J Chromatogr A, 1647, 462154 (2021). Hydromethanolic extracts of Cinnamomum verum and C. cassia (Lauraceae) were separated on MS-grade HPTLC silica gel (prewashed twice with methanol – water 4:1 and dried at 110 °C for 20 min) with toluene – ethyl acetate – methanol 6:3:1. Residual organic solvent was removed by drying under automated cold stream air for 20 min. Chromatograms were documented under white light, UV 254 nm and for fluorescence detection at 366 nm, and afterwards submitted to Aliivibrio fischeri bioassay: 2 mL of bacterial suspension were piezoelectrically sprayed on the plate and bioluminescence was measured every 3 min for 30 min (120 s exposure time). For the first time, analytes from a bioactive zone, isolated by the oval elution head of a TLC-MS interface pump, were trapped from the highly salted layer by a heart-cut elution (45 s, flow rate 0.1 mL/min) through a biocompatible in-line filter to different on-line desalting devices. Using a two-position switching valve, the desalted analytes were guided to a reverse-phase UPLC column and separated at 40 °C using a fast gradient (ca. 13 min, 0.6 mL/min) with methanol (from 2 - 90 %) and an ammonium acetate solution (2.5 mM, pH 4.5 adjusted with acetic acid). After HPLC separation, analytes were detected by photodiode array (PDA) and then ESI-MS in polarity switching mode (cone voltage of 10 V, ESI probe at 600 °C, ESI source at 120 °C). Identified active compounds were cinnamic acid, coumarin, as well as the in HPTLC coeluting cinnamaldehyde and 2-methoxycinnamaldehyde. Separately, proof-of-concept tests were also made for more polar phenolic acids (gallic, chlorogenic, caffeic, cinnamic, ferulic and coumaric acids) but without HPTLC separation.

CBS 125. HPTLC of estrogen-active compounds in a migrate of a food contact material on silica gel with chloroform - acetone - petroleum ether 11:4:5. Planar Yeast Estrogen Test (P-YES) was performed by spraying 2 mL yeast cells onto HPTLC plates, followed by incubation at 30 °C for 3 h and spraying with 2 mL 0.5 mg/mL 4-methylumbelliferyl-beta-D-galactopyranoside and incubation for 20 min at 37 °C. The method was compared with microtiter bioassay (L-YES). P-YES was more sensitive than L-YES and results can be repeated upto one year later.

Sens. Actuators B Chem. 299, 126902 (2019). Thin layer chromatography combined with surface-enhanced Raman spectroscopy (TLC-SERS) of melamine in milk on silica gel with acetone - chloroform - ammonia 14:1:4. 2 μL gold nanoparticles were drop casted onto the analyte spot, followed by measurement using a  Raman spectrometer equipped with a diode laser emitting at 785 nm wavelength for illumination over a 100 μm diameter was used to obtain the SERS signals. A parallel representation model of the triple-spectral data was constructed using a pure quaternion matrix. Quaternion principal component analysis (QPCA) was utilized to build a quantitative model using support vector regression (SVR) algorithm. The method allowed the determination of melamine-contaminated milk with concentrations from 1 to 250 ppm.

Food Chem. 334, 127562 (2021). HPTLC of five seaweed cultivars, namely three Saccharina japonica and two Undaria pinnatifida on silica gel with n-hexane - ethyl acetate - formic acid 30:50:1. Detection by spraying with anisaldehyde sulfuric acid reagent (1.5 mL of anisaldehyde was mixed with 210 mL of ethanol, 25 mL acetic acid and 13 mL conc. sulfuric acid), followed by heating at 120 °C for 3 min. Qualitative identification under UV light at 366 nm. HPTLC-bioautography antimicrobial assays by dipping into B. subtilis cell suspension, followed by incubation at 37 °C for 30 min and E. coli suspension, followed by incubation at 37 °C for 1 h. Visualization by dipping into a solution of MTT dye with triton X-100 (1 mg/mL). Stearidonic, eicosapentaenoic, and arachidonic acids were identified by HPLC-MS.

Front. Pharmacol. 12, 755941 (2021). High-throughput eight-dimensional (8D) hyphenation of normal-phase HPTLC with multi-imaging by ultraviolet, visible and fluorescence light detection as well as effect-directed assay and heart-cut of the bioactive zone to orthogonal reversed-phase high-performance liquid chromatography-photodiode array detection-heated electrospray ionization mass spectrometry. The method allowed the analysis of 68 powdered plant extracts (botanicals) which are added to food products in food industry and the study of antibacterials, estrogens, antiestrogens, androgens, and antiandrogens, as well as acetylcholinesterase, butyrylcholinesterase, α-amylase, α-glucosidase, β-glucosidase, β-glucuronidase, and tyrosinase inhibitors in an array of 1,292 profiles.

Food Chem. 374, 131714 (2022). HPTLC of authentic samples (7 apricot and 5 pumpkin samples) and simulated adulterated products on silica gel with methanol - ethyl acetate - n-hexane 170:40:3. Fluorescence detection (FLD) at 366 nm. Carotenoids (hRF=18) were identified as chemical markers, being responsible for their differentiation in apricot and most pumpkins extracts. Partial least squares discriminant analysis (PLS-DA) proved to be a promising tool for predicting the amount of added pumpkin down to 2.5 %, with prediction errors as low as 20 %.

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.

Talanta 223 (2021) 121701. Development of workflow for a bioanalytical multi-imaging screening based on HPTLC-UV/Vis/FLD-EDA-HESI-HRMS and application to 54 bark, leaf and seed extracts of Sri Lankan Abelmoschus moschatus (abelmosk) to find out the most bioactive individual compounds. HPTLC on silica gel with toluene - ethyl acetate - methanol 6:5:2 or toluene - ethyl acetate 7:3 up to 65 mm, evaluation in (A) UV 254 nm, (B) white light, (C) fluorescence 366 nm, and after derivatization with (D) primuline reagent at UV 366 nm, (E) p-anisaldehyde sulfuric acid reagent, (F) vanillin sulfuric acid reagent, (G) p-aminobenzoic acid reagent, (H) the latter in fluorescence evaluation at 366 nm, (I) diphenylamine aniline orthophosphoric acid reagent, (J) ninhydrin reagent, (K) Fast Blue B salt reagent. For (E-K) detection in white light after heating at 140°C for 5 min, and (L) natural product reagent in fluorescence 366 nm after air-drying. For effect-directed profiling, HPTLC on plates prewashed with methanol - water 3:1, drying for 15 min and immersing in the respective assay solution/suspension or spraying with it, then incubating, drying and evaluation in white light (A) for Gram-negative Aliivibrio fischeri bioassay, spraying the bacterial culture onto the chromatogram and recording the instant bioluminescence over a 30 min period with the positive controls of caffeine; (B) for Gram-positive Bacillus subtilis bioassay, dipping the chromatogram in the bacterial suspension for incubation at 37°C for 2 h, then dipping into a 0.2 % PBS-buffered MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide) solution with positive control tetracycline; (C) for α-glucosidase inhibition assay, spraying with substrate solution, drying, pre-wetting and incubation by spraying with Fast Blue B salt solution with positive control acarbose, absorbance measurement at 546 nm and quantification via peak area; (D) for β-glucosidase inhibition assay, analog to (C), but using β-glucosidase and 2-naphthyl-β-D-glucopyranoside and longer incubation time, with positive control imidazole; (E) for tyrosinase inhibition assay, spraying with substrate solution, after drying with tyrosinase solution, incubated and dried with positive control kojic acid, absorbance measurement at 579 nm; (F) for radical-scavenging assay, immersing the chromatogram into 0.02 % methanolic 2,2-diphenyl-1-picrylhydrazyl solution, air-dried with the positive control ascorbic acid. The workflow provided comprehensive information about multi-potent compounds and sample diversity, which is elementary for product quality control in the field of botanicals, foods and medicinal plants.