Biotransformation of α-asarone by Alternaria longipes CGMCC 3.2875

Biotransformation of α-asarone by Alternaria longipes CGMCC 3.2875 yielded two pairs of new neolignans, (+) (7S, 8S, 7′S, 8′R) iso-magnosalicin ( 1a )/(−) (7R, 8R, 7'R, 8′S) iso-magnosalicin ( 1b ) and (+) (7R, 8R, 7′S, 8'R) magnosalicin ( 2a )/(−) (7S, 8S, 7′R, 8'S) magnosalicin ( 2b ), and four known metabolites, (±) acoraminol A ( 3 ), (±) acoraminol B ( 4 ), asaraldehyde ( 5 ), and 2, 4, 5-trimethoxybenzoic acid ( 6 ). Their structures, including absolute configurations, were determined by extensive analysis of NMR spectra, X-ray crystallography, and quantum chemical ECD calculations. The cytotoxic activity and Aβ₄₂ aggregation inhibitory activity of all the compounds were evaluated. Compound 2 displayed significant anti-Aβ₄₂ aggregation activity with an inhibitory rate of 60.81% (the positive control EGCG: 69.17%). In addition, the biotransformation pathway of α-asarone by Alternaria longipes CGMCC 3.2875 was proposed.