Compost Tea as a Natural Bioactive Solution: Unlocking the Antimicrobial and Antiviral Potential of Bell Pepper and Citrus Wastes

The growing demand for sustainable medical applications has sparked interest in the valorisation of agro-industrial waste for bioactive compounds. Compost teas (CTs) from agrifood waste, rich in phenolics and lignin derivatives, offer promising biological properties. This study analysed CTs from bell pepper (CT-BP) and citrus (CT-C) composted waste, assessing their antioxidant, antiviral, and antimicrobial activities. NMR spectroscopy and thermochemolysis revealed that CT-BP had more oxidised lignin derivatives, while CT-C contained intact lignin structures. Both CTs effectively inhibited Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis), with CT-BP showing greater efficacy. However, Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were more resistant. CT-BP also exhibited potent antiviral effects against enveloped viruses like herpes simplex virus type 1 (HSV-1) and respiratory syncytial virus (RSV). These findings support the use of compost-derived extracts as sustainable bioactive agents, offering natural alternatives to conventional treatments. Further research could enhance the extraction and scalability of these materials for biomedical applications, aligning with principles of the circular economy.