Antioxidant and antimicrobial activity of willow herb (Epilobium angustifolium L.)

Increased free-radical production and inflammation play an important role in development of prostatitis and benign prostatic hyperplasia. One of promising approaches for treatment of those diseases is use of willow herb (Epilobium angustifolioum L., Onagraceae) [1]. The purpose of present research was to evaluate in vitro antimicrobial and antioxidant activity of water and ethanol extracts of leaves and flowers of willow herb. Herbal samples were collected in full blossom from Velebit Mountain, Croatia, and ethanol and water extracts was prepared and freeze-dried. Antimicrobial activity was investigated against ATCC microbial strains, as well as against clinical isolates of Staphylococcus aureus (including MRSA), E. coli ESBL-positive, Proteus mirabilis, Pseudomonas aeruginosa, and Candida albicans using CLSI recommendations. Furthermore, antioxidant activity was determined by β-carotene-linoleic acid and reducing power assay as well as radical scavenging activity of DPPH free radical using colorimetric test and electron paramagnetic resonance (EPR) spectroscopy. Ethanol extracts from leaves and flowers exhibited marked antimicrobial activity with MIC values between 7.13 and 18.25mg/mL against all microbial strains tested. Water extracts were found bactericidal only against MRSA strains with MIC 5.83mg/mL. All the extracts demonstrated great antioxidant activity, especially in β-carotene-linoleic acid assay and DPPH colorimetric test, where no statistically significant difference in activity of extracts and positive control (BHA) could be detected (p>0.05). Similar results were obtained using EPR free-radical scavenging technique. All the extracts examined were rich in phenols (over 10%, w/w) and total phenol content correlated well with antioxidant activity in all tests (ANOVA, r²>0.9). Water extract of flowers demonstrated highest antioxidant activity. Potent antioxidant activity, together with pronounced antimicrobial activity of ethanolic extract, may support the use of E. angustifolium in treatment of prostatitis and benign prostatic hyperplasia.

References: 1. Steenkamp, V. et al. (2006)J. Ethnopharmacol. 103:71–75.