Planta Med. 84(12-13), 935-940 (2018). Atropine sulfate was hydrolyzed into tropine in a bath of barium hydroxide 8% (temperature 75°C, time 16h). For verification, an aliquot of the final solution was extracted into dichloromethane, which was applied, as well as alkaloid standards, on TLC silica gel and eluted with dichloromethane – ethanol – triethylamine 46:46:1. The reaction was confirmed as complete.

J. Planar Chromatogr. 33, 281-291 (2020). HPTLC of piperine in the fruit of Piper nigrum on silica gel with toluene - ethyl acetate - formic acid - methanol 15:15:4:1. Detection by dipping into anisaldehyde sulfuric acid reagent, followed by heating at 105 ºC for 5 min. Quantitative determination by absorbance measurement at 366 nm. The hRF value for piperine was 71. Linearity was between 100 and 500 ng. Intermediate precision was below 4 % (n=5). The LOD and LOQ were 72 and 218 ng, respectively. Average recovery was 98.8 %.

J. Planar Chromatogr. 33, 313-319 (2020). HPTLC of berberine (1) and rutin (2) on silica gel with n-hexane - ethyl acetate - glacial acetic acid - methanol 100:11:11:25. Quantitative determination by absorbance measurement at 241 nm. Antioxidant activity was determined by dipping into a 0.05 % DPPH solution followed by qualitative analysis at 366 nm. The hRF values for (1) and (2) were 67 and 47, respectively. Linearity was between 0.2 and 1.4 µg/zone for (1) and 2 and 14 µg/zone for (2). Intermediate precision was below 1 % (n=6). The LOD and LOQ were 0.2 and 2 µg for both (1) and (2), respectively. Average recovery was 94.9 % for (1) and 96.3 % for (2).

Pharmacogn. Mag. 15, 256-260 (2019). HPTLC of piperine (1), asiaticoside (2), and withanolide A (3) in a polyherbal formulation of Piper longum, Centella asiatica, and Withania somnifera on silica gel with toluene - ethyl acetate 9:1 for (1), ethyl acetate - methanol - water 20:5:2 for (2) and toluene - ethyl acetate - formic acid 5:5:1 for (3). Detection by spraying with 5 % aqueous sulfuric acid, followed by heating at 110 °C. The developed plates were scanned at 254 nm, 366 nm and visible light. The hR_F values for (1) to (3) were 24, 71 and 77, respectively.

J. Liq. Chromatogr. Relat. Technol. 43, 351-360 (2020). HPTLC of colchicine (1) and gloriosine (2) in Gloriosa superba on silica gel with chloroform - acetone - di-ethylamine 5:4:1. Quantitative determination by absorbance measurement at 350 nm. The hR_F values for (1) and (2) were 50 and 40, respectively.  The study promotes the use of G. superba as an adjuvant therapy in gouty arthritis and helps explore the elite chemotype(s) with validated pharmacological action to meet out the medicinal and commercial demands.

J. Liq. Chromatogr. Relat. Technol. 43, 388-393 (2020). HPTLC of carpaine in the leaves of Carica papaya on silica gel with chloroform - methanol 7:3. Detection by dipping into Dragendorff’s reagent. Quantitative determination by absorbance measurement at 510 nm. The hR_F value for carpaine was 59. Linearity was between 0.4 and 1.2 µg/zone. Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 11 and 33 ng, respectively. Recovery was 101.6 %.

J. Planar Chromatogr. 33, 43-50 (2020). HPTLC of trigonelline in coffee samples with ethyl acetate - methanol - water - formic acid 54:23:15:8. Quantitative determination by absorbance measurement at 267 nm. The hR_F value for trigonelline was 24. Linearity was between 100 and 700 ng/zone. Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 33 and 110 ng/zone. Recovery rate was between 97.6 and 99.4 %.

J. Planar Chromatogr. 33, 33-41 (2020). HPTLC fingerprint of the kernel and seed of Allanblackia parviflora fruit (extracted with methanol - water 4:1) on silica gel with methanol - water - ethyl acetate 33:27:200. Detection by spraying with vanillic acid - sulfuric acid reagent (1 g of vanillic acid in 100 mL of 96 % ethanol, followed by the dropwise addition of 2 mL concentrated sulfuric acid). Different formulations of the derivatization reagent were investigated and the use of vanillic acid instead of the more frequently used vanillin provided a better result. Qualitative determination under UV 254 and 366 nm. Consistent hR_F values of the main zones under UV 254 nm were 39, 35 and 12. For the derivatized plate, consistent hR_F values of the main zones were 39, 34, 31 and 22.