Brassicasterol is a phytosterol found in canola and rapeseed oils, marine algae, and shellfish.[1] It inhibits recombinant sterol Δ24-reductase with a Ki value of 42.7 μM in vitro. Brassicasterol increases accumulation of demosterol, a cholesterol precursor and substrate of sterol Δ24-reductase, and inhibits cholesterol formation in HL-60 cells in a dose-dependent manner. It also inhibits the hemolytic activity of pneumolysin from S. pneumoniae without affecting bacterial growth at concentrations up to 1,000 μg/ml.[2]

Reference:
[1]. Fernández, C., Suárez, Y., Ferruelo, A.J., et al. Inhibition of cholesterol biosynthesis by Δ22-unsaturated phytosterols via competitive inhibition of sterol Δ24-reductase in mammalian cells Biochem. J. 366(Pt 1), 109-119 (2002).
[2]. Li, H., Zhao, X., Deng, X., et al. Insights into structure and activity of natural compound inhibitors of pneumolysin Sci. Rep. 7:42015, (2017).