Sustainable Processing of Pineapple and Orange Peel Waste: Hydroalcoholic Extracts with Anti-Inflammatory Activity and Cytotoxicity Assessment

Fruit-processing by-products from juice industries, food-service establishments, and canteens are frequently discarded despite their potential as sources of bioactive compounds. Their integrated valorization through the extraction of high-value compounds and recycling of residual biomass can contribute to waste minimisation, resource efficiency, and circular-bioeconomy strategies. At the Lisbon University Centre of Universidade Lusófona, canteen facilities generate an estimated 2,000 kg of fruit-peel waste annually. This study investigated an integrated valorisation approach in which pineapple and orange peels were processed to recover bioactive hydroalcoholic extracts, while the post-extraction biomass was composted and applied to the university’s organic garden.

Pineapple and orange peels were collected, oven-dried at 50°C for 24 h, milled, and sieved through a 0.6-mm mesh. Hydroalcoholic extracts were obtained by Soxhlet extraction for six complete cycles using ethanol/water (70:30, v/v) at a solid-to-solvent ratio of 1:10 (m/v), followed by concentration under reduced pressure using a rotary evaporator. The resulting solid residues were transferred to a composter; after composting, the stabilized material was applied to the university’s organic garden. Cytotoxicity of the extracts was evaluated in HCT116 human colorectal carcinoma cells exposed to 1, 5, and 10 mg/mL for 48 h using the Cell Counting Kit-8 (CCK-8) assay. Anti-inflammatory activity was assessed using a COX-2 inhibitor screening assay (Cayman Chemical; Michigan USA) at 5 and 10 mg/mL.

Results showed low cytotoxicity for both extracts, with cell viability above 84% at all concentrations tested. COX-2 inhibition increased with concentration, ranging from approximately 50–61% at 5 mg/mL to 77–88% at 10 mg/mL. Pineapple peel extract showed the highest inhibitory activity, reaching approximately 88% COX-2 inhibition at 10 mg/mL. These preliminary findings demonstrate the feasibility of an integrated, campus-based circular process combining the recovery of potentially bioactive extracts with the composting and agricultural reuse of the remaining biomass.