Development of approaches to standardization of black walnut bark

Abstract

Significance. Black Walnut (Juglans nigra L.) is a species of trees of the Walnut family (Juglandaceae). This plant of the genus Walnut (Juglans L.) has not been sufficiently studied unlike other species e.g. Juglans regia L. This medicinal plant raw material is quite perspective, its preparations have antimicrobial, general tonic effect. We can use its leaves, unripe fruit, and the bark. However they are not widely used in medicine. In order to introduce the plants of the Walnut genus to the State Pharmacopoeia of the Russian Federation (RF State Pharmacopoeia), it is necessary to conduct of pharmacognostic studies, to develop product specification file to confirm the identification and quality of medicinal plant raw materials. The aim of this study is to develop a method of quantitative determination of flavonoids in the bark of the black walnut (Juglans nigra L.). Materials and methods. Material of the study was black walnut bark, stocked during the sap flow period (April) in 2018. The bark was skived up to 15 cm long and 23 cm wide. The bark was air-dried with the protection from direct sun light. The end of the drying was checked by the brittleness of the bark. Results. The methods of the quantitative determination of flavonoids in walnut bark has been developed. We used the differential spectrophotometry taking into consideration state standard sample of rutin at the analytical wavelength of 416 nm. The error of a single determination with a confidence level of 95% is 1.20%. Conclusion. We used the developed technique and analyzed a number of samples of black walnut bark. The content of total flavonoids in the plant raw material is 5.13 0.02% (as calculated on rutin). The flavonoid content should be at least 4.0%.