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The biotransformation of three prominent macrolide antibiotics (azithromycin, clarithromycin and erythromycin) by an activated sludge culture, which was adapted to high concentrations of azithromycin (10 mg/L) was investigated. The study included determination of removal kinetics of the parent compounds, identification of their major biotransformation products (TPs) and assessment of ecotoxicological effects of biotransformation. The chemical analyses were performed by ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry, which enabled a tentative identification of TPs formed during the experiments. The ecotoxicological evaluation included two end-points, residual antibiotic activity and toxicity to freshwater algae. The enriched activated sludge culture was capable of degrading all studied macrolide compounds with high removal efficiencies (>99%) of the parent compounds at elevated concentrations (10 mg/L). The elimination of all three macrolide antibiotics was associated with the formation of different TPs, including several novel compounds previously unreported in the literature. Some of the TPs were rather abundant and contributed significantly to the overall mass balance at the end of the biodegradation experiments. Biodegradation of all investigated macrolides was associated with a pronounced reduction of the residual antibiotic activity and algal toxicity, indicating a rather positive ecotoxicological outcome of the biotransformation processes achieved by the enriched sludge culture.

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To establish a universal analytical tool that could be used as a bioactive quality determination procedure on medicinal plant extracts, a range of spectrophotometric assays, HPLC, near infrared reflectance spectroscopy and chemometric analysis were employed for determination of the bioactive quality of 16 widely spread medicinal plants. Macro-constituents (total carbohydrates, soluble polysaccharides, proteins, amino acids) and secondary plant metabolites (total phenols, flavonoids, hydroxycinnamic acids, flavons, and flavonols) were determined, and HPLC method for the simultaneous determination of phenolic acids and flavonoids was developed, and its linearity, limits of detection and quantification, precision, and accuracy were validated. The evaluated medicinal plant extracts were characterised by a marked protein (marigold-4.22 g/kg dw), amino acid (marigold-61.14 g/kg dw), and carbohydrate content (dandelion-113.5 g/kg dw), while Lamiaceae plants were distinguished as the predominant sources of polyphenolic bioactives (<2.26 g GAE/L). The developed HPLC method enabled separation of 24 polyphenolic compounds within a short analysis time (30 min) and revealed rosmarinic and chicoric acids as the prevalent polyphenolic constituents. NIR spectroscopy coupled with chemometric analysis of all determined analytical parameters indicated the suitability of NIR analysis for amino acids, carbohydrates, and polyphenols determination in medicinal plant extracts.