J. Ethnopharmacol. 213, 230-255 (2018). Review of the botany, ethnopharmacology, phytochemistry, biological activities, nutritional value, possible molecular mechanisms, safety and clinical applications of Morinda officinalis with a special focus on its bioactivities, including the application of HPTLC for the analysis of oligosaccharides from different habitats.

Food Chem. 243, 258-268 (2018). HPTLC of [6]-gingerol (1) and [6]-shogaol (2) in 17 ginger rhizomes and ginger-containing food products on silica gel with n-hexane – ethyl acetate 13:7. Detection by dipping into anisaldehyde sulfuric acid reagent (5 mL concentrated sulfuric acid was added to a mixture of 500 μL anisaldehyde, 10 mL acetic acid and 100 mL methanol), followed by heating at 110 °C for 5 min. Quantitative determination by absorbance measurement at 580 nm. The hRF values for (1) and (2) were 32 and 41, respectively. LOD and LOQ were 25 and 45 ng/zone for (1) and 20 and 40 ng/zone for (2), respectively. The primuline reagent (100 mg primuline in 200 mL acetone – water 4:1) was also investigated for detection, but it was not as sensitive. Polynomial calibrations ranged between 0.9982 and 0.9999. Their contents ranged 0.2–7.4 mg/g (1) and 0.2–3.0 mg/g (2) in the different products. Intermediate precisions were mostly ≤8 % for (1) and ≤10 % for (2) in the different food matrices. Effect-directed detection was performed via A. fischeri and B. subtilis bioassays, tyrosinase and AChE inhibition assays and DPPH* radical scavenging assay. Active unknown zones were further characterized by HPTLC-ESI-HRMS and assigned as [8]-gingerol and [10]-gingerol. Among others, further multi-detected zones were assigned to be [4]-gingerol, dehydro-[6]-gingerdione, dehydro-[6]-gingerol, dehydro-[8]-gingerol, dehydro-[10]-gingerol etc.

J. Planar Chromatogr. 31, 72-78 (2018). HPTLC of equol in ethanolic cattle manure extract on RP-18 with n-hexane – ethyl – acetate – acetone 9:3:2. Detection by planar yeast estrogen screening (pYES) by dipping into a yeast suspension, followed by incubation at 30 °C for 4 h. After incubation, the plate was dried in a 37 °C incubator for 15 min and dipped into the combined reaction buffer followed by incubation at 37 °C for 60 min and 90 % relative humidity. The combined reaction buffer was prepared by mixing 20 mL of buffer C (5.3 g of sodium phosphate dibasic and 0.4 g of potassium chloride were dissolved in about 490 mL water, the solution was adjusted with sodium hydroxide to pH 13, 0.5 g of benzalkonium chloride were added and the mixture was filled up to 500 mL) and 0.2 mL of a freshly prepared X-Gal solution (0.05 g/mL X-Gal in DMSO). Fluorescence evaluation under UV 366 nm. The hRF value for equol was 47.

J. Planar Chromatogr. 31, 213-219 (2018). HPTLC of β-sitosterol in the leaves of five Ficus species (F. carica, F. nitida, F. ingens, F. palmata, and F. vasta) on silica gel with ethyl – acetate 4:1. Detection by spraying with p-anisaldehyde reagent followed by drying. Quantitative determination by absorbance measurement at 550 nm. The hRf value for β-sitosterol was 17. Linearity was in the range of 100-1400 ng/zone. The intermediate precision was below 2 % (n=6). The LOD and LOQ were 32 and 98 ng/zone, respectively. Recovery was between 98.5 and 99.7 %.

Biochem. Biophys. Res. Commun. 491, 265-270 (2018). HPTLC of nitrobenzoxadiazole (NBD)-labeled lipids in the reaction mixture of ceramide glucosyltransferase (GlcT-1) on silica gel with chloroform – methanol – water 65:25:4. NBD-labeled lipids were visualized by UV-B illumination. The amount of C6-NBD-glucosylceramide (GlcCer) generated was quantified by TLC image processing. The method was used to study the effects of JAK/STAT3 pathway inhibitors on GlcT-1 activity.

CBS 120, 14-15 (2018). The drugs cefixime trihydrate (CEFI) and azithromycin dihydrate (AZI) were subjected to hydrolytic degradation (with water, 0.5 N HCl or 0.5 N NaOH), oxidative degradation (with 3 % and 30 % hydrogen peroxide), thermal degradation (heated at 100 °C and 200 °C for 1 h and 2 h) and photolytic degradation (exposed to fluorescent cold white light and UV light). HPTLC of CEFI, AZI, and the degradation samples on silica gel with ethyl acetate – methanol – acetone –_x000D_ toluene – ammonia 2:10:14:1:1 to the migration distance of 80 mm. Detection of AZI by immersion into sulfuric acid reagent (1:4 in ethanol) and heating at 100 °C for 5 min. Evaluation under UV 254 nm, UV 366 nm, and white light. Quantitative determination by absorbance measurement at 235 nm for CEFI and 530 nm for AZI. Linearity was in the range of 500–2500 ng/zone for CEFI and 50–250 ng/zone for AZI. The LOD and LOQ (ng/zone) for CEFI were 58 and 175, respectively, and for AZI 3 and 10, respectively. Precision (%RSD) was <2 %. In the forced degradation studies, CEFI degraded to 4 major products under different stress conditions. AZI showed only one additional peak upon acid and neutral hydrolysis.

J. Chromatogr. A, 1572, 145-151 (2018). Introduction of on-surface reactions as a new strategy for rapid structure elucidation. This was illustrated by a miniaturized on-surface synthesis-guided identification of two new degradation products (impurities) occurring in a pharmaceutical formulation of the anti-cancer drug ifosfamide, especially in the presence of urea. The respective reagents were applied in the nanomole scale accurately and automated on a HPTLC silica gel plate. After a fast reaction in the start zone, the plate was developed, followed by online elution to high-resolution MS, whereby the on-surface reaction highlighted the impurities. As proof of concept and for benchmarking, it was compared to a reaction mixture obtained from conventional preparative synthesis in a round-bottom flask as well as to different formulations. Image evaluation was performed by videodensitometry. Discussion of the advantages such as: 1) the combination of all relevant steps on one HPTLC plate and its resulting efficiency made surface synthesis on chromatographic phases an optimal tool for signal highlighting in MS, and thus for the assignment of impurities in drugs; 2) the miniaturization of the chemistry process scale down to the μg-level per synthesis (in total 30-60 μg chemicals/reaction), setting a new state-of-the-art standard; 3) the contribution to a greener chemistry by reducing the consumption of chemicals and enhancing the analytical efficiency, when adapted for the quality control of any other chemical product.

Pharmacogn. Mag. 14, 45-51 (2018). HPTLC of stigmasterol in Monochoria vaginalis and Monochoria hastata on silica gel with chloroform – methanol 4:1. Detection by spraying with anisaldehyde-sulfuric acid reagent, followed by heating at 105 °C for 5 min. Quantitative determination by absorbance measurement at 540 nm. The hRF value for stigmasterol was 30. Linearity was between 1000 and 5000 ng/zone. LOD and LOQ were 80 and 200 ng/zone. The intermediate precision was <3 % (n=3). Average recovery was 99.8 %.