Reagent vanillin-phosphoric acid

Classical examples of this type of reaction are the various dimethylaminobenz-aldehyde reagents (q.v.) and vanillin-acid reagents, of which one, the vanillin-phosphoric acid reagent, is already included in Volume 1 a. The aldol condensation of estrogens is an example for the reaction mechanism (cf. Chapter 2, Table 6). According to Maiowan indole derivatives react in a similar manner [1]. Longo has postulated that catechins yield intensely colored triphenylmethane dyes [2]. 

Test for phytosterols after derivatization with vanillin-phosphoric acid reagent (shots taken in white light) ... 

A Natural products-polyethylene glycol reagent (NP/REG No. 28) —> UV-355nni B Vanillin-phosphoric acid (VP reagent No. 41) —> vis... 

B Vanillin-phosphoric acid reagent (VPA No. 41) —i vis C Antimony-(III)-chloride reagent (SbCljNo. 4) —> UV-365 nm... 

Thin-layer chromatography (TLC) is a good method for detecting the presence of cucurbitacins in a plant extract. The best results to date have been achieved using high-performance TLC (HPTLC) plates [41] with silica gel and chloroform-methanol (95 10) (Table 1) or toluene-ethyl acetate (25 75) as mobile phases [3,11]. Reversed-phase (RP) HPTLC plates with methanol-water (7 3) have also been used to separate cucurbitacins [3]. The compounds are easily detected with vanillin-sulphuric acid or vanillin-phosphoric acid reagents and ultraviolet light (UV) at 365 nm [11]. 

Fig. 3a The TLC of the ethanol extracts of Radix Trichosanthis sprayed with Vanillin-Phosphoric acid reagent (VIS)...

Some of the innumerable reagents used in TEC are based on reactions with more or less well-established mechanism. Eor example, sodium iodobismuthate (Dragendorff reagent) is widely used among others for alkaloids and quaternary ammonium compounds, 4-dimethylaminobenzaldehyde for primary amines and amino acids, 2,4-dinitrophenylhydrazine for aldehydes and ketones, ninhydrin for amino acids and some antibiotics, fluorescamine for primary and secondary amines, phosphomolybdic acid for lipids, various steroids, and other compounds, chlorine vapor followed by Kl/starch for amines and amides. More complex is the mechanism of the reactions with some other reagents, containing high concentrations of sulfuric acid, vanillin/sulfuric acid, phosphoric acid, aluminum chloride, antimony(III)... 

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