Microbial Transformations of Two Beyerane-Type Diterpenes by .

Microbial transformations of two tetracyclic beyerane-type diterpenes, -16β-oxobeyeran-19-oic acid () and its chemical reduction product, -16β-hydroxybeyeran-19-oic acid (), by the filamentous fungus ATCC 8688a yielded eight metabolites (). Incubation of the substrate with afforded three new hydroxylated ones () along with two known ones (-), while incubation of gave three known ones (). The new compounds were characterized by 1D and 2D NMR as well as HRESIMS analysis, and the stereostructures of and were confirmed by X-ray crystallography. The bioreactions were involved not only in stereoselective incorporation of hydroxyl groups at inert positions C-7, -9, -12, and -14 of the two beyerane diterpenes but also in glucosidation at C-19 of . This is the first report on the biotransformation of the diterpenes by using . All compounds were assayed for their α-glucosidase inhibitory, neurotrophic, anti-inflammatory, and phytotoxic activity, and only in neurotrophic assay compounds, and were found to display nerve growth factor-mediated neurite-outgrowth promoting effects in PC12 cells; the others were inactive.