Flavonol reagent

The dark zone (>) directly above rutarin derives from the flavonol glycoside lutin, which develops a bright orange fluorescence in UV-355 nm when treated with the Natural product/PEG reagent (Appendix A, No. 28 Rutin see 7.1.7, Fig. 4). 

Samples (3 pi) of flavones and flavonols are applied to a silica plate and developed to 8.5 cm (35 min) with ethyl acetate-formic acid-acetic acid-water (100 11 11 27) as the mobile phase. After development, the plate is dried and inspected under longwave UV before and after it has been sprayed with the NP/PEG 4000 reagent. Typical Ry values and colors for some flavonoids are given in Table 3. 

Flavonoids are known to occur widely in woody plants and are found in both hardwoods and softwoods (18). Generally, their presence is not obvious until the alcohol-soluble extractives are studied in detail. Some wood flavonoids such as the flavonol fisetin are intensely fluorescent in ultraviolet light and are thus readily detected, even when present in trace amounts. Other common wood flavonoids such as dihydroquercetin are dull absorbing in ultraviolet light and can only be detected satisfactorily by use of chromogenic reagents. 

Quercetin, a natural flavonol, oxidized with iV-bromosuccinimide, has been demonstrated as a colored extraction reagent for the determination of cetylpyridinium chloride and other amines (143). 

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