Uromedic® Pumpkin Seed Derived Δ7-Sterols, Extract and Oil Inhibit 5α-Reductases and Bind to Androgen Receptor <em>in Vitro</em>

Abstract

Dihydrotestosterone (DHT) is implicated in the development of benign prostate hyperplasia (BPH). We investigated if Uromedic ? pumpkin (variety of Cucurbita pepo L. convar. citrullinina GREB. var. styriaca GREB ) seed soft extract (active ingredients of GRANUFINK ? Prosta forte 500 mg), seed oil and isolated Δ7-sterols could inhibit the conversion of [1,2,6,7- 3 H(N)]-testosterone to DHT by 5 α -reductases. Also, we tested competition with [ 3 H]-DHT for binding to the androgen receptor (AR). Pumpkin seed oil and pumpkin seed soft extract were identified as moderately active inhibitors of 5 α -R1 and 5 α -R2, with almost similar inhibitory capacities (IC 50 < 5 mg/ml for 5 α -R1 and about IC 50 = 6 mg/ml for 5 α -R2). The isolated Δ7-sterols were more active inhibitors (IC 50 = 0.3 mg/ml for 5 α -R1, IC 50 = 1.0 mg/ml for 5 α -R2). All three test compounds bound to the AR dose-dependently, with strong binding by Δ7-sterols (IC 50 = 0.2 mg/ml) and weaker binding by pumpkin seed oil (IC 50 = 0.4 mg/ml) and pumpkin seed soft extract (IC 50 = 1.1 mg/ml). We propose that inhibition of 5 α -reductases and competitive binding to the AR are mechanisms of action, by which the Uromedic ? pumpkin seed derived test compounds, most specifically Δ7-sterols, counteract DHT and thereby exert clinically positive effects on the prostate, as well as bladder-strengthening effects.