Optimization of temperature affected extraction of indigo dye in the leaf extracts of Polygonum tinctorium Ait. cultivated in Poland--preliminary studies.

Polygonum tinctorium Ait. (Polygonaceae) known as dyerís knotweed is an annual plant growing in the sandy and loamy soils of China, Japan and Eastern Russia, where it is cultivated for both industrial and pharmacological usage (1). Indigo one of its main constituents has been widely used in traditional chinese medicine, and also, as a natural dye, in the production of denim. Although its synthesis is already known, significant amounts of indigo are still being recovered from naturally occurring plant material for medicinal use, by means of water extraction and alkaline precipitation (2). Currently, indigo-related compounds are of significant interest both as natural colorants and pharmacologically active compounds. Numerous references treating on their detoxifying, antipyretic, antiviral, antidermatophytic or antinociceptive properties confirm the importance of their recovery (35). The aim of presented study was to analyze the indigo dye content in the leaf extracts of Polygonum tinctorium Ait. collected in the late summertime (beginning of September) and late fall (mid October after ground-frost) from the garden of Chair and Department of Pharmacognosy (Medical University of Lublin) located in Poland, to check, whether the production of indigo by plant cells differs depending on the climatic conditions. Up to date, dyerís knotweed has been cultivated for medicinal use mainly in Asia. Satisfactory content of indigo in P. tinctorium cultivated in Poland from seedlings could be meaningful and spread the cultivation area of this plant to cooler climatic zones. Seasonal variations in the production of indigo in the Polish specimen were monitored and compared to its content in dried leaf of dyerís knotweed of Chinese origin. Furthermore, the influence of different extraction pattern on indigo content in the leaf extracts was measured.