List of 5α-reductase inhibitors

This is a list of 5α-reductase inhibitors (5α-RIs), drugs which inhibit one or more isoforms of the enzyme 5α-reductase. This enzyme is responsible for the conversion of the androgen hormone testosterone into the more potent dihydrotestosterone (DHT) and is essential for the production of neurosteroids like allopregnanolone, tetrahydrodeoxycorticosterone (THDOC), and 3α-androstanediol from progesterone, deoxycorticosterone, and DHT, respectively. 5α-Reductase inhibitors have medical applications in the treatment of benign prostatic hyperplasia, androgenic alopecia (pattern hair loss), and hirsutism (excessive hair growth).

Pharmaceutical drugs

5α-RIs that are used in medicine include the following:

Alfatradiol (Ell-Cranell Alpha, Pantostin)
Dutasteride (Avodart) – inhibits types 1, 2, and 3
Epristeride (Aipuliete, Chuanliu) – inhibits type 2
Finasteride (Proscar, Propecia) – inhibits types 2 and 3
Isotretinoin (Accutane) - inhibit type 1,2 and 3

Experimental drugs

5α-RIs that were under development for potential clinical use but were never marketed or are used in research include the following:

4-MA – inhibits types 1 and 2 ({{abbrlink|IC₅₀|half-maximal inhibitory concentration}} = 8.5 nM), but also {{abbrlink|3β-HSD|3β-hydroxysteroid dehydrogenase}} inhibitor, investigated extensively but found to be hepatotoxic{{cite journal | vauthors = Guarna A, Occhiato EG, Danza G, Conti A, Serio M | title = 5 alpha-reductase inhibitors, chemical and clinical models | journal = Steroids | volume = 63 | issue = 5–6 | pages = 355–61 | year = 1998 | pmid = 9618802 | doi = 10.1016/S0039-128X(98)00020-8 | s2cid = 54357911 }}
17β-Carboxy-4-androsten-3-one{{cite journal | vauthors = Hsia SL, Voigt W | title = Inhibition of dihydrotestosterone formation: an effective means of blocking androgen action in hamster sebaceous gland | journal = The Journal of Investigative Dermatology | volume = 62 | issue = 3 | pages = 224–7 | date = March 1974 | pmid = 4361987 | doi = 10.1111/1523-1747.ep12676791 | doi-access = free }}
AS-97004
Azelaic Acid
Bexlosteride (LY-300502) – inhibits type 1
CGP-53153
Efomycin G (SNA 4606-2)
EM-402
FCE-28260 – inhibits types 1 and 2
FK-143
FR-146687
G-20000
Izonsteride (LY-320236) – inhibits types 1 and 2
L-10
L-39
L-697818
L-751788 (16-((4-chlorophenyl)oxy)-4,7-dimethyl-4-azaandronstan-3-one)
Lapisteride (CS-891) – inhibits types 1 and 2
LY-191704
LY-266111
MK-386 (L-733692) – inhibits type 1
MK-434 – inhibits type 2{{cite journal | vauthors = Cohen SM, Werrmann JG, Rasmusson GH, Tanaka WK, Malatesta PF, Prahalada S, Jacobs JG, Harris G, Nett TM | title = Comparison of the effects of new specific azasteroid inhibitors of steroid 5 alpha-reductase on canine hyperplastic prostate: suppression of prostatic DHT correlated with prostate regression | journal = The Prostate | volume = 26 | issue = 2 | pages = 55–71 | date = February 1995 | pmid = 7531846 | doi = 10.1002/pros.2990260202 | s2cid = 40758833 }}
MK-963 (L-654066) – inhibits type 2
ONO-3805 (ONO-RI-3805)
PHL-00801 (Prostatonin; PY 102/UR 102; Pygeum africanum/Urtica dioica extract)
PNU-157706 – inhibits types 1 and 2{{cite journal | vauthors = di Salle E, Giudici D, Radice A, Zaccheo T, Ornati G, Nesi M, Panzeri A, Délos S, Martin PM | title = PNU 157706, a novel dual type I and II 5alpha-reductase inhibitor | journal = The Journal of Steroid Biochemistry and Molecular Biology | volume = 64 | issue = 3–4 | pages = 179–86 | date = February 1998 | pmid = 9605412 | doi = 10.1016/S0960-0760(97)00158-1 | s2cid = 54300283 }}
Steroidal oximes{{cite journal | vauthors = Hartmann RW, Hector M, Haidar S, Ehmer PB, Reichert W, Jose J | title = Synthesis and evaluation of novel steroidal oxime inhibitors of P450 17 (17 alpha-hydroxylase/C17-20-lyase) and 5 alpha-reductase types 1 and 2 | journal = Journal of Medicinal Chemistry | volume = 43 | issue = 22 | pages = 4266–77 | date = November 2000 | pmid = 11063622 | doi = 10.1021/jm001008m }}{{cite journal | vauthors = Flores E, Bratoeff E, Cabeza M, Ramirez E, Quiroz A, Heuze I | title = Steroid 5α-Reductase Inhibitors | journal = Mini Reviews in Medicinal Chemistry | volume = 3 | issue = 3 | pages = 225–37 | date = May 2003 | pmid = 12570838 | doi = 10.2174/1389557033488196 }}
Turosteride (FCE-26073) – inhibits type 2 and to a 15-fold lesser extent type 1
Z-350 – also an α₁-adrenergic receptor antagonist{{cite journal | vauthors = Fukuta Y, Fukuda Y, Higashino R, Yoshida K, Ogishima M, Tamaki H, Takei M | title = Z-350, a novel compound with alpha 1-adrenoceptor antagonistic and steroid 5 alpha-reductase inhibitory actions: pharmacological properties in vivo | journal = The Journal of Pharmacology and Experimental Therapeutics | volume = 290 | issue = 3 | pages = 1013–8 | date = September 1999 | pmid = 10454472 }}

Herbs and other inhibitors

Many plants, as well as their associated phytochemical constituents, have inhibitory effects on 5α-reductase.{{cite journal | vauthors = Nahata A, Dixit VK | title = Evaluation of 5α-reductase inhibitory activity of certain herbs useful as antiandrogens | journal = Andrologia | volume = 46 | issue = 6 | pages = 592–601 | date = August 2014 | pmid = 23710567 | doi = 10.1111/and.12115 | s2cid = 36474953 | doi-access = free }} In addition, many of these compounds are also phytoestrogens. Examples include the following:

Lion's Mane mushrooms https://library.uniteddiversity.coop/Permaculture/Mycelium_Running.pdf p.217
Alizarin,{{Citation needed|date=June 2014}}.
Angelica koreana Plants for a Future: [http://digedibles.com/database/plants.php?Angelica+koreana Angelica koreana] {{Webarchive|url=https://web.archive.org/web/20110710124328/http://digedibles.com/database/plants.php?Angelica+koreana |date=2011-07-10 }}{{cite journal | vauthors = Seo EK, Kim KH, Kim MK, Cho MH, Choi E, Kim K, Mar W | title = Inhibitors of 5alpha -reductase type I in LNCaP cells from the roots of Angelica koreana | journal = Planta Medica | volume = 68 | issue = 2 | pages = 162–3 | date = February 2002 | pmid = 11859469 | doi = 10.1055/s-2002-20258 | s2cid = 260278606 }}
Astaxanthin{{Cite journal|last=Anderson|first=Mark L.|date=2005|title=A preliminary investigation of the enzymatic inhibition of 5alpha-reduction and growth of prostatic carcinoma cell line LNCap-FGC by natural astaxanthin and Saw Palmetto lipid extract in vitro|url=https://pubmed.ncbi.nlm.nih.gov/16093232/|journal=Journal of Herbal Pharmacotherapy|volume=5|issue=1|pages=17–26|doi=10.1080/J157v05n01_03 |issn=1522-8940|pmid=16093232|s2cid=22017932 }}
Azelaic acid, (sometimes combined with minoxidil hair solution).
Black Pepper leaf extract (Piper nigrum) {{cite journal | vauthors = Hirata N, Tokunaga M, Naruto S, Iinuma M, Matsuda H | title = Testosterone 5alpha-reductase inhibitory active constituents of Piper nigrum leaf | journal = Biological & Pharmaceutical Bulletin | volume = 30 | issue = 12 | pages = 2402–5 | date = December 2007 | pmid = 18057734 | doi = 10.1248/bpb.30.2402 | doi-access = free }}
β-Sitosterol,{{cite journal | vauthors = Cabeza M, Bratoeff E, Heuze I, Ramírez E, Sánchez M, Flores E | title = Effect of beta-sitosterol as inhibitor of 5 alpha-reductase in hamster prostate | journal = Proceedings of the Western Pharmacology Society | volume = 46 | pages = 153–5 | year = 2003 | pmid = 14699915 }} one of many phytosterols.
Chinese knotweed (Reynoutria multiflora, syn. Polygonum multiflorum),{{cite journal | vauthors = Liu Y, Wang Q, Yang J, Guo X, Liu W, Ma S, Li S | title = Polygonum multiflorum Thunb.: A Review on Chemical Analysis, Processing Mechanism, Quality Evaluation, and Hepatotoxicity | journal = Frontiers in Pharmacology | volume = 9 | issue = 1 | pages = 364 | date = April 2018 | pmid = 29713283 | doi = 10.3389/fphar.2018.00364 | pmc = 5912012 | doi-access = free }} contains resveratrol-like Stilbenoids.
Curcumin,{{Cite journal|title=Inhibitory Effect of Curcumin on Testosterone Induced Benign Prostatic Hyperplasia Rat Model|last1=Sk|first1=Kim|last2=H|first2=Seok|date=2015-10-22|language=en|pmid=26490686|last3=Hj|first3=Park|last4=Hs|first4=Jeon|last5=Sw|first5=Kang|last6=Bc|first6=Lee|last7=J|first7=Yi|last8=Sy|first8=Song|last9=Sh|first9=Lee|journal = BMC Complementary and Alternative Medicine|volume = 15|pages = 380|doi = 10.1186/s12906-015-0825-y|pmc = 4618860 |doi-access=free }}{{Cite journal|last1=Ide|first1=Hisamitsu|last2=Lu|first2=Yan|last3=Noguchi|first3=Takahiro|last4=Muto|first4=Satoru|last5=Okada|first5=Hiroshi|last6=Kawato|first6=Suguru|last7=Horie|first7=Shigeo|date=April 2018|title=Modulation of AKR1C2 by curcumin decreases testosterone production in prostate cancer|journal=Cancer Science|volume=109|issue=4|pages=1230–1238|doi=10.1111/cas.13517|issn=1347-9032|pmc=5891173|pmid=29369461}}{{Cite journal|last1=Srivilai|first1=Jukkarin|last2=Rabgay|first2=Karma|last3=Khorana|first3=Nantaka|last4=Waranuch|first4=Neti|last5=Nuengchamnong|first5=Nitra|last6=Wisuitiprot|first6=Wudtichai|last7=Chuprajob|first7=Thipphawan|last8=Changtam|first8=Chatchawan|last9=Suksamrarn|first9=Apichart|last10=Chavasiri|first10=Warinthorn|last11=Sornkaew|first11=Nilubon|date=2017-07-01|title=Anti-androgenic curcumin analogues as steroid 5-alpha reductase inhibitors|journal=Medicinal Chemistry Research|language=en|volume=26|issue=7|pages=1550–1556|doi=10.1007/s00044-017-1869-y|s2cid=38952839|issn=1554-8120}} the principal curcuminoid of turmeric.
Dodder (Cuscuta reflexa){{cite journal | vauthors = Pandit S, Chauhan NS, Dixit VK | title = Effect of Cuscuta reflexa Roxb on androgen-induced alopecia | journal = Journal of Cosmetic Dermatology | volume = 7 | issue = 3 | pages = 199–204 | date = September 2008 | pmid = 18789055 | doi = 10.1111/j.1473-2165.2008.00389.x | s2cid = 23035110 }}
Eastern arborvitae, northern whitecedar (Thuja occidentalis){{cite journal | vauthors = Park WS, Lee CH, Lee BG, Chang IS | title = The extract of Thujae occidentalis semen inhibited 5alpha-reductase and androchronogenetic alopecia of B6CBAF1/j hybrid mouse | journal = Journal of Dermatological Science | volume = 31 | issue = 2 | pages = 91–8 | date = April 2003 | pmid = 12670719 | doi = 10.1016/s0923-1811(02)00146-9 }}
Euphorbia jolkiniiFlora of China: [http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=250084075 Euphorbia jolkinii]{{cite journal | vauthors = Park SH, Kim JA, Hua XG |title=Isolation of 5α-reductase inhibitors from Euphorbia jolkinii|journal=Korean Journal of Pharmacognosy|year=2005|volume=36|issue=1|pages=9–16}}
Fatty acids: The relative inhibitory potencies of unsaturated fatty acids are, in decreasing order: Gamma-Linolenic acid, alpha-linolenic acid, linoleic acid, palmitoleic acid, oleic acid, and myristoleic acid.{{cite journal | vauthors = Liang T, Liao S | title = Inhibition of steroid 5 alpha-reductase by specific aliphatic unsaturated fatty acids | journal = The Biochemical Journal | volume = 285 ( Pt 2) | issue = 2 | pages = 557–62 | date = July 1992 | pmid = 1637346 | pmc = 1132824 | doi = 10.1042/bj2850557 }}{{cite journal | vauthors = Veeresh B, Patil AA, Warke YB| title = Combination of lauric acid and myristic acid prevents benign prostatic hyperplasia symptoms in animal model | journal = African Journal of Pharmacy and Pharmacology | volume = 10 | issue = 8 | pages = 101–106 | date = February 2016 | pmid = 19786012 | doi = 10.1016/j.ejphar.2009.09.037 }}
Medium chain fatty acids such as those found in coconut and the kernel of many palm fruits have also been found to inhibit 5α-reductase.{{cite journal | vauthors = Liu J, Shimizu K, Kondo R | title = Anti-androgenic activity of fatty acids | journal = Chemistry & Biodiversity | volume = 6 | issue = 4 | pages = 503–12 | date = April 2009 | pmid = 19353546 | doi = 10.1002/cbdv.200800125 | s2cid = 22807048 | doi-access = free }}
Garden balsam or rose balsam (Impatiens balsamina){{cite journal | vauthors = Oku H, Ishiguro K | year = 2002 | title = Cyclooxygenase-2 inhibitory 1,4-naphthoquinones from Impatiens balsamina L. | journal = Biological & Pharmaceutical Bulletin | volume = 25 | issue = 5| pages = 658–60 | doi=10.1248/bpb.25.658| pmid = 12033510 | doi-access = free }}
Green tea catechins, including (-)-epicatechin-3-gallate, and (-)-epigallo-catechin-3-gallate (EGCG).{{cite journal | vauthors = Liao S, Lin J, Dang MT, Zhang H, Kao YH, Fukuchi J, Hiipakka RA | title = Growth suppression of hamster flank organs by topical application of catechins, alizarin, curcumin, and myristoleic acid | journal = Archives of Dermatological Research | volume = 293 | issue = 4 | pages = 200–5 | date = April 2001 | pmid = 11380153 | doi = 10.1007/s004030000203 | s2cid = 27472497 }} However, another research found that green tea may actually increase DHT levels.{{Cite journal |last1=Zhou |first1=J. R. |last2=Yu |first2=L. |last3=Zhong |first3=Y. |last4=Blackburn |first4=G. L. |title=Soy Phytochemicals and Tea Bioactive Components Synergistically Inhibit Androgen-Sensitive Human Prostate Tumors in Mice |year=2003 |journal=The Journal of Nutrition |volume=133 |issue=2 |pages=516–521 |doi=10.1093/jn/133.2.516 |pmc=2683253 |pmid=12566493 |quote=Green tea tended to increase serum testosterone and DHT levels by 73.8% (P = 0.14) and 194% (P = 0.076), respectively}}
Black tea theaflavins {{Cite journal|last1=Zhou|first1=Jin-Rong|last2=Yu|first2=Lunyin|last3=Zhong|first3=Ying|last4=Blackburn|first4=George L.|date=February 2003|title=Soy phytochemicals and tea bioactive components synergistically inhibit androgen-sensitive human prostate tumors in mice|journal=The Journal of Nutrition|volume=133|issue=2|pages=516–521|doi=10.1093/jn/133.2.516|issn=0022-3166|pmc=2683253|pmid=12566493}}{{Cite journal|last1=Lee|first1=Hung-Hsiao|last2=Ho|first2=Chi-Tang|last3=Lin|first3=Jen-Kun|date=July 2004|title=Theaflavin-3,3'-digallate and penta-O-galloyl-beta-D-glucose inhibit rat liver microsomal 5alpha-reductase activity and the expression of androgen receptor in LNCaP prostate cancer cells|journal=Carcinogenesis|volume=25|issue=7|pages=1109–1118|doi=10.1093/carcin/bgh106|issn=0143-3334|pmid=14963012|doi-access=free}}
Japanese hedge parsley (Torilis japonica){{cite journal | vauthors = Park WS, Son ED, Nam GW, Kim SH, Noh MS, Lee BG, Jang IS, Kim SE, Lee JJ, Lee CH | title = Torilin from Torilis japonica, as a new inhibitor of testosterone 5 alpha-reductase | journal = Planta Medica | volume = 69 | issue = 5 | pages = 459–61 | date = May 2003 | pmid = 12802730 | doi = 10.1055/s-2003-39717 | s2cid = 260279018 }}
Ku Shen or Bitter root (Sophora flavescens){{cite journal | vauthors = Roh SS, Kim CD, Lee MH, Hwang SL, Rang MJ, Yoon YK | title = The hair growth promoting effect of Sophora flavescens extract and its molecular regulation | journal = Journal of Dermatological Science | volume = 30 | issue = 1 | pages = 43–9 | date = October 2002 | pmid = 12354419 | doi = 10.1016/s0923-1811(02)00060-9 }}
Lingzhi mushroom or Reishi mushroom (Ganoderma lucidum){{cite journal | vauthors = Fujita R, Liu J, Shimizu K, Konishi F, Noda K, Kumamoto S, Ueda C, Tajiri H, Kaneko S, Suimi Y, Kondo R | title = Anti-androgenic activities of Ganoderma lucidum | journal = Journal of Ethnopharmacology | volume = 102 | issue = 1 | pages = 107–12 | date = October 2005 | pmid = 16029938 | doi = 10.1016/j.jep.2005.05.041 }}{{cite journal | vauthors = Liu J, Kurashiki K, Shimizu K, Kondo R | title = 5alpha-reductase inhibitory effect of triterpenoids isolated from Ganoderma lucidum | journal = Biological & Pharmaceutical Bulletin | volume = 29 | issue = 2 | pages = 392–5 | date = February 2006 | pmid = 16462054 | doi = 10.1248/bpb.29.392 | doi-access = free }}{{cite journal | vauthors = Liu J, Tamura S, Kurashiki K, Shimizu K, Noda K, Konishi F, Kumamoto S, Kondo R | title = Anti-androgen effects of extracts and compounds from Ganoderma lucidum | journal = Chemistry & Biodiversity | volume = 6 | issue = 2 | pages = 231–43 | date = February 2009 | pmid = 19235153 | doi = 10.1002/cbdv.200800019 | s2cid = 205543884 | doi-access = free }}{{cite journal | vauthors = Noguchi M, Kakuma T, Tomiyasu K, Yamada A, Itoh K, Konishi F, Kumamoto S, Shimizu K, Kondo R, Matsuoka K | title = Randomized clinical trial of an ethanol extract of Ganoderma lucidum in men with lower urinary tract symptoms | journal = Asian Journal of Andrology | volume = 10 | issue = 5 | pages = 777–85 | date = September 2008 | pmid = 18097505 | doi = 10.1111/j.1745-7262.2008.00361.x | doi-access = free }}
Ganoderic acid,{{cite journal | vauthors = Liu J, Shiono J, Shimizu K, Kukita A, Kukita T, Kondo R | title = Ganoderic acid DM: anti-androgenic osteoclastogenesis inhibitor | journal = Bioorganic & Medicinal Chemistry Letters | volume = 19 | issue = 8 | pages = 2154–7 | date = April 2009 | pmid = 19289282 | doi = 10.1016/j.bmcl.2009.02.119 }} or Ganoderol B are thought to be the compounds in the mushroom that are specifically active.{{cite journal | vauthors = Liu J, Shimizu K, Konishi F, Kumamoto S, Kondo R | title = The anti-androgen effect of ganoderol B isolated from the fruiting body of Ganoderma lucidum | journal = Bioorganic & Medicinal Chemistry | volume = 15 | issue = 14 | pages = 4966–72 | date = July 2007 | pmid = 17499997 | doi = 10.1016/j.bmc.2007.04.036 }}
Pesticides: Certain pesticides are able to disturb the sex steroid hormone system and to act as antiandrogens.{{cite journal | vauthors = Lo S, King I, Alléra A, Klingmüller D | title = Effects of various pesticides on human 5alpha-reductase activity in prostate and LNCaP cells | journal = Toxicology in Vitro | volume = 21 | issue = 3 | pages = 502–8 | date = April 2007 | pmid = 17218080 | doi = 10.1016/j.tiv.2006.10.016 }}
Phyllanthus emblica{{cite journal | vauthors = Kumar N, Rungseevijitprapa W, Narkkhong NA, Suttajit M, Chaiyasut C | title = 5α-reductase inhibition and hair growth promotion of some Thai plants traditionally used for hair treatment | journal = Journal of Ethnopharmacology | volume = 139 | issue = 3 | pages = 765–71 | date = February 2012 | pmid = 22178180 | doi = 10.1016/j.jep.2011.12.010 }}
Pine (Pinus sp. resin, active substance abietic acid){{cite journal|doi=10.1248/jhs.56.451 | vauthors = Roh SS, Park MK, Kim YU |title=Abietic acid from Resina Pini of Pinus species as a testosterone 5α-reductase inhibitor|journal=Journal of Health Science|year=2010|volume=56|issue=4|pages=451–455|doi-access=free}}
Pollen of Turnip, turnip rape, fast plants, field mustard, or turnip mustard (Brassica rapa){{cite journal | vauthors = Li YH, Yang YF, Li K, Jin LL, Yang NY, Kong DY | title = 5 alpha-reductase and aromatase inhibitory constituents from Brassica rapa L. pollen | journal = Chemical & Pharmaceutical Bulletin | volume = 57 | issue = 4 | pages = 401–4 | date = April 2009 | pmid = 19336936 | doi = 10.1248/cpb.57.401 | doi-access = free }}
Polyphenols{{cite journal | vauthors = Hiipakka RA, Zhang HZ, Dai W, Dai Q, Liao S | title = Structure-activity relationships for inhibition of human 5alpha-reductases by polyphenols | journal = Biochemical Pharmacology | volume = 63 | issue = 6 | pages = 1165–76 | date = March 2002 | pmid = 11931850 | doi = 10.1016/s0006-2952(02)00848-1 }}
Red stinkwood (Pygeum africanum){{cite journal | vauthors = Edgar AD, Levin R, Constantinou CE, Denis L | title = A critical review of the pharmacology of the plant extract of Pygeum africanum in the treatment of LUTS | journal = Neurourology and Urodynamics | volume = 26 | issue = 4 | pages = 458–463 | year = 2007 | pmid = 17397059 | doi = 10.1002/nau.20136 | s2cid = 24774409 }}
Riboflavin (vitamin B2).{{cite journal | vauthors = Nakayama O, Yagi M, Kiyoto S, Okuhara M, Kohsaka M | title = Riboflavin, a testosterone 5 alpha-reductase inhibitor | journal = The Journal of Antibiotics | volume = 43 | issue = 12 | pages = 1615–6 | date = December 1990 | pmid = 2276981 | doi = 10.7164/antibiotics.43.1615 | doi-access = free }}
Saw palmetto (Serenoa repens, active substance possibly lauric acid{{cite journal | vauthors = Raynaud JP, Cousse H, Martin PM | title = Inhibition of type 1 and type 2 5alpha-reductase activity by free fatty acids, active ingredients of Permixon | journal = The Journal of Steroid Biochemistry and Molecular Biology | volume = 82 | issue = 2–3 | pages = 233–9 | date = October 2002 | pmid = 12477490 | doi = 10.1016/S0960-0760(02)00187-5 | s2cid = 27252883 }}){{cite journal | vauthors = Pais P | title = Potency of a novel saw palmetto ethanol extract, SPET-085, for inhibition of 5alpha-reductase II | journal = Advances in Therapy | volume = 27 | issue = 8 | pages = 555–63 | date = August 2010 | pmid = 20623347 | doi = 10.1007/s12325-010-0041-6 | s2cid = 29319920 }}{{cite journal | vauthors = Abe M, Ito Y, Oyunzul L, Oki-Fujino T, Yamada S | title = Pharmacologically relevant receptor binding characteristics and 5alpha-reductase inhibitory activity of free Fatty acids contained in saw palmetto extract | journal = Biological & Pharmaceutical Bulletin | volume = 32 | issue = 4 | pages = 646–50 | date = April 2009 | pmid = 19336899 | doi = 10.1248/bpb.32.646 | doi-access = free }}
The berries of saw palmetto, a small palm native to the south east United States, possess a dual but weak 5a-reductase inhibition activity, due to their high content of phytosterols: β-sitosterol, stigmasterol, lupeol, lupenone, and cycloartenol. The lipido-sterol extract markedly inhibits both the human isoenzymes. Type 1 isoenzyme is noncompetitively (Ki = 7.2 μg/mL) and type 2 isoenzyme uncompetitively (Ki = 4.9 μg/mL) inhibited.{{cite journal | vauthors = Iehlé C, Délos S, Guirou O, Tate R, Raynaud JP, Martin PM | title = Human prostatic steroid 5 alpha-reductase isoforms--a comparative study of selective inhibitors | journal = The Journal of Steroid Biochemistry and Molecular Biology | volume = 54 | issue = 5–6 | pages = 273–9 | date = September 1995 | pmid = 7577710 | doi = 10.1016/0960-0760(95)00134-L | s2cid = 37075222 }} In vitro studies revealed a 5a-reductase inhibition activity of 1:5600 compared to finasteride but is at minimum 1:18000 in vivo. Meaning the 5a-reductase inhibition activity of 1mg finasteride is equal to 18000mg saw palmetto.{{Cite journal|last1=Rhodes|first1=Linda|last2=Primka|first2=Raymond L.|last3=Berman|first3=Charles|last4=Vergult|first4=Gerard|last5=Gabriel|first5=Munir|last6=Pierre-Malice|first6=Marie|last7=Gibelin|first7=Bruno|date=1993|title=Comparison of finasteride (proscar), a 5α reductase inhibitor, and various commercial plant extracts in in vitro and in vivo 5α reductase inhibition|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/pros.2990220107|journal=The Prostate|language=en|volume=22|issue=1|pages=43–51|doi=10.1002/pros.2990220107|pmid=8381228 |s2cid=85193117 |issn=1097-0045}}
Spore of Japanese climbing fern (Lygodium japonicum){{cite journal | vauthors = Matsuda H, Yamazaki M, Naruo S, Asanuma Y, Kubo M | title = Anti-androgenic and hair growth promoting activities of Lygodii spora (spore of Lygodium japonicum) I. Active constituents inhibiting testosterone 5alpha-reductase | journal = Biological & Pharmaceutical Bulletin | volume = 25 | issue = 5 | pages = 622–6 | date = May 2002 | pmid = 12033503 | doi = 10.1248/bpb.25.622 | doi-access = free }}
Valoneic acid dilactone and gallagyldilactone are two hydrolysable tannin polyphenols isolated from the heartwood of Shorea laevifolia{{cite journal | first1 = Hirano | last1 = Yoshio | first2 = Kondo | last2 = Ryuichiro | first3 = Sakai | last3 = Kokki | name-list-style = vanc | year = 2003| title = 5A-Reductase inhibitory tannin-related compounds isolated from Shorea laevifolia | journal = Journal of Wood Science | volume = 49 | issue = 4| pages = 339–343 | doi=10.1007/s10086-002-0481-y| s2cid = 27915791 | doi-access = free }} and the North American white oak (Quercus alba) and European red oak (Quercus robur) and are inhibitory.{{cite journal | vauthors = Mämmelä P, Savolainen H, Lindroos L, Kangas J, Vartiainen T | title = Analysis of oak tannins by liquid chromatography-electrospray ionisation mass spectrometry | journal = Journal of Chromatography A | volume = 891 | issue = 1 | pages = 75–83 | date = September 2000 | pmid = 10999626 | doi = 10.1016/S0021-9673(00)00624-5 }}
Zinc.{{cite journal | vauthors = Stamatiadis D, Bulteau-Portois MC, Mowszowicz I | title = Inhibition of 5 alpha-reductase activity in human skin by zinc and azelaic acid | journal = The British Journal of Dermatology | volume = 119 | issue = 5 | pages = 627–32 | date = November 1988 | pmid = 3207614 | doi = 10.1111/j.1365-2133.1988.tb03474.x | s2cid = 28506969 }}

These supplements have limited testing in human clinical trials, and their potential for the treatment of BPH, androgenic alopecia, and related conditions is unknown.

References

Category:5α-Reductase inhibitors