J. Planar Chromatogr. 34, 229-242 (2021). HPTLC of chlorthalidone (1) and metoprolol succinate (2) on silica gel with toluene - methanol - triethylamine 16:4:1. Quantitative determination by absorbance measurement at 230 nm. The hRF values for (1) and (2) were 44 and 23. Linearity was between 200 and 1000 ng/zone for (1) and 800 and 4000 ng/zone for (2). Intermediate precisions were below 2 %. The LOD and LOQ were 29 and 88 ng/zone for (1) and 151 and 459 ng/zone for (2), respectively. Recovery was between 99.9 and 100.9 % for (1) and 100.4 and 101.6 % for (2).

J. Planar Chromatogr. 34, 279-283 (2021). HPTLC of linagliptin on silica gel with toluene - methanol 7:3. Quantitative determination by absorbance measurement at 294 nm. The hRF value for linagliptin was 91. Linearity was between 100 and 500 ng/zone. Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 0.26 and 0.78 ng/zone, respectively. Recovery was between 99.1 % and 101.2 %.

J. Food Sci. 85, 3183-3190 (2020). HPTLC of astragalosides standards (I-IV) in Pleurotus ostreatus on silica gel with trichloromethane - methanol - ethyl acetate - water 13:7:2:2. Detection by spraying with 10 % sulfuric acid in ethanol and visualization under IV light at 365 nm. The hRF values for (I) to (IV) were 71, 54, 34 and 31, respectively. Further analysis by mass spectrometry.

J. Ethnopharmacol. 270, 113842 (2021). HPTLC of diosgenin in the rhizomes of Paris polyphylla on silica gel with toluene - ethyl acetate 7:3. Detection by spraying with anisaldehyde sulphuric acid reagent, followed by heating at 105 °C for 5 min. Quantitative determination by absorbance measurement at 430 nm. The hRF value of diosgenin was 53.

Phytochem. Anal. 3093 (2021). HPTLC of hyperforin (1), hypericin (2) and hyperoside (3) in Hypericum species on silica gel with n-hexane - ethyl acetate 4:1 for (1), toluene - chloroform - ethyl acetate - formic acid 80:50:35:6 for (2) and ethyl acetate - formic acid - acetic acid - water 15:2:2:1 for (3). Detection by spraying with a derivatizing reagent (20 mL of sulfuric acid were carefully added to 120 mL methanol and diluted with 200 mL methanol), followed by heating. Quantitative determination by absorbance measurement at 366 nm. The hRF values of (1) to (3) were 49, 35 ad 49, respectively. Linearity was between 0.4 and 1.4 µg/zone for (1), 20 and 100 ng/zone for (2) and 10 and 100 ng /zone for (3). The intermediate precision was below 2 % (n=6) for (1) to (3). The LOD and LOQ were 120 and 400 ng/zone for (1), 6 and 20 ng/zone for (2) and 3 and 10 ng/zone for (3), respectively. Recovery was between 101.0 and 101.2 % for (1), 98.8 and 100.1 % for (2) and 100.4 and 101.4 % for (3).

Phytochem. Anal. 3078 (2021). HPTLC of thymoquinone on silica gel with cyclohexane - ethyl acetate 9:1 (1) and on RP with ethanol - water 4:1 (2). Quantitative determination by absorbance measurement at 259 nm. The hRF value of thymoquinone was 42 for system 1 and 51 for system 2. Linearity was between 25 and 1000 ng/zone for (1) and 50 and 600 ng/zone for (2). The intermediate precision was below 1 % (n=6) for (1) and (2). The LOD and LOQ were 8 and 25 ng/zone for (1) and 17 and 50 ng/zone for (2), respectively. Recovery rate was between 99.0 % and 100.9 % for (1) and 98.4 % and 101.2 % for (2). Analytical GREEnness (AGREE) scores for the systems were predicted using the AGREE software according to the 12 principles of green analytical chemistry.

Phytochem. Anal. 33, 83-93 (2022). HPTLC of table olives (Olea europaea) on silica gel with dichloromethane - methanol - acetic acid 45:5:1. Detection by spraying with sulfuric vanillin reagent (5 % vanillin in methanol - 5 % sulfuric acid in methanol 1:1) and under UV light at 254 and 366 nm. Further analysis by nuclear magnetic resonance. 

Phytochem. Anal. 33, 115-126 (2022). HPTLC bioautography of 14 Egyptian plants on silica gel with methylene chloride - methanol 9:1 (system I) or ethyl acetate - methanol - water - glacial acetic acid 120:20:16:1 (system II). Detection by spraying with anisaldehyde/sulfuric acid reagent. Aromatase inhibitory assay was performed by dipping into 112.5 mL cofactor solution (containing 4.5 mL of 0.5 % sodium phosphate buffer, 4.5 mL NADPH regenerating system solution A and 0.9 mL NADPH regenerating system solution B and then completed to volume with distilled water), followed by incubation at 37 °C for half an hour, then re-immersed in 75 mL aromatase E/S mix (containing 120 μL aromatase enzyme, 0.03 mL DBF and 3 mL albumin dissolved in 0.075 M potassium phosphate buffer) and re-incubated for another half an hour. Enzymatic reaction was terminated by immersing plates into 2N sodium hydroxide stop solution. Active zones were observed under UV 366 nm. Calculation of the inhibition zones was performed by reciprocal iso-inhibition volume (RIV) that is based on measuring the zone pixel intensity. The hRF values for chrysin were 63 and 91 in systems I and II, respectivley. The intermediate precision was below 3 % (n=3). Linearity was between 0.1 and 0.3 μg/zone. LOD and LOQ were 80 and 206 ng/zone, respectively. Recovery was between 92.5 and 106.5 %. Two quantification methods, the peak area and RIV method were compared and the RIV method showed superiority over the peak area method with %RSD values of 0.98 and 1.49 compared with 2.86 and 3.58, respectively.