Phytochem. Anal. 31, 57-67 (2019). HPTLC of gymnemagenin in the leaves of Gymnema sylvestre on silica gel with toluene - chloroform - methanol 5:8:3. Detection by spraying with vanillin sulphuric acid reagent, followed by heating at 110 ºC for 5 min. Quantitative determination by absorbance measurement at 610 nm. The hR_F value for gymnemagenin was 37. Linearity was between 400 and 3000 ng. The LOD and LOQ were 68 and 206 ng, respectively.

J. Liq. Chromatogr. Relat. Technol. 43, 414-423 (2020). HPTLC fingerprint of Ganoderma lucidum fruiting body on silica gel with toluene - tetrahydrofuran - acetic acid 70:30:1. Detection by dipping into a solution of 10% sulfuric acid in methanol, followed by heating at 100 ºC for 3 min. Qualitative determination under UV light at 254 and 366 nm. The hRF values for ganoderic acids D, B, A, G and C2 were in the zone between 10 and 50. This zone was used for quantification of total triterpene acids by absorbance measurement at 260 nm. Linearity of each of the main peaks between hRF 10 to 50 was determined. The linear range of ganoderic acid A was between 200 and 500 ng/zone.  The study proposes a new method for evaluation, based on “comprehensive high-performance thin layer chromatography (HPTLC) fingerprinting.” Instead of several different methods using different chromatographic techniques, a single HPTLC analysis for identification of Ganoderma lucidum fruiting body with a test for adulteration and quantitative determination of the content of total triterpene acids is proposed. As an alternative to the current tests in the  USP monograph on G. lucidum fruiting body this HPTLC method is a single, low-cost test, which eliminates the UHPLC assay of total triterpene acids.

J. Planar Chromatogr. 32, 339-342 (2019). HPTLC of withaferin A (1) and withanolide A (2) in Solanum nigrum on silica gel with toluene - ethyl acetate - formic acid - ethanol 60:30:1:6. Detection by spraying with p-anisaldehyde sulfuric acid (1 mL of p-anisaldehyde solution in 2 mL of concentrated sulfuric acid and 100 mL of acetic acid). Quantitative determination by absorbance measurement at 530 nm. The hRF values for (1) and (2) were 43 and 55, respectively. 

Planta Medica 84(1), 59-64 (2018). A multi-step fractionation through silica gel column chromatography (CC) of a methanolic extract of Plectranthus africanus (whole plant, Lamiaceae) was monitored through TLC on silica gel with various solvent mixtures (n-hexane or dichloromethane with either acetone or methanol). Zones were detected under UV and further by spraying with sulfuric acid 20 % and heating at 100°C. For each fraction or TLC profile, the authors provide the CC gradient, the optimal proportions of the solvents used for the TLC mobile phase, as well as the RF values of the molecules isolated by this CC method: new abietane-type diterpenoids (plectranthroyleanones A, B, C), betulinic and oleanolic acids, heterosides of apigenin, rhamnetin and sitosterol.

J. AOAC Int. 102, 1014-1020 (2019). HPTLC of asiaticoside in Centella asiatica on silica gel with toluene - ethyl acetate - methanol - glacial acetic acid 2:7:3:1. Detection by spraying with anisaldehyde sulfuric acid reagent. Quantitative determination by absorbance measurement at 595 nm. The hRF values for asiaticoside were between 43 and 47 in the standard, plant powder and marketed formulations. Linearity was between 200 and 1800 ng/zone. Intermediate precisions were below 2 % (n=6). The LOD and LOQ were 51 and 155 ng/zone. Recovery rate was between 97.7 and 105.5 %.

Rev. Bras. Farmacogn. 29, 177-181 (2019). HPTLC of chlorogenic acid (1), 3,4-O-dicaffeoylquinic acid (2), and 3,5-O-dicaffeoylquinic acid (3) in the leaves of Pluchea indica on silica gel with ethyl acetate - water - formic acid - toluene 20:2:2:1. Quantitative determination by absorbance measurement at 326 nm. The hRF values for (1) to (3) were 34, 63 and 79, respectively. Linearity was between 100 and 400 ng/zone for (1) to (3). Intermediate precisions were below 3 % (n=3). The LOD and LOQ were 9.9 and 30.1 ng/zone for (1), 17.6 and 53.3 ng/zone for (2) and 6.7 and 20.2 ng/zone for (3), respectively. Recovery rate was 99.0 % for (1), 97.5 % for (2) and 99.6 % for (3).

J. Planar Chromatogr. 32, 461-465 (2019). HPTLC of betulinic acid (1), oleanolic acid (2) and lupeol (3) on silica gel with benzene - ethyl acetate - formic acid 679:227:94 for (1), n-hexane - ethyl acetate - glacial acetic acid 40:20:1 for (2) and n-hexane - ethyl acetate 4:1 for (3). Detection by spraying with anisaldehyde sulfuric acid, followed by heating at 105-110 ºC for 5-10 min. Quantitative determination by absorbance measurement at 530 nm. The hRF values for (1) to (3) were 79, 46 and 44, respectively. Intermediate precision was below 2 % (n=3).

J. Planar Chromatogr. 32, 379-384 (2019). HPTLC of trigonelline (1) and diosgenin (2) in the seeds of Trigonella foenum-graecum L. on silica gel with acetonitrile - water 3:1. Quantitative determination by absorbance measurement at 267 nm for (1) and at 430 nm after derivatization with vanillin - sulfuric acid for (2). The hRF values for (1) and (2) were 29 and 17, respectively. Linearity was between 200 and 1400 ng/zone for (1) and 50 and 300 ng/zone for (2). Intermediate precision was below 2 % (n=6). The LOD and LOQ were 7 and 1 ng/mL for (1) and 7 and 19 ng/mL for (2), respectively. Recovery rate was between 97.8 and 99.1 % for (1) and 98.2 and 99.3 % for (2), respectively.