Effect of dandelion roots heat pre-treatment on the hydroxycinnamic acids extraction

Introduction. Extraction increasing of biologically active substances (BAS) is one of the important problems of modern pharmacognosy and technology of herbal medicines. This problem is especially relevant for medicinal plant raw materials (MPRS) with a small content of BAS. One solution could be the heat pre-treatment of MPRS. To perform heat pre-treatment, it is advisable to experimentally select parameters that ensure the highest yield of BAS from the processed MPRM.

Aim. To study the influence of thermal pre-treatment parameters of dandelion roots on the content of hydroxycinnamic acids (HCA).

Materials and methods. The object of the study was air-dried dandelion roots from six series. Quantitative determination of the total content of HCA in terms of caffeic acid was determined by spectrophotometry with Arnov's reagent. The qualitative composition of HCA was determined by high-performance liquid chromatography by comparison with standards. Thermal pre-treatment of roots was carried out in an air sterilizer at different temperatures. The content of HCA was compared with the activity of polyphenol oxidase.

Results and discussion. Temperature, duration of thermal pre-treatment, presence of packaging, layer thickness and condition of raw materials by degree of grinding statistically significantly affect the extraction of HCA. Extraction of HCA in comparison with untreated raw materials increases by 36.0 %, qualitative composition and ratio of the main identified HCA (caffeic, chlorogenic, chicory, gallic, p-coumaric acids) do not change when pre-treatment is carried out at a temperature of 140 °С in foil for 1 hour in the thickness of the raw material powder layer with a particle size of 355 µm and less up to 1 cm. During heat pre-treatment, the content of HCA is interconnected with the activity of polyphenol oxidase and the treatment temperature: in the range from 40 to 120 °С a direct dependence was revealed, in the range from 120 to 140 °С it changes to the opposite.

Conclusion. Optimal parameters for heat pre-treatment of dandelion roots have been established, increasing the extraction of HCA without changing their composition and ratio. The identified parameters can be used to obtain extracts from dandelion roots with a high content of HCA for the further development of technologies for obtaining extraction herbal medicines, methods for isolating individual HCA or methods for their quantitative determination.

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