The Willow herb is considered a common weed but may have potential benefit in prostate disorders. Oenothein B, a substance in willow herb, appears to have 5-alpha-reductase inhibitory activity.

Willow Herb Research
Biol Res Nurs. 2012. Gram-negative and gram-positive antibacterial properties of the whole plant extract of willow herb (Epilobium angustifolium).

Acta Pharm Hung. 2009. Epilobium parviflorum --in vitro study of biological action. Willow herb is used for the treatment of benign prostatic hyperplasia (BPH), but its biological action is not entirely identified. This paper aims to report data on willow-herbs probable biological effect. In vitro studies have been made to investigate different aspects of its antioxidant capacity, anti-inflammatory (COX-inhibitory) action, steroid-receptor -agonistic and -antagonostic effect as well as aromatase-inhibitory effect. Based on our results, willow herb has remarkable antioxidant and COX-inhibitory action.

Studies on antibacterial, anti-inflammatory and antioxidant activity of herbal remedies used in the treatment of benign prostatic hyperplasia and prostatitis.
J Ethnopharmacol. 2006. Department of Urology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
Crude water and ethanolic extracts of five herbal remedies reported in the literature for traditional treatment of benign prostatic hyperplasia (BPH) and/or prostatitis were investigated for their effect on hydroxyl scavenging activity, antibacterial activity and their ability to inhibit cyclooxygenase-1 and -2 (COX-1 and COX-2) catalysed prostaglandin biosynthesis. Both the water and ethanol extracts of Hypoxis hemerocallidea and Epilobium parviflorum inhibited the growth of Escherichia coli. All 10 extracts scavenged the hydroxyl radical but with various potencies (32-93%). Ethanolic extracts were the most active in inhibiting COX-1 catalysed prostaglandin biosynthesis. The ethanolic extract of Epilobium parviflorum showed inhibitory effects on both the COX-1 and -2 catalysed prostaglandin biosynthesis, inhibited growth of Escherichia coli and exerted antioxidant activity. Although these results support the traditional use of Epilobium parviflorum for treatment of prostatitis and BPH, further investigation is required, for this promising plant.

Determination of oenothein B as the active 5-alpha-reductase-inhibiting principle of the folk medicine Epilobium parviflorum.
J Nat Prod. 1996. Centre de Recherche ROUSSEL UCLAF, Roumainville, France.
Several extracts from Epilobium parviflorum, the willow herb plant used in Central Europe for the treatment of prostate disorders, were evaluated in a biochemical assay with 5-alpha-reductase. The aqueous willow herb extract displaying inhibition of the enzyme was analyzed, the fraction responsible for this activity was purified, and the active compound identified as a macrocyclic tannin, oenothein B.

Willow Herb questions
Q. Can willow herb be used the same time as ahcc supplement?
   A. We have not seen any studies with this combination, so it is difficult to say for sure. Many herbs and supplements can be combined safely if the dosage used of each is low.

Having read of aspirin daily doses against cancer of digestive tract (I'm 62 and grandfather had colon cancer, dad had esophageal cancer), and being a huge consumer of garlic, could I take willow bark essence and would it be gentler than aspirin in terms of colon cancer prevention but with same effect?
   I have seen no research on this topic to know whether it would offer such benefit, and even if it did what the ideal dosage or form would be.