New 30-norlupane derivatives through chemical-microbial semi-synthesis of betulinic acid and their neuroprotective effect.

In this study, seven 30-norlupane derivatives (2-8) wasobtained from the chemical oxidation ofbetulinic acidfollowed bybiotransformationviaBacillus megateriumCGMCC 1.1741. And metabolites 2-4 and 6-8 were newly identified products. In the first step, betulinic acid was chemically oxidizedto platanic acid (1). Following the chemical oxidation, B. megaterium catalyzed the hydroxylation at C-7, C-11, C-15 and C-23 of platanic acid (1) as well as the oxidation of C-3 hydroxyl group. Compared to the labor-intensive isolation from natural plants, this chemical-microbial semi-synthesis is more capable to provide increased structural diversity of oxygenated 30-norlupane. Finally, the potential neuroprotective effect of the derivatives was assessed on neuron-like PC12 cells induced by cobalt chloride (CoCl). Metabolite 6 showed a potent neuroprotective activity.