Vegetational variation of phenolic compounds in Epilobium angustifolium

Epilobium angustifolium L. herbs are used in ethnomedicine to treat benign prostate hyperplasia. The aim of the study was to investigate the phenolic contents in distinct E. angustifolium organs during the whole vegetational period from May to October. The plants were obtained from a remote habitat in Estonia and spectrophotometrically analysed for the total polyphenol, tannin, and flavonoid contents. The total polyphenol content was the highest in roots (85 mg g(-1)) and stems (67 mg g(-1)) in July. The total flavonoid content was the highest in leaves (2.36 mg g(-1)) and flowers (2.09 mg g(-1)) and it remained relatively stable during the summer months. The highest tannin content was found in small growing plants in May; in older ones it declined, whereas the absolute yield per plant was greater. In sum, the aerial organs without stems collected in July-August are the best choice to get E. angustifolium plant material with stable high phenolic content.