Studies on the Constituents of the Leaves of Pieria japonica D.DON. IV. The Isolation and the Structure of Pieristoxin F, Pieristoxin G and Several Toxic Components

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Abstract
The methanolic extract of the leaves of P. japonica was purified and the final extract was submitted to column chromatography from which pieristoxin-F, pieristoxin-G, deacylpieristoxin-B, pieristoxin-C, asebotoxin-I, grayanotoxin-II and the main poisonous principle, grayanotoxin-III (2.7 g, 0.013% yield), were isolated. Hydrolysis of pieristoxin-F yielded 7-hydroxygrayanotoxin-III. The NMR spectrum of pierisotoxin-F indicated the presence of one O-acetyl and one O-propionyl group, and partial structures of .tbd.CCH(OR)CH(OH)C.tbd. and .sbd.CHOR. Pieristoxin-F is not oxidized by sodium periodate, and its acetate does not agree with tetraacetylasebotoxin-IV. The structure of pieristoxin-F was presumed to be 6-acetyl-7-hydroxy-14-propionylgrayanotoxin-III. The composition of pieristoxin-G was C20H32O8.cntdot.H2O from its elemental analytical values and high resolution mass spectrometry, while its IR spectrum did not show absorptions for carbonyl and unsaturated bond(s). Pieristoxin-G is reduced by lithium aluminum hydride and consumes sodium periodate. Its NMR spectrum indicated the presence of a partial structure of .tbd.CCH(OH)CH(OH)C.tbd. and an epoxide ring. These facts suggested the structure of pieristoxin-G as 7,9-dihydroxy-2,3-epoxygranotoxin-III.

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