Biotransformation of oleanonic acid from jujube by food fermentation fungus Actinomucor elegans and the potential anti-neuroinflammatory properties of metabolites.

This study investigated the biotransformation of oleanonic acid (1), a major bioactive constituent of jujube, using Actinomucor elegans, a filamentous fungus commonly employed in food fermentation. The process yielded 12 previously undescribed metabolites (compounds 4, 5, 7, 10, 11, and 14-20), along with seven known compounds. Structural elucidation of these metabolites was conducted through comprehensive spectroscopic analyses. The anti-neuroinflammatory activities of these metabolites were investigated by assessing their ability to inhibit nitric oxide (NO) production in BV-2 microglial cells stimulated by lipopolysaccharide (LPS). Notably, compounds 4, 5, 10, and 13 exhibited greater inhibitory activity compared to oleanonic acid. Among them, compound 10 demonstrated remarkable efficacy, significantly reducing the transcription levels of inflammation-associated factors, including IL-6, IL-1β, COX-2, and TNF-α. Furthermore, compound 10 enhanced autophagy activation by upregulating the expression of Beclin 1 and LC3 II at the protein level, underscoring its possible inflammation-reducing effects.