Background: Citrullus colocynthis L. (C. colocynthis) is commonly known as colocynth. It belongs to the family Cucurbitaceae that is frequently used in alternative medicine in the north of Africa. The aim of the study: the present research was undertaken to investigate the chemical composition, antioxidant, antiproliferative, and antibacterial potentials of C. colocynthis seed extract. Material and methods: the chemical composition of C. colocynthis seed organic extract was characterized using gas chromatography/mass spectrometry (GC-MS). The antioxidant property was carried out using both β-carotene bleaching and DPPH assays. The antibacterial effect was effectuated using the agar disc diffusion method. The antiproliferative activity vs. human colorectal adenocarcinoma cell line (HT-29) and human breast adenocarcinoma cell line (MDA MB 231) were carried by WST-1 test. The chemical analysis showed the presence of interesting potentially bioactive compounds. The studied plant extract exhibited antioxidant potential with IC₅₀ value of 2. 22 mg/mL (β-carotene bleaching) and 8.98 ± 0.619 mg/mL (DPPH). Concerning the antiproliferative activity, the seed extract was effective in MDA-MB-231 and HT-29 cancer cells with IC₅₀ values 86.89 ± 3.395 and 242.1 ± 17.9 μg/mL, respectively, whilst the extract of Citrullus colocynthis seeds was non-toxic in healthy human dermal fibroblasts. Regarding the antibacterial test, the extract was effective in Gram-positive bacteria only. Conclusion: The outcome of this research indicated that the extracts from C. colocynthis seeds may compose a promising source with interesting compounds that can be used to fight cancer, free radicals damage, and bacterial infections.

Azo dyes are widely used in industries and their release in the environment contributes to the pollution of effluents. The authors aim to develop a new eco‐friendly water treatment method for the degradation of azo dyes based on in situ magnetic separation and immobilisation of bacterial cells. The immobilisation was achieved using superparamagnetic Fe ₃ O ₄ nanoparticles and offers the possibility of reusing bacteria by magnetic separation for several degradation cycles. The iron – oxide nanoparticles were synthesised by reverse co‐precipitation. The Gram‐positive bacteria Bacillus subtilis were immobilised using iron–oxide nanoparticles by adsorption and then separated with an external magnetic field. Transmission electron microscopy observation showed that the particles' diameter was ∼20 nm with a narrow size distribution. Moreover, the iron–oxide nanoparticles were adsorbed onto the surface in order to coat the cells. B. subtilis has proved its ability to decolorise and degrade several azo dyes at different values of pH, with the highest decolorisation rate for Congo red. Furthermore, immobilised cells have a degradation activity similar to that of free cells. The system provided a degradation rate up to 80% and could be reused for seven batch cycles.