Trends Anal. Chem. 168, 117362 (2023). Review of functional and non-functional assays in the study of acetylcholinesterase (AChE) ligand discovery, including HPTLC for the assessing of AChE inhibition and for monitoring of ChE activity.

3 Biotech 13, 32 (2023). Samples were the products of transgalactosylation operated by β-galactosidase immobilized on modified carrageenan beads in a solution of lactose. Raffinose, a trisaccharide, was used as standard. TLC on silica gel with n-propanol – water 17:3. Detection of galacto-oligosaccharides by spraying naphthol reagent (50 mg α-naphtol in 95 mL ethanol and 5 mL sulfuric acid), followed by heating. The target zones from unsprayed layers were further extracted with methanol using a TLC-MS interface into a quadrupole MS (flow rate 0.2ml/min, positive and negative electrospray ionization (ESI), m/z range 10–1200). Galactose oligomers were found, from trimers to hexamers (heptamers were observed when the reaction time was beyond 3 hours).

Anal. Methods. 11, 4939-4945 (2019). HPTLC of Peganum harmala seeds on silica gel with ethyl acetate - methanol - ammonia (25%) 85:11:4. Detection under UV light at 254 and 366 nm. Track pattern application by applying each reference compound solution (physostigmine: 0.1–1.5 ng/zone; rivastigmine tartrate and piperine: 200–2000 ng/zone). A new piezoelectric spraying workflow was applied for the HPTLC-enzyme assay: the plate was sprayed with the enzyme solution (6.6 units per mL AChE or 3.3 units per mL BChE), followed by incubation at 37 °C for 25 min and spraying with 0.5 mL substrate-chromogenic solution and drying. The enzyme inhibition densitograms of both assays were measured by inverse scan at 546 nm using a mercury lamp. Equivalency of the AChE/BChE inhibition was calculated for two quantitative modes: applied and developed. A higher accuracy was obtained via an appropriate co-developed reference inhibitor for the enzyme inhibition equivalency calculation. 

J. Planar Chromatogr. 34, 561-567 (2021). HPTLC of Ecuadorian Chenopodium quinoa Willd. leaf extracts on silica gel with formic acid - water - methyl ethyl ketone - ethyl acetate 1:2:4:3. Detection by heating at 105 °C for 60 min, followed by a three step derivatization method: 1) spraying with a 3 mL solution of α-amylase (5 U/mL of α-amylase in ethanol 10 %), followed by incubation at 37 °C for 30 min, 2) a 2 mL solution of starch (1 % of starch in ethanol 10 %) was applied on the plate, followed by incubation at 37 °C for 10 min, and (3) detection using iodine vapors for 2 min (1 g of solid iodine). The method allowed rapid localizing of α-amylase inhibitory compounds in complex plant matrices.

J. Planar Chromatogr. 33, 263-269 (2020). HPTLC of the interaction between methylene blue and purified glutathione-S-transferase (5 mmol/L methylene blue and enzyme solution in 0.1 mol/L potassium phosphate buffer) on silica gel with butanol - acetic acid - water 12:3:5 for 2 h. Detection by spraying with ninhydrin (0.25 % in acetone). The complex that most likely came from the interaction of methylene blue and purified glutathione-S-transferase had a hRf of 16.

J. Sep. Sci. 43, 2477-2486 (2020). HPTLC of urea produced by arginase as a bioautographic method for the detection of arginase inhibitors in Myrtus communis on silica gel with ethyl acetate - methanol - water - formic acid 800:100:100:1. Detection by spraying with arginase solution (50 U in 3 mL of a buffer containing Tris–HCl 50 mM, pH 7.5 and 0.1 % of BSA), followed by spraying with 3 mL of L-arginine solution (200 mM, pH 9.7) and incubation at 37 ºC for 60 min. Visualization by spraying with 3 mL of sulfuric acid - phosphoric acid - water 2:7:91 and 2 mL of alpha-isonitrosopropiophenone solution (5% in absolute ethanol) followed by heating at 100 ºC for 1h. The hRF value for the inhibitor N-trans-caffeoyltyramine was 27. Sensitiviy was estimated for the arginase inhibitor Nω-hydroxy-nor-Arginine (nor-NOHA), resulting in a LOD of 0.1 µg/zone.

Phytochem. Anal. 30, 679-686(2019). HPTLC-Acetylcholinesterase bioassay of cherimoya fruits on silica gel with the enzyme substrate 1‐naphthyl acetate (1.5 mg/mL). Enzymatic solution was sprayed (1 U/mL in 50 mM Tris–HCl buffers at pH 7.8), followed by incubation at 37 ºC for 10 min. A Fast Blue B salt aqueous solution (1.0 mg/mL), freshly prepared, was sprayed onto the plate to obtain a purple background. Further analysis by HPTLC-MS allowed the characterization of three potential AChE inhibitors: anonaine, glaucine and xylopine.

Phytochem. Anal. 28, 74-86 (2017). Review of the latest developments and applications in the field of bioautographic enzyme analysis and assays including acetylcholinesterase, dipeptidyl peptidase 4, glucosidase, lipase, xanthine oxidase, glucose-6-phosphate-dehydrogenase, phosphoglucose isomerase and tyrosinase.