Planta Med. 85(2), 112-117 (2019). A fraction of an ethanolic extract of Dolichos trilobus roots (Fabaceae) was eluted on a silica gel column with different mixtures of petroleum ether and acetone. This fractionation was monitored by TLC on silica gel (eluent not given), derivatization by spraying with sulfuric acid 10 % (in ethanol) and heating (100 °C). Further isolation steps allowed the identification of eight coumestans in two subfractions: dolichosins A–D, isosojagol, phaseol, psoralidin, dehydroisopsoralidin.

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).

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).

J Am Soc Mass Spectrom 31(9), 1981-1993 (2020). Low-temperature plasma-mass spectrometry was studied for comparison between direct desorption (DD) and diode laser assisted desorption (LD) in terms of quantitative and qualitative analysis of compounds from cellulose vs. silica gel TLC layers. Compounds (the 20 common amino acids, propofol, nicotine, cotinine, salicylamide, acetylsalicylic acid, paracetamol, caffeine, valprolactone and its isomer 4-ene-valproic acid) were applied on the TLC plates (without development) at different concentrations; a commercial mixture of acetylsalicylic acid, paracetamol and caffeine was also applied on TLC plates, developed with dichloromethane – ethyl acetate 1:50, detection at UV 254 nm and quantitative MS. In general, DD provided good results on cellulose, where LODs where between 0.01 and 2.55 ng/mm2, whereas several compounds remained undetected on silica gel. LD however provided LODs on silica gel from 0.3 to 84 pg/mm2. Tandem MS with collision-induced dissociation was implemented to improve signals, LODs and to characterize the other analytical figures-of-merits (including detection of the main fragment ions, determination of optimal laser beam width and irradiance depending on the compounds). For the two metabolites of valproic acid, the ions and fragments had identical values; therefore, a mix of the two isomers had to be applied and separated with dichloromethane – methanol 50:1 before MS; one half of the plate was visualized for control by dipping into potassium permanganate reagent (7.5g KMnO4, 50g K2CO3, 0.75g NaOH in 1L water).

J. Planar Chromatogr. 33, 567-577 (2020). HPTLC of atropine (1), caffeic acid (2) and chlorogenic acid (3) in the root, stem and leaf samples of different populations in two cytotypes of Physochlaina praealta on silica gel with methanol - acetone - diethylamine 25:24:1 for (1) and toluene - ethyl acetate - methanol - formic acid 75:25:10:6 for (2) and (3). Detection by spraying with Dragendorff’s reagent for (1) and anisaldehyde for (2) and (3). Quantitative determination by absorbance measurement at 254 and 500 nm. The hRF values for (1) to (3) were 18, 72 and 77. Linearity was between 2 and 12 µg/zone for (1) to (3). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 490 and 1490 ng/zone for (1), 170 and 530 ng/zone for (2) and 220 and 650 ng/zone for (3), respectively.

Planta Med. 84(18), 1348-1354 (2018). A subfraction (obtained through liquid-liquid partition and column chromatography) of the ethanolic extract of whole Vernonia cinerea plants (Asteraceae, subf. Cichorioideae) was further fractioned by reverse-phase SPE (solid-phase extraction) followed by preparative TLC on silica gel layer (eluent not given). For verification, zones were detected by spraying with anisaldehyde solution with 10 % sulfuric acid, followed by heating at 100 °C. Further purification by reverse-phase HPLC allowed the isolation of 6 hirsutinolide-type sesquiterpenoids (all with a oxacyclonane forming an ether bridge), including vernolides A and B.

Planta Med. 84(18), 1340-1347 (2018). Preparative TLC on silica gel for the final purification of 15 phenylethyl-chromenone derivatives (including 3 with epoxide functions), 4 sesquiterpenoids (neopetasane, dehydrokaranone, dioxoselinene, ligudicin C) and a steroid (ergostatetraenone), all isolated through multi-step column chromatography from the ethyl-acetate fraction of a methanolic extract of Aquilaria sinensis resinous wood (Thymelaeaceae). For each compound, mobile phase, RF value and yield are given.

Phytochem. Anal. 31, 801-808 (2020). HPTLC of agarwood on silica gel with chloroform - methanol - distilled water 10:7:5. Detection by absorbance measurement at 254 nm. Agarotetrol was used as reference substance. Qualitative results were in agreement with the liquid extraction surface analysis mass spectrometry method.