Two iron-regulated compounds have been found in acidified ethyl acetate extracts from culture supernatants of Pseudomonas aeruginosa and Pseudumonas cepucia type-strains. Synthesis of both compounds paralleled irondeficient growth, and was repressed in the presence of 100 p~-FeCl,. Yields of these substances varied among different strains and attained maximum levels during stationary phase. Thin layer chromatographic analysis in five different solvent systems revealed that the slower-moving compound chromatographed as two distinct bands, and showed R, values and spectral properties similar to pyochelin. The faster-moving compound co-migrated as a single band with a standard of commercial salicylic acid in each of the chromatographic systems tested. Moreover, a molecule with an identical R, was also produced by Pseudomonscs JIELorescens CHA401, which is known to synthesize salicylic acid as the only siderophore during iron-limited growth. Spectrophotometric and spectrofluorometric titrations led to the identification of this iron-regulated compound as salicylic acid, in agreement with the structure deduced from 'H-NMR and mass spectroscopy. The identity of the P. cepacia siderophore azurechelin as salicylic acid was also conclusively demonstrated. Salicylic acid, like pyochelin and pyoverdin, promoted P. aeruginosa growth in an iron-depleted medium. These results are consistent with a putative siderophore activity for salicylic acid, i.e. azurechelin, as has been demonstrated for P. ueruginossc, P. fluorescens and P. cepacia, Thus, salicylic acid is likely to act as a siderophore in more than one species belonging to the genus Pseudomonas.

Secondary metabolite isolation and analysis of Plumbago europaea L. (Plumbaginaceae) is the aim of this work, which is included in a project of our groups on spontaneous and endemic Sardinian species. Plumbago europaea is the only specie of the genera that grows wild in Italy. Metabolites from leaves and roots of this specie were compared. Moreover, at present, literature on the phytochemical characterisation of P. europaea is poor. Plumbagin was isolated in both of the samples analysed, confirming its nature in the Plumbaginaceae family as chemotaxonomic marker of the Plumbaginae tribe. In this work, hydroplumbagin-4-O-glucoside and myricetin-3-O-rhamnoside are isolated for the first time in the genus.

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