Bioactive potential of marine <i>Aspergillus niger</i> AMG31: Metabolite profiling and green synthesis of copper/zinc oxide nanocomposites – An insight into biomedical applications

Abstract This investigation explored marine fungi from Red Sea sediments, focusing on Aspergillus niger AMG31. Chemical profiling of the fungal extract by high-performance liquid chromatography and gas chromatography–mass spectrometry revealed diverse bioactive compounds, with hesperetin (80,471.56 μg·g −1 ) and rosmarinic acid (8,396.08 μg·g −1 ) predominating. Additionally, the extract contained substantial phenolics (55.517 mg·g −1 ), flavonoids (28.757 mg·g −1 ), and tannins (18.650 mg·g −1 ). The fungal extract facilitated green synthesis of copper-zinc oxide nanocomposites (CZ nanocomposites), which were thoroughly characterized using fourier transform infrared spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, dynamic light scattering, and zeta potential. The physicochemical characterization exhibits the formation of spherical, well-arranged, crystalline structures, with sizes of 12–45 nm. The nanocomposites demonstrated exceptional hemocompatibility (1.7% hemolysis at 1,000 μg·mL −1 ). Antioxidant evaluations showed potent activity in both the extract (2,2-diphenyl-1-picrylhydrazyl [DPPH] IC 50 : 25.66 μg·mL −1 ; 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) [ABTS] IC 50 : 33.36 μg·mL −1 ) and CZ nanocomposite (DPPH IC 50 : 42.71 μg·mL −1 ; ABTS IC 50 : 47.34 μg·mL −1 ), with the nanocomposite exhibiting superior total antioxidant capacity (394.08 AAE μg·mg −1 ) and ferric reducing antioxidant power (362.57 AAE μg·mg −1 ) values. The CZ nanocomposite demonstrated stronger anti-inflammatory activity (COX-1 IC 50 : 22.72 μg·mL −1 ; COX-2 IC 50 : 33.03 μg·mL −1 ) than the extract (COX-1 IC 50 : 205.54 μg·mL −1 ; COX-2 IC 50 : 397.18 μg·mL −1 ). Antimicrobial results revealed that the fungal extract exhibited superior inhibitory zones against Staphylococcus aureus (30 mm), Bacillus subtilis (29 mm), Escherichia coli (30 mm), and Salmonella typhi (25 mm), exceeding gentamicin performance, while the CZ nanocomposite showed exceptional activity against Enterococcus faecalis (32 mm). For Candida species, the nanocomposite demonstrated superior inhibition against Candida albicans (35 mm, minimum inhibitory concentration [MIC] 7.8 μg·mL −1 ), while the extract showed better activity against Candida tropicalis (27 mm, MIC 15.62 μg·mL −1 ). This work highlights the potential of Red Sea fungi as sources of bioactive compounds and green synthesis of functional nanomaterials for pharmaceutical applications.