In vitro assessment of pediococci- and lactobacilli-induced cholesterol-lowering effect using digitally enhanced high-performance thin-layer chromatography and confocal microscopy.

The cholesterol-lowering properties of 12 lactic acid bacteria (LAB) in the absence or presence of 0.3% bile salts were assessed and compared quantitatively and qualitatively in vitro. A new, more sensitive and cost-effective high-performance thin-layer chromatography method combined with digital image evaluation of derivatised chromatographic plates was developed and validated to quantify cholesterol in LAB culture media. The performance of the method was compared with that of the o-phthalaldehyde method. For qualitative assessment, assimilated fluorescently tagged cholesterol was visualised by confocal microscopy. All LAB strains exhibited a cholesterol-lowering effect of various degrees (19-59% in the absence and 14-69% in the presence of bile salts). Lactobacillus plantarum LAB12 and Pentosaceus pentosaceus LAB6 were the two best strains of lactobacilli and pediococci. They lowered cholesterol levels by 59% and 54%, respectively, in the absence and by 69% and 58%, respectively, in the presence of bile salts. Confocal microscopy showed that cholesterol was localised at the outermost cell membranes of LAB12 and LAB6. The present findings warrant in-depth in vivo study. Graphical abstract (A) 3D plots based on scan at 525 nm of (B) derivatized HPTLC plate of separated cholesterol and (C) confocal microscopic image showing the localisation of NBD-cholesterol assimilated by LAB.