Determination of the potency of a novel saw palmetto supercritical CO2 extract (SPSE) for 5α-reductase isoform II inhibition using a cell-free in vitro test system

Abstract

BackgroundThe nicotinamide adenine dinucleotide phosphate-dependent membrane protein 5α-reductase catalyses the conversion of testosterone to the most potent androgen – 5α-dihydrotestosterone. Two 5α-reductase isoenzymes are expressed in humans: type I and type II. The latter is found primarily in prostate tissue. Saw palmetto extract (SPE) has been used extensively in the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH). The pharmacological effects of SPE include the inhibition of 5α-reductase, as well as anti-inflammatory and antiproliferative effects. Clinical studies of SPE have been inconclusive – some have shown significant results, and others have not – possibly the result of varying bioactivities of the SPEs used in the studies.PurposeTo determine the in vitro potency in a cell-free test system of a novel SP supercritical CO2 extract (SPSE), an inhibitor of the 5α-reductase isoenzyme type II.Materials and methodsThe inhibitory potency of SPSE was compared to that of finasteride, an approved 5α-reductase inhibitor, on the basis of the enzymatic conversion of the substrate androstenedione to the 5α-reduced product 5α-androstanedione.ResultsBy concentration-dependent inhibition of 5α-reductase type II in vitro (half-maximal inhibitory concentration 3.58±0.05 μg/mL), SPSE demonstrated competitive binding toward the active site of the enzyme. Finasteride, the approved 5α-reductase inhibitor tested as positive control, led to 63%–75% inhibition of 5α-reductase type II.ConclusionSPSE effectively inhibits the enzyme that has been linked to BPH, and the amount of extract required for activity is comparatively low. It can be confirmed from the results of this study that SPSE has bioactivity that promotes prostate health at a level that is superior to that of many other phytotherapeutic extracts. The bioactivity of SPSE corresponds favorably to that reported for the hexane extract used in a large number of positive BPH clinical trials, as well as to finasteride, the established standard of therapy among prescription drugs. Future in vitro and clinical trials involving SPEs would be useful for elucidating their comparative differences, as well as appropriate patient selection for their use.

A phytosterol-enriched saw palmetto supercritical CO2 extract ameliorates testosterone-induced benign prostatic hyperplasia by regulating the inflammatory and apoptotic proteins in a rat model

“…In another study saw palmetto whole berry and extract were demonstrated to have efficacy in influencing BPH by reducing the androgen-induced prostate enlargement [22]. Recently, Pais et al reported the 5-α reductase inhibitory potential of saw palmetto supercritical CO 2 extract using a cell-free in vitro test system [23]. The present study was conducted to evaluate the efficacy of VISPO, a novel supercritical CO 2 extract of saw palmetto fruits with higher β-sitosterol content (3%).…”