J. Planar Chromatogr. 34, 55-60 (2021). TLC of genistein‑7‑O‑[α‑rhamnopyranosyl‑(1 → 6)]‑β‑glucopyranoside (GTG) in Derris scandens on silica gel with ethyl acetate - methanol - water 80:13:10. Quantitative determination by absorbance measurement at 254 nm for (1), 256 nm for (2), 300 nm for (3) and 296 nm for (4). The hRF value for GTG was 26. Linearity was between 8 and 120 µg/mL. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 3 and 9 µg/mL. Recovery was between 102.3 and 108.6 %. The results obtained from the TLC–densitometric, TLC–image analysis and HPLC methods were comparable.

J. Planar Chromatogr. 34, 39-44 (2021). HPTLC of salicylic acid (1), kaempferol (2), gallic acid (3), and protocatechuic acid (4) in Cinnamomum verum on silica gel with toluene - ethyl acetate - formic acid 5:4:1. Quantitative determination by absorbance measurement at 302 nm for (1), 256 nm for (2), 300 nm for (3) and 296 nm for (4). The hRF values for (1) to (4) were 54, 66, 31 and 37, respectively. Linearity was between 200 and 700 ng/zone for (1) and 100 and 600 ng/zone for (2) to (4). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 70 and 200 ng/zone for (1), 40 and 100 ng/zone for (2) to (4). Recovery was between 97.8 and 98.9 % for (1), 98.1 and 99.0 % for (2), 97.4 and 99.2 % for (3) and 98.4 and 99.5 % for (4).

J. Planar Chromatogr. 34, 31-38 (2021). HPTLC of reserpine (1), scopoletine (2), piperine (3), bacoside A (4) and lupeol (5) in a polyherbal formulation (containing Rauwolfia serpentina, Nardostachys jatamansi, Convolvulus pluricaulis, Bacopa monnieri, Piper longum) on silica gel with benzene - ethyl acetate - glacial acetic acid - n-butanol 57:30:10:3 for (1), (2) and (3), n-butanol - glacial acetic acid - water 18:3:4 for (4) and benzene - ethyl acetate 9:1 for (5). Detection by spraying with 5 % methanolic sulfuric acid solution, followed by heating at 80 °C for 20 min. Quantitative determination by absorbance measurement at 254 nm for (1) to (3), 598 nm for (4) and 580 nm for (5). The hRF values for (1) to (5) were 17, 53, 73, 34 and 48, respectively. Linearity was between 1 and 2 µg/zone for (1), 2.5 and 4.5 µg/zone for (2), 10 and 50 µg/zone for (3), 12 and 24 µg/zone for (4) and 1 and 5 µg/zone for (5). Intermediate precision was below 2 % (n=6). The LOD and LOQ were 6 and 20 ng/zone for (1), 13 and 38 ng/zone for (2), 11 and 33 ng/zone for (3), 377 and 1143 ng/zone for (4) and 324 and 982 ng/zone for (5), respectively. Average recovery was 98.1 %for (1), 99.9 % for (2), 99.9 for (3), 99.7 % for (4) and 99.5 % for (5).

J. of Chromatogr. Sci. 59 (7), 634-641 (2021). TLC of ledipasvir on silica gel with ethylacetate – hexane – acetonitrile – trimethylamine 12:7:3:1. Detection by exposure to strong UV irradiation to enhance the fluorescence properties of ledipasvir and densitometric scanning at 315 nm⁠. The hRF of ledipasvir was 28 and of sofosbuvir 36. Linearity was in the range of 5-50 ng/band⁠. The method is suitable for the specific determination of ledipasvir in pharmaceutical tablets without interference from sofosbuvir or excipients, thus for the estimation of ledipasvir in fecal specimens with adequate recovery and for testing the content uniformity of ledipasvir in the pharmaceutical tablets.

Sci. World J. 2020, 7367836 (2020). TLC of ethyl acetate fractions of hydro ethanolic extracts obtained from Cassia siamea leaves (Caesalpiniaceae) on silica gel with chloroform – ethanol 17:3, as well as cassiarin A (an isoquinoline alkaloid, hRF 34) as standard. Visualization under UV light. Densitometry scanning at 368 nm for cassiarin A. Linearity was in the range of 400–1400 ng; intra-day precision was below 4 %; LOD and LOQ values were 3 and 8 ng, respectively; recovery rates were 102.8–120.1 %. The cassiarin A concentrations in the samples (given as w/v, the volumes being those of the first undried hydro-ethanolic extracts) varied depending on the origin (ground and climate) of the leaves.

Foods 9(8), 1136 (2020). TLC of methanolic decoctions and ultrasonication extracts from Zingiber officinale (Zingiberaceae) rhizomes, as well as from commercial ginger formulations, on reverse-phase C18-silica gel with ethanol – water 13:7. Densitometry at 200 nm in absorbance and reflectance modes for 6-shogaol (SHO, hRF 36) and 6-gingerol (GIN, hRF 53). Standards of these vanilloid phenolics were also used for calibration; linearity was in the range of 100–700 ng for SHO and of 50–600 ng/band for GIN; interday and intra-day precisions were below 1.6 %. The LOD and LOQ was 34 and 101 ng for SHO, 17 and 51 ng for GIN, respectively. Recovery rates were 98.8–101.6 % for SHO and 99.0–101.5 % for GIN. For each extract, SHO and GIN levels were calculated, the yields after ultrasonication extraction were 10-25 % higher than with the corresponding decoctions. Comparison with other published methods (LC-MS and HPLC) showed superiority of this new method in terms of linearity range, accuracy and precision.

3 Biotech 10(8), 344 (2020). Rauvolfia serpentina (Apocynaceae) was cultivated in vitro as leaf-derived callus and as plantlet cultures obtained from tissues of nodal explants, without or with cadmium chloride as elicitor of alkaloid production. TLC of methanol – ammonia 10:1 extracts of callus and plantlet organs (leaves, stems and roots) on silica gel, along with indole alkaloids reserpine and ajmalicine in different concentrations. Development with chloroform – toluene – ethyl acetate – diethyl amine 7:7:4:1. Detection under UV light and by densitometry scanning in absorbance mode at 240 nm and 280 nm. The highest alkaloid yields were obtained for reserpine (hRF 15) in roots (191µg/g) and for ajmalicine (hRF 45) in callus (131µg/ml) when culture had been done with elicitor 0.15 mM for 6 days and 4 days, respectively (at 0.20 mM, an inhibiting effect was observed).

J Pharm Bioallied Sci. 12(2), 139-145 (2020). An HPTLC method was validated for the fingerprint of flavonoids and other phenolic compounds (rutin, apigenin, luteolin, caffeic acid, chlorogenic acid, rosmarinic acid) in methanol macerates of dried aerial parts of five Lamiaceae (subfamily Nepetoideae: Dracocephalum moldavica, Lophanthus anisatus, Monarda fistulosa, Ocimum americanum, Satureja hortensis). HPTLC of extracts and standards on silica gel with chloroform – ethyl acetate – formic acid 5:4:1 or with ethyl acetate – formic acid – water 15:1:1. Detection under UV light before and after spraying with aluminium chloride 1 % in methanol. Rosmarinic acid was present and abundant in all extracts and was also quantified by densitometry at UV 366 nm without derivatization. The LOD was 29.2 µg/mL; the rosmarinic acid concentration range was between 12.6 mg/g (Lophanthus) and 24.8 mg/g (Dracocephalum).