Fermented Hylocereus undatus Peel Extract with Enhanced Antioxidant, Anti-Inflammatory, Anti-Biofilm and Sun Protection Potential

Optimal conditions for Aspergillus niger solid-state fermentation (SSF) and post-SSF extraction were determined to effectively increase the bioactive values of dragon fruit peel extract (DFPE). The presence of mycotoxin and mechanistic action of SSF-mediated valorization was also investigated.

Response surface methodology was utilized for optimization. Polyphenol content and presence of mycotoxins was determined by high-performance liquid chromatography. Antioxidant activity was evaluated by DPPH, ABTS and FRAP assays. Anti-inflammatory activity was assessed by heat-induced hemolysis, protein denaturation and protease inhibition. Antibacterial activity was examined via inhibition of bacterial growth and survival, anti-biofilm capacity and synergistic effect with antibiotics. The sun protection potential was evaluated based on the sun protection factor.

Optimal conditions for SSF and post-SSF extraction were identified. After SSF, there were increased levels of catechin, rutin and quercetin with undetectable levels of mycotoxin. In addition, the plausible biochemical mechanism for SSF-mediated total phenolic content enhancement was revealed. In terms of biological activities, fermented DFPE possessed remarkably higher antioxidant, anti-inflammatory, antibacterial and sun protection potential compared to unfermented DFPE.

The bioactive content of DFPE was dramatically boosted by SSF with prospects in food, pharmaceutical and cosmetic applications.