Investigations of Medicinal Plants of Euphorbiaceae and Thymelaeaceae Occurring and Used in Thailand; II. Cryptic Irritants of the Diterpene Ester Type from Three Excoecaria species [1]

Abstract

From leaves of E. oppositifolia the irritant Excoecaria factor O₁ was isolated. Its structure 1 was shown to be identical with that of a factor obtained by transesterification of the cryptic Excoecaria factor group O^′ _z from the latex of the plant. From the non-irritant ethyl acetate fractions of the latices of E. agallocha, E. oppositifolia and E. bicolor, three TLC-homogenous non-irritant mixtures A^′ _z, O^′ _z and B^′ _z were isolated and shown to represent non-separable cryptic Excoecaria factor groups containing 9,13,14-orthoesters of 5β-hydroxyresiniferonol esterified in 20-position. The mixtures may be activated by mild treatment with sodium methoxide to generate mixtures of highly irritant factor groups A_z, O_z and B_z together with mixtures of aliphatic acid methylesters. The former may be separated partially by reversed phase TLC and yielded Excoecaria factors O₁, O₂, A₃, B₃ and B₄ together with residual non-separable factor groups. The structures 1-5 of the individual daphnane type irritant Excoecaria factors were elucidated by spectroscopic means. Their irritant activities were determined quantitatively on the mouse ear. The mixtures of methyl esters of aliphatic acids were analyzed by GC. Thus the complete structures of the cryptic factor groups from latex were deduced.

1 I. Comm. see loc cit. 1

1 I. Comm. see loc cit. 1