Analysis of phenolic compounds in black walnut (Juglans nigra L.) fruit extract using high-performance liquid chromatography

Abstract

Black walnut (Juglans nigra L.), which belongs to the Nut family (Juglandaceae), is a valuable raw material for the production of phytopreparations. The extract from the fruits of Juglans nigra L. has immunomodulating and antioxidant properties, which is primarily due to the presence of a large amount of phenolic compounds in the plant. But the phytochemical composition and pharmacological properties of Juglans nigra L. have not been sufficiently studied.
 The aim of our work was to study the optimal conditions for the extraction of Juglans nigra L. fruits, followed by the identification of its quantitative and qualitative composition.
 The main criterion for evaluating optimal extraction conditions was the quantitative content of phenolic compounds, which was determined spectrophotometrically by the Folin–Chocalteu method. The analysis of polyphenolic compounds was carried out by the method of high performance liquid chromatography.
 On the basis of experimental studies, the optimal conditions for extracting the fruits of Juglans nigra L. by maceration method conditions were selected. According to the results of the comparative analysis, it is shown that for the maximum extraction of phenolic compounds, it is advisable to use a 70% water-ethanol mixture as an extractant with a raw material to solvent ratio of 1:9. The method of high-performance liquid chromatography showed that the total content of phenolic compounds in the fruits of Juglans nigra L. is 2 327.09 μg/ml. Analysis of the extract of Juglans nigra L. by high-performance liquid chromatography method showed the presence of such phenolic compounds in plant material samples as catechins, catechin-like substances, flavonols (rutin, quercetin, myricetin), flavanones (naringin, naringenin) and phenolic acids. It should be noted, that the presence of such substances as chlorogenic acid, caffeic acid, kaempferol, hesperidin, genistein and daidzein glycosides, luteolin and apigenin glycosides, luteolin and apigenin in the extract of Juglans nigra L. was not detected.
 A high content of compounds of polyphenolic nature in the fruits of Juglans nigra L. was established. Therefore, this medicinal plant material is promising for further research, in particular, for the development of medicines based on the extract with potential anti-inflammatory, analgesic and antioxidant activity.