J. Chromatogr. Sci. 52 (9), 1089-1094 (2014). HPTLC of the anticancer compound nimbolide in different parts of Azadirachta indica and its dosage form on silica gel with n-hexane – ethyl acetate – acetic acid 30:20:1 (migration distance 68 mm, chamber saturation time 2 min), detection by spraying with 5 % sulfuric acid in methanol, quantification after absorption measurement at 515 nm. Validation by investigation of the (A) hRf value of nimbolide (43), (B) linearity range (200–1400 ng/zone, r2=0.99968), (C) LOD (70 ng/zone) and LOQ (200 ng/zone), (D) recovery (97.5 %, n=3), and (E) specificity (comparison of hRf value and UV/vis absorption spectrum with the standard).

J. Planar Chromatogr. 29, 417-422 (2016). HPTLC of kaempferol (1), quercetin (2), and gallic acid (3) in the herb Euphorbia humifusa on silica gel with chloroform – ethyl acetate – formic acid 26:22:5. Quantitative determination by absorbance measurement at 300 nm for (3) and 400 nm for (1) and (2). The hRF values for (1) to (3) were 18, 36 and 48, respectively. Linearities ranged 168-448 ng/zone for (1), 183-488 ng/zone for (2) and 179-476 ng/zone for (3). The intermediate precision was below 3.3 % (n=6). The LODs and LOQs were 16 and 53 ng/zone for (1), 7 and 23 ng/zone for (2) and 8-23 ng/zone for (3), respectively. Average recoveries were 96.1 % for (1), 98.3 % for (2) and 96.6 % for (3).

Planta Medica 82 (16), 1395-1402 (2016). The hexane – ethyl acetate subfraction of the ethyl acetate fraction of an ethanolic Tabebuia roseoalba leaf percolation extract was subfractioned on a silica gel column with 42500 mL of a gradient of hexane, ethyl acetate, and methanol. For monitoring, TLC on silica gel with hexane – ethyl acetate 1:1, detection with anisaldehyde sulfuric acid reagent. Two fractions that gave only one visible zone on TLC, were identified by NMR as mixtures of stigmasterol and sitosterol, and of alpha- and beta-amyrins, respectively.

Planta Medica 83(03/04), 300-305 (2017). Preparative TLC on 1) RP-18 phase with methanol – water, in several proportions from 2:1 to 9:11 and on 2) silica gel with dichloromethane – ethyl acetate, from 5:1 to 10:3 was applied to purify eight phenylethylchromones from subfractions of a methanolic extract of Aquilaria filaria agarwood. Preparative TLC on silica gel with n-hexane – ethyl acetate 2:1 was also used to separate the products of one of these chromones (2-(2-hydroxy-2-phenylethyl)-4H-chromen-4-one) with the (S)- and (R)-MTPA-Cl (α-methoxy-α-trifluoromethyl-phenylacetyl-chloride) needed for the Mosher ester method for asymmetric carbon configuration, allowing, after NMR, the determination of the chromone as an uneven mixture of R- and S-enantiomers (4:1). The enantiomer separation was done after derivatisation into diastereoisomers (no chiral separation).

J. Planar Chromatogr. 30, 181-187 (2017). HPTLC of guggulsterones E (1) and Z (2) in a polyherbal formulation containing Commiphora Muku on silica gel with toluene – ethyl acetate 4:1. Quantitative determination by absorbance measurement at 251 nm. The hRF values for (1) and (2) were 34 and 41. Linearity was between 0.2 and 1.2 μg/zone. LOD and LOQ were 43 and 132 ng/zone for (1) and 39 and 120 ng/zone for (2), respectively. The intermediate precision was below 2 % (n=3). Average recovery was 94.4 % for (1) and 97.7 % for (2).

Food Chem. 239, 831-839 (2018). HPTLC of saffron on silica gel with 1-butanol – acetic acid – water 4:1:1. Qualitative identification at UV 254 nm. The hRf values of the nine detected zones (crocins and picrocrocin derivatives) were 19, 29, 43, 56, 63, 67, 80, 85, and 96. Captured images were imported to the MATLAB program for pattern recognition and discrimination between different saffron samples on the basis of their soil electro-conductivity values as indicator of soil salinity. The data pre-processing included elimination of chromatographic artifacts such as baseline drifts and spot misalignment.

Food Chem. 239, 1182-1191 (2018). HPTLC of coumarin in 43 commercially available cinnamons and cinnamon containing foods on silica gel with n-hexane – ethyl acetate – ammonia 76:26:1. Detection by dipping into a 10 % ethanolic potassium hydroxide solution, followed by drying, and dipping into a 10 % methanolic PEG 400 solution for stabilization of the fluorescence. Quantitative determination by fluorescence measurement at 366/>400 nm. The contents ranged from 0.3 to 5129 mg/kg with mean intermediate precisions of 4 %. The hRF value for coumarin was 50. LOD and LOQ were 200 and 400 pg/zone, respectively. Confirmation of preliminarily assigned coumarin zones was performed with a single quadrupol MS and HRMS. Effect-directed detection was also performed and coumarin was active against A. fischeri bacteria down to 100 ng/band.

Hoffm. A review. J. Ethnopharmacol. 220, 294-320 (2018). Review of the phyto-constituents of Arctotis arctotoides, including the application of TLC and HPTLC for the analysis of steroids and acids, alcohol and phenolics, guaianolides, germacranolide, eudesmanolides, farnesol derivatives and sesquiterpenes. The review also described bio-autographic methods on TLC plates against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Shigella sonnei) bacteria.