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Isolation procedures of two new acylphloroglucinols, myrtucommulone-A and myrtucommulone-B, from Myrtus communis leaves are given. Myrtucommulone-A was highly antibacterial against gram-positive bacteria but was not active against gram negatives. The chemical relation to other acylphloroglucinols and the antibacterial activity of the compounds isolated are discussed.

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The short half-life of aminopenicillin antibiotics in the aquatic environment put to the challenge the detection of their degradation products among environmental hydro-chemists. In a quest to study the occurrence of a new emerging micro-pollutant in the aquatic environment we attempted this by analyzing samples from a wastewater treatment plant for a major degradation product of amoxicillin (i.e., amoxicillin-diketopiperazine-2', 5') using a high-performance liquid chromatography technique coupled with tandem mass spectrometry method. ADP was repeatedly detected in all wastewater and effluent samples (18) from which it was extracted. To the best of our knowledge, this is the first study that evidently proves the occurrence of the chemically stable form of AMX, its Diketopiperazine-2', 5', in wastewater and effluent samples. Furthermore, penicillins are known to cause most allergic drug reactions. There is a risk that residues of hypersensitivity-inducing drugs, such as penicillins and their degradation products, may elicit allergic reactions in human consumers of water and food of animal origin.

Environmental context.Although amoxicillin is a widely used antibiotic, it is yet to be detected in the aquatic environment. This study traces the production of the amoxicillin-S-oxide degradation product, and shows that it is consistently obtained only under sunlight irradiation. This is the first study to demonstrate the formation, under controlled environmental conditions, of this chemically stable product of amoxicillin. Abstract.Amoxicillin (AMX) is a widely used penicillin-type antibiotic, and its presence in the environment has been widely investigated. The formation and structure of an oxidised degradation product (DP) of AMX are described in the present work. The experiments were carried out in buffer solution (pH 7.5) containing AMX at a concentration of 100 μg mL–1, with and without acid and in field secondary effluent. The DP, AMX-S-oxide (sulfoxide), was consistently obtained only under sunlight irradiation and was significantly augmented by the addition of humic acid (5 mg L–1) and mainly in field secondary effluent, which acts as a natural photo-sensitiser. The structure of the AMX-S-oxide DP was determined by an LC-MS technique using a mobile phase of deuterated and non-deuterated solvents. A 1H NMR spectrum was obtained for the pure compound isolated by preparative HPLC. Further confirmation of the AMX-S-oxide structure was achieved by comparison of its UV spectrum with those of the two oxidation products, AMX-S-oxide and hydroxylated AMX, obtained by the ozonolysis of AMX.