Objective: Considering the growing interest of researchers in a wide range of pharmacological effects characteristic of quince raw materials due to the presence of various groups of biologically active substances (BAS). The object of the study was fruits Cydonia oblonga Mill obtained in the Botanical Garden of Sechenov University, the Botanical Garden of Moscow State University, the Moscow and Krasnodar regions, harvested during the fruiting phase. Materials and methods: The analysis was performed on a GILSON high-performance liquid chromatograph, model 305 (France). Detection was carried out using a GILSON UV/VIS model 151 UV detector at a wavelength of 370 nm. The total content of polyphenols in the studied raw materials was estimated by Folin-Chicalteu spectrophotometry, the quantitative content of hydroxycinnamic acids in quince fruits was determined by spectrophotometry in terms of caffeic acid Results and discussions: The authors studied the composition of polyphenolic compounds and carried out their quantitative assessment, using HPLC analysis, the presence of polyphenolic substances represented by caffeic, gallic, chlorogenic, neochlorogenic, cinnamic acids, as well as catechin, quercetin, floretin and apigenin was established. A quantitative assessment of the total content of polyphenolic substances in fruits was carried out using the Folin-Chicalteu method, during which it was revealed that the content of the polyphenolic complex ranges from 8,775 to 9,221 in fresh raw materials and from 6,799 to 7,676 in dried raw materials. Losses of phenolic compounds during drying range from 16.8 to 22.5%. The total content of hydroxycinnamic acids in terms of caffeic acid was carried out by spectrophotometric analysis. The results obtained showed the content of analyzed substances in the determined raw materials from 2,021 to 2,344 in dried raw materials and from 3,126 to 3,526 in fresh. Conclusion: The analysis makes it possible to identify phenolic derivatives in extracts from quince fruits, which simplifies the standardization of raw materials in the preparation of appropriate regulatory documentation. © 2025 Elsevier B.V., All rights reserved.