The alkamide constituents of Zanthoxylum rhetsa (Roxb.) DC. fruits

Alkamides, a class of lipophilic protoalkaloids or pseudoalkaloids, have been drawing attention of scientists due to their diverse pharmacological activities [1], [2]. Zanthoxylum species, frequently used in Asian cuisine e.g. Sichuan pepper for their tingling sensation [3], have been well documented to be a rich source of alkamides. Zanthoxylum rhetsa (Roxb.) DC., Rutaceae, originating in subtropical regions, a typical spice and “the soul” of Northern Vietnamese culinary art, is traditionally employed for treatment of inflammatory-related ailments especially toothache [4]. The target of this study was to investigate the alkamide compositions of this spice. From the dichloromethane fraction of the Z. rhetsa fruit extract, fourteen alkamides could be isolated. Two compounds, rhetsamide A and rhetsamide B, were identified as C12 fatty acid isobutylhydroxyamides. The remaining twelve compounds which comprise rhetsamide C-J, zanthoamides G-I and the known sanshool derivatives hydroxy-ζ-sanshool, hydroxy-γ-sanshool, hydroxy-γ-isosanshool, the major compounds of the investigated extract, were determined as C14 fatty acid isobutylhydroxyamides. To our knowledge, none of these compounds except for hydroxy-γ-isosanshool was previously described for this species and this is the first report of the ten new compounds, rhetsamide A-J. These results revealed that the fruits of this plant are a valuable source of new natural products as well as promising biological principles, which are worthy to be further investigated and exploited.

• References

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