part III in the series “Medicinal Plants of Euphorbiaceae Occurring and Utilized in Thailand”. For part II, see Ref. (1)
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Publication Date:
04 January 2007 (online)


In the extremely skin irritant and caustic latex of Excoecaria agallocha the major part of the polyfunctional diterpene esters (DTE) (group I) are aliphatic polyunsaturated 9,13,14-orthoesters of the daphnane-type parent alcohol 5β-hydroxyresiniferonol-6α,7α-epoxide, esterified simultaneously in their 20-positions with aliphatic saturated homologous n-carboxylic acids (even numbered, C22-C30). The minor part of DTE is composed of analogous structures of 5β,12β-dihydroxyresiniferonol-6α,7α-epoxide (group II) and of aliphatic 13-polyunsaturated, 20-saturated diesters of the tigliane-type parent alcohol 12-deoxyphorbol (group III). All three groups of DTE exhibit practically no irritant activity on the mouse ear. By alkaline transesterification of groups I-III, the corresponding highly irritant multicomponent mixtures of Excoecaria factors A (OH-20 deacylated) are released. They comprise a mixture of the known Excoecaria factors A1/A2/A3 and three mixtures of hitherto unknown Excoecaria factors A4/A5, A6/A7 and A8/A9. The groups I-III are typical structures of “cryptic irritants”. By an alternative, extremely mild separation procedure the highly irritant mixture A1/A2/A3 was obtained directly. It represents the “free” Excoecaria factors, the natural constituents of the latex responsible for its bioactivity.