Application of TLC for the assessment of the flavonoid profile of sea buckthorn leaves during different phases of their preparation
Authors: Trineeva Olga V. , Kovaleva Natalya A. , Safonova Elena F. , Slivkin Alexey I. 
Published: August 2024

Sea buckthorn (Hippophae rhamnoides L.) is a perennial wind-pollinated dioecious berry shrub. The leaves, according to the literature, contain flavonoids, tannins, vitamins, organic, polyunsaturated fatty acids and amino acids and are a source of phenolic compounds (flavonoids, tannins, phenolic acids). According to the literature, sea buckthorn leaves contain various flavonoids, extracted mainly by alcohol-water mixtures. Thus, the composition of the flavonoid complex contains derivatives of quercetin, isorhamnetin and kaempferol (rutin, quercitrin, myricetin, luteolin, vitexin, narcissin, etc.). According to the authors, the annual supply of sea buckthorn leaves in the Greater Caucasus is 3-5 tons. Moreover, the leaves are an annually renewable by-product obtained during the procurement of the main raw material – fruits, which determines the relevance of comprehensive studies of the phytochemical composition of leaves within the framework of resource-saving technologies for the production of herbal medicines.
The purpose of our study was to substantiate the choice of conditions for the chromatographic separation of flavonoids from sea buckthorn leaves using TLC and investigation of their composition at different harvesting times.
Based on the parameters of chromatography efficiency, using a set of methods for visual assessment of chromatograms and their processing using the computer program “Densitometer Sorbfil”, the optimal conditions were selected for the separation of flavonoids from sea buckthorn leaves in a thin layer of sorbent: mobile phase ethyl acetate-glacial acetic acid-water (5:1: 1); developer – 5% alcohol solution of aluminium chloride when observed under UV light; 7 µl of extraction using HPTLC plates “Silica gel 60 F254” (10x15 cm). The presence of 18 biologically active substances with a flavonoid nature has been established. It has been established that when leaves are harvested from the beginning of June to the end of August (phases 1-3), the qualitative composition of pigments does not change. However, when the leaves are collected simultaneously with the fruits, in the TLC profile of the extracts, the zones of flavonoids were visually characterized by a smaller area and colour intensity than when they were harvested during the period of fruit formation. Now, research to substantiate the optimal phase of harvesting leaves from the point of view of their phytochemical composition and preserving the value of the fruit is ongoing. However, the method developed in the study can be recommended for inclusion in modern ND for sea buckthorn leaves of any phenological phase of plant life for the identification of a specific flavonoid profile of this raw material. In further studies, it is also necessary to evaluate the influence of the climatic conditions of plant growth, cultivation characteristics and varietal diversity on the reproducibility of the TLC profile of leaf flavonoids obtained in this study.