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2D Structure
Also known as: 62571-86-2, Capoten, L-captopril, Lopirin, Captopryl, Garranil
Molecular Formula
C9H15NO3S
Molecular Weight
217.29  g/mol
InChI Key
FAKRSMQSSFJEIM-RQJHMYQMSA-N
FDA UNII
9G64RSX1XD

A potent and specific inhibitor of PEPTIDYL-DIPEPTIDASE A. It blocks the conversion of ANGIOTENSIN I to ANGIOTENSIN II, a vasoconstrictor and important regulator of arterial blood pressure. Captopril acts to suppress the RENIN-ANGIOTENSIN SYSTEM and inhibits pressure responses to exogenous angiotensin.
Captopril is an Angiotensin Converting Enzyme Inhibitor. The mechanism of action of captopril is as an Angiotensin-converting Enzyme Inhibitor.
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
(2S)-1-[(2S)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic acid
2.1.2 InChI
InChI=1S/C9H15NO3S/c1-6(5-14)8(11)10-4-2-3-7(10)9(12)13/h6-7,14H,2-5H2,1H3,(H,12,13)/t6-,7+/m1/s1
2.1.3 InChI Key
FAKRSMQSSFJEIM-RQJHMYQMSA-N
2.1.4 Canonical SMILES
CC(CS)C(=O)N1CCCC1C(=O)O
2.1.5 Isomeric SMILES
C[C@H](CS)C(=O)N1CCC[C@H]1C(=O)O
2.2 Other Identifiers
2.2.1 UNII
9G64RSX1XD
2.3 Synonyms
2.3.1 MeSH Synonyms

1. (s)-1-(3-mercapto-2-methyl-1-oxopropyl)-l-proline

2. Capoten

3. Lopirin

4. Sq 14,225

5. Sq 14,534

6. Sq 14225

7. Sq 14534

8. Sq-14,225

9. Sq-14,534

10. Sq-14225

11. Sq-14534

12. Sq14,225

13. Sq14,534

14. Sq14225

15. Sq14534

2.3.2 Depositor-Supplied Synonyms

1. 62571-86-2

2. Capoten

3. L-captopril

4. Lopirin

5. Captopryl

6. Garranil

7. Cesplon

8. Captolane

9. Tensoprel

10. Acepress

11. Captoril

12. Dilabar

13. Hypertil

14. Tenosbon

15. Alopresin

16. Captoprilum

17. Acepril

18. Apopril

19. Lopril

20. Acediur

21. Aceplus

22. (2s)-1-[(2s)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic Acid

23. Sq-14225

24. Farcopril

25. Hypopress

26. Tensiomin

27. Tensobon

28. Zapto

29. Captoprilum [inn-latin]

30. Sq 14225

31. D-2-methyl-3-mercaptopropanoyl-l-proline

32. D-3-mercapto-2-methylpropanoyl-l-proline

33. Sq 14,225

34. 1-((2s)-3-mercapto-2-methylpropionyl)-l-proline

35. Sa 333

36. D-3-mercapto-2-methylpropionylproline

37. Captomax

38. Mepha

39. L-proline, 1-[(2s)-3-mercapto-2-methyl-1-oxopropyl]-

40. 1-[(2s)-2-methyl-3-sulfanylpropanoyl]-l-proline

41. (2s)-1-(3-mercapto-2-methylpropionyl)-l-proline

42. Hipertil

43. Chebi:3380

44. C09aa01

45. L-proline, 1-(3-mercapto-2-methyl-1-oxopropyl)-, (s)-

46. Nsc-757419

47. 9g64rsx1xd

48. Chembl1560

49. 1-[(2s)-3-mercapto-2-methyl-1-oxopropyl]-l-proline

50. Mls000069484

51. Asisten

52. Isopresol

53. (s)-1-((s)-3-mercapto-2-methylpropanoyl)pyrrolidine-2-carboxylic Acid

54. (-)-captopril

55. 1-(3-mercapto-2-methyl-1-oxopropyl)-l-proline

56. Sa-333

57. (s)-1-(3-mercapto-2-methyl-1-oxopropyl)-l-proline

58. L-proline, 1-((2s)-3-mercapto-2-methyl-1-oxopropyl)-

59. Ncgc00023654-04

60. Smr000059061

61. Sq -14225

62. Lopirin [switzerland]

63. 1-pyrrolidinecarboxylic Acid, 1-(d-3-mercapto-2-methyl-1-propionyl)-, L-(s,s)-

64. Dsstox_cid_17197

65. Dsstox_rid_79306

66. Dsstox_gsid_37197

67. Novocaptopril

68. Captril

69. Captopril (capoten)

70. Capozide (salt/mix)

71. 3-mercapto-2-methylpropionyl-proline

72. X8z

73. Apopril (tn)

74. Capoten (tn)

75. Hsdb 6527

76. 1-[(2s)-3-mercapto-2-methylpropionyl]-l-proline

77. Sr-01000075603

78. Einecs 263-607-1

79. Unii-9g64rsx1xd

80. Component Of Captea (salt/mix)

81. Component Of Acezide (salt/mix)

82. Component Of Ecazide (salt/mix)

83. 1-(d-3-mercapto-2-methyl-1-oxopropyl)-l-proline (s,s)

84. Captopril,(s)

85. Prestwick_103

86. Capoten;l-captopril

87. Mfcd00168073

88. Captopril [usan:usp:inn:ban:jan]

89. Sq14534

90. Schembl4

91. Spectrum_000688

92. Captopril [inn]

93. Captopril [jan]

94. Captopril [mi]

95. Captopril [hsdb]

96. Captopril [usan]

97. Opera_id_1041

98. Prestwick3_000019

99. Spectrum2_001211

100. Spectrum3_001388

101. Spectrum4_000811

102. Spectrum5_001587

103. Captopril [vandf]

104. Lopac-c-4042

105. 1-((2s)-2-methyl-3-sulfanylpropanoyl)-l-proline #

106. Captopril [mart.]

107. Epitope Id:114065

108. Upcmld-dp003

109. C 4042

110. Captopril [usp-rs]

111. Captopril [who-dd]

112. Captopril [who-ip]

113. Lopac0_000302

114. Bspbio_000057

115. Bspbio_002976

116. Kbiogr_001321

117. Kbioss_001168

118. Mls001076488

119. Divk1c_000208

120. Spectrum1500682

121. Spbio_001022

122. Captopril (jp17/usp/inn)

123. (s)-1-(3-mercapto-2-methyl-1-oxo-propyl)-l-proline

124. Bpbio1_000063

125. Gtpl5158

126. Captopril [orange Book]

127. Captopril For System Suitability

128. Captopril [ep Monograph]

129. Captopril [usp Impurity]

130. Dtxsid1037197

131. Upcmld-dp003:001

132. Bdbm21642

133. Hms500k10

134. Kbio1_000208

135. Kbio2_001168

136. Kbio2_003736

137. Kbio2_006304

138. Kbio3_002196

139. Zinc57001

140. Captopril [usp Monograph]

141. 1j37

142. Ninds_000208

143. Hms1921c12

144. Hms2089p19

145. Hms2092i12

146. Hms2095c19

147. Hms2233i04

148. Hms3259g10

149. Hms3260n06

150. Hms3712c19

151. Pharmakon1600-01500682

152. Sa333

153. Captoprilum [who-ip Latin]

154. Hy-b0368

155. Tox21_110890

156. Tox21_500302

157. Bbl033600

158. Ccg-39104

159. Ei-213

160. Nsc757419

161. S2051

162. Stk802012

163. Captopril 100 Microg/ml In Methanol

164. Akos005622581

165. Captopril, >=98% (hplc), Powder

166. Tox21_110890_1

167. Bcp9000485

168. Cs-2425

169. Db01197

170. Ks-5025

171. Lp00302

172. Nc00554

173. Nsc 757419

174. Sdccgsbi-0050290.p006

175. Idi1_000208

176. Smp1_000056

177. Ncgc00015235-01

178. Ncgc00015235-02

179. Ncgc00023654-03

180. Ncgc00023654-05

181. Ncgc00023654-06

182. Ncgc00023654-07

183. Ncgc00023654-08

184. Ncgc00023654-09

185. Ncgc00023654-10

186. Ncgc00023654-11

187. Ncgc00023654-13

188. Ncgc00023654-25

189. Ncgc00023654-26

190. Ncgc00260987-01

191. Ac-12047

192. Ac-32120

193. Sbi-0050290.p004

194. Captopril, Meets Usp Testing Specifications

195. Eu-0100302

196. ((s)-3-mercapto-2-methylpropanoyl)-l-proline

197. Bim-0050290.0001

198. C06867

199. D00251

200. Ab00052156-16

201. Ab00052156_17

202. Ab00052156_18

203. 571c862

204. Q421119

205. Sr-01000000039

206. 1-[(2s)-3-mercapto-2-methylpropionyl]- L-proline

207. Sr-01000000039-2

208. Sr-01000075603-1

209. Sr-01000075603-3

210. 1-[(s)-3-mercapto-2-methyl-1-oxopropyl]-l-proline

211. Brd-k54529596-001-04-0

212. Brd-k54529596-001-15-6

213. Captopril, British Pharmacopoeia (bp) Reference Standard

214. Z2786051697

215. Captopril, European Pharmacopoeia (ep) Reference Standard

216. Captopril, United States Pharmacopeia (usp) Reference Standard

217. (s)-1-((s)-3-mercapto-2-methylpropanoyl)pyrrolidine-2-carboxylicacid

218. Captopril, Pharmaceutical Secondary Standard; Certified Reference Material

219. L-?proline, 1-?[(2s)?-?3-?mercapto-?2-?methyl-?1-?oxopropyl]?-

220. Captopril For System Suitability, European Pharmacopoeia (ep) Reference Standard

2.4 Create Date
2005-06-24
3 Chemical and Physical Properties
Molecular Weight 217.29 g/mol
Molecular Formula C9H15NO3S
XLogP30.3
Hydrogen Bond Donor Count2
Hydrogen Bond Acceptor Count4
Rotatable Bond Count3
Exact Mass217.07726451 g/mol
Monoisotopic Mass217.07726451 g/mol
Topological Polar Surface Area58.6 Ų
Heavy Atom Count14
Formal Charge0
Complexity244
Isotope Atom Count0
Defined Atom Stereocenter Count2
Undefined Atom Stereocenter Count0
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Drug Information
1 of 4  
Drug NameCapoten
PubMed HealthCaptopril (By mouth)
Drug ClassesAntihypertensive, Cardiovascular Agent, Renal Protective Agent
Drug LabelCaptopril is a specific competitive inhibitor of angiotensin I-converting enzyme (ACE), the enzyme responsible for the conversion of angiotensin I to angiotensin II.Captopril is designated chemically as 1-[(2S)-3-mercapto-2-methylpropionyl]-L-proline...
Active IngredientCaptopril
Dosage FormTablet
RouteOral
Strength100mg; 25mg; 50mg; 12.5mg
Market StatusPrescription
CompanyPar Pharm

2 of 4  
Drug NameCaptopril
PubMed HealthCaptopril (By mouth)
Drug ClassesAntihypertensive, Cardiovascular Agent, Renal Protective Agent
Active IngredientCaptopril
Dosage FormTablet
RouteOral
Strength100mg; 25mg; 50mg; 12.5mg
Market StatusPrescription
CompanyWatson Labs; Wockhardt; Teva; Apotex; Sandoz; Hikma Pharms; Mylan; Stason

3 of 4  
Drug NameCapoten
PubMed HealthCaptopril (By mouth)
Drug ClassesAntihypertensive, Cardiovascular Agent, Renal Protective Agent
Drug LabelCaptopril is a specific competitive inhibitor of angiotensin I-converting enzyme (ACE), the enzyme responsible for the conversion of angiotensin I to angiotensin II.Captopril is designated chemically as 1-[(2S)-3-mercapto-2-methylpropionyl]-L-proline...
Active IngredientCaptopril
Dosage FormTablet
RouteOral
Strength100mg; 25mg; 50mg; 12.5mg
Market StatusPrescription
CompanyPar Pharm

4 of 4  
Drug NameCaptopril
PubMed HealthCaptopril (By mouth)
Drug ClassesAntihypertensive, Cardiovascular Agent, Renal Protective Agent
Active IngredientCaptopril
Dosage FormTablet
RouteOral
Strength100mg; 25mg; 50mg; 12.5mg
Market StatusPrescription
CompanyWatson Labs; Wockhardt; Teva; Apotex; Sandoz; Hikma Pharms; Mylan; Stason

4.2 Therapeutic Uses

Angiotensin-Converting Enzyme Inhibitors; Antihypertensive Agents

National Library of Medicine's Medical Subject Headings. Captopril. Online file (MeSH, 2017). Available from, as of August 30, 2017: https://www.nlm.nih.gov/mesh/2017/mesh_browser/MBrowser.html


/CLINICAL TRIALS/ ClinicalTrials.gov is a registry and results database of publicly and privately supported clinical studies of human participants conducted around the world. The Web site is maintained by the National Library of Medicine (NLM) and the National Institutes of Health (NIH). Each ClinicalTrials.gov record presents summary information about a study protocol and includes the following: Disease or condition; Intervention (for example, the medical product, behavior, or procedure being studied); Title, description, and design of the study; Requirements for participation (eligibility criteria); Locations where the study is being conducted; Contact information for the study locations; and Links to relevant information on other health Web sites, such as NLM's MedlinePlus for patient health information and PubMed for citations and abstracts for scholarly articles in the field of medicine. Captopril is included in the database.

NIH/NLM; ClinicalTrials.Gov. Available from, as of August 30, 2017: https://clinicaltrials.gov/


Captopril tablets are indicated for the treatment of hypertension. ... Captopril tablets are effective alone and in combination with other antihypertensive agents, especially thiazide-type diuretics. The blood pressure lowering effects of captopril and thiazides are approximately additive. /Included in US product label/

NIH; DailyMed. Current Medication Information for Captopril (Captopril Tablet) (Updated: August 2017). Available from, as of October 27, 2017: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5599d8f8-efc8-4acc-a507-280b89fd1dda


Captopril tablets are indicated in the treatment of congestive heart failure usually in combination with diuretics and digitalis. The beneficial effect of captopril in heart failure does not require the presence of digitalis, however, most controlled clinical trial experience with captopril has been in patients receiving digitalis, as well as diuretic treatment. /Included in US product label/

NIH; DailyMed. Current Medication Information for Captopril (Captopril Tablet) (Updated: August 2017). Available from, as of October 27, 2017: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5599d8f8-efc8-4acc-a507-280b89fd1dda


For more Therapeutic Uses (Complete) data for Captopril (11 total), please visit the HSDB record page.


4.3 Drug Warning

/BOXED WARNING/ WARNING: FETAL TOXICITY. When pregnancy is detected, discontinue captopril tablets as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus.

NIH; DailyMed. Current Medication Information for Captopril (Captopril Tablet) (Updated: August 2017). Available from, as of October 27, 2017: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5599d8f8-efc8-4acc-a507-280b89fd1dda


Captopril is generally well tolerated in most patients; however, serious adverse effects (e.g., neutropenia, agranulocytosis, proteinuria, aplastic anemia) have been reported rarely, mainly in patients with renal impairment (especially those with collagen vascular disease). Captopril- induced adverse effects are often alleviated by dosage reduction, occasionally disappear despite continued treatment and without dosage reduction, and are usually reversible following discontinuance of the drug. The most common adverse effects of captopril are rash and loss of taste perception. Adverse effects requiring discontinuance of captopril therapy occur in about 4-12% of patients.

American Society of Health-System Pharmacists 2017; Drug Information 2017. Bethesda, MD. 2017, p. 2074


Captopril is contraindicated in patients with known hypersensitivity to the drug or to another angiotension-converting enzyme inhibitor (eg, those who experienced angioedema during therapy with another angiotension-converting enzyme inhibitor).

American Society of Health-System Pharmacists 2017; Drug Information 2017. Bethesda, MD. 2017, p. 2077


Patients receiving captopril should be warned not to interrupt or discontinue therapy unless instructed by their physician. Patients with congestive heart failure receiving captopril should be cautioned against rapid increases in physical activity.

American Society of Health-System Pharmacists 2017; Drug Information 2017. Bethesda, MD. 2017, p. 2077


For more Drug Warnings (Complete) data for Captopril (32 total), please visit the HSDB record page.


4.4 Minimum/Potential Fatal Human Dose

A case of a 75 year old male who committed suicide by taking an overdose of captopril was reported. He took approximately ninety 12.5 mg captopril tablets. ...

PMID:2231837 Park H et al; J Toxicol Clin Toxicol 28 (3): 379-82 (1990)


4.5 Drug Indication

For the treatment of essential or renovascular hypertension (usually administered with other drugs, particularly thiazide diuretics). May be used to treat congestive heart failure in combination with other drugs (e.g. cardiac glycosides, diuretics, β-adrenergic blockers). May improve survival in patients with left ventricular dysfunction following myocardial infarction. May be used to treat nephropathy, including diabetic nephropathy.


Treatment of heart failure


5 Pharmacology and Biochemistry
5.1 Pharmacology

Captopril, an ACE inhibitor, antagonizes the effect of the RAAS. The RAAS is a homeostatic mechanism for regulating hemodynamics, water and electrolyte balance. During sympathetic stimulation or when renal blood pressure or blood flow is reduced, renin is released from the granular cells of the juxtaglomerular apparatus in the kidneys. In the blood stream, renin cleaves circulating angiotensinogen to ATI, which is subsequently cleaved to ATII by ACE. ATII increases blood pressure using a number of mechanisms. First, it stimulates the secretion of aldosterone from the adrenal cortex. Aldosterone travels to the distal convoluted tubule (DCT) and collecting tubule of nephrons where it increases sodium and water reabsorption by increasing the number of sodium channels and sodium-potassium ATPases on cell membranes. Second, ATII stimulates the secretion of vasopressin (also known as antidiuretic hormone or ADH) from the posterior pituitary gland. ADH stimulates further water reabsorption from the kidneys via insertion of aquaporin-2 channels on the apical surface of cells of the DCT and collecting tubules. Third, ATII increases blood pressure through direct arterial vasoconstriction. Stimulation of the Type 1 ATII receptor on vascular smooth muscle cells leads to a cascade of events resulting in myocyte contraction and vasoconstriction. In addition to these major effects, ATII induces the thirst response via stimulation of hypothalamic neurons. ACE inhibitors inhibit the rapid conversion of ATI to ATII and antagonize RAAS-induced increases in blood pressure. ACE (also known as kininase II) is also involved in the enzymatic deactivation of bradykinin, a vasodilator. Inhibiting the deactivation of bradykinin increases bradykinin levels and may sustain its effects by causing increased vasodilation and decreased blood pressure.


5.2 MeSH Pharmacological Classification

Angiotensin-Converting Enzyme Inhibitors

A class of drugs whose main indications are the treatment of hypertension and heart failure. They exert their hemodynamic effect mainly by inhibiting the renin-angiotensin system. They also modulate sympathetic nervous system activity and increase prostaglandin synthesis. They cause mainly vasodilation and mild natriuresis without affecting heart rate and contractility. (See all compounds classified as Angiotensin-Converting Enzyme Inhibitors.)


Antihypertensive Agents

Drugs used in the treatment of acute or chronic vascular HYPERTENSION regardless of pharmacological mechanism. Among the antihypertensive agents are DIURETICS; (especially DIURETICS, THIAZIDE); ADRENERGIC BETA-ANTAGONISTS; ADRENERGIC ALPHA-ANTAGONISTS; ANGIOTENSIN-CONVERTING ENZYME INHIBITORS; CALCIUM CHANNEL BLOCKERS; GANGLIONIC BLOCKERS; and VASODILATOR AGENTS. (See all compounds classified as Antihypertensive Agents.)


5.3 FDA Pharmacological Classification
5.3.1 Active Moiety
CAPTOPRIL
5.3.2 FDA UNII
9G64RSX1XD
5.3.3 Pharmacological Classes
Angiotensin-converting Enzyme Inhibitors [MoA]; Angiotensin Converting Enzyme Inhibitor [EPC]
5.4 ATC Code

C09AA01

S76 | LUXPHARMA | Pharmaceuticals Marketed in Luxembourg | Pharmaceuticals marketed in Luxembourg, as published by d'Gesondheetskeess (CNS, la caisse nationale de sante, www.cns.lu), mapped by name to structures using CompTox by R. Singh et al. (in prep.). List downloaded from https://cns.public.lu/en/legislations/textes-coordonnes/liste-med-comm.html. Dataset DOI:10.5281/zenodo.4587355


C - Cardiovascular system

C09 - Agents acting on the renin-angiotensin system

C09A - Ace inhibitors, plain

C09AA - Ace inhibitors, plain

C09AA01 - Captopril


5.5 Absorption, Distribution and Excretion

Absorption

60-75% in fasting individuals; food decreases absorption by 25-40% (some evidence indicates that this is not clinically significant)


The drug /captopril/ is metabolized and renally excreted. More than 95% of a dose is excreted renally, both as unchanged (45-50%) drug and as metabolites.

Plumb D.C. Veterinary Drug Handbook. 8th ed. (pocket). Ames, IA: Wiley-Blackwell, 2015., p. 206


In dogs, approximately 75% of an oral dose is absorbed but food in the GI tract reduces bioavailability by 30-40%. It is distributed to most tissues (not the CNS) and is 40% bound to plasma proteins in dogs.

Plumb D.C. Veterinary Drug Handbook. 8th ed. (pocket). Ames, IA: Wiley-Blackwell, 2015., p. 206


Approximately 60-75% of an oral dose of captopril is rapidly absorbed from the GI tract in fasting healthy individuals or hypertensive patients. Food may decrease absorption of captopril by up to 25-40%, although there is some evidence that this effect is not clinically important. Following oral administration of a single 100-mg dose of captopril in fasting healthy individuals in one study, average peak blood drug concentrations of 800 ng/mL were attained in 1 hour.

American Society of Health-System Pharmacists 2017; Drug Information 2017. Bethesda, MD. 2017, p. 2079


/MILK/ Concentrations of captopril in human milk are approximately one percent of those in maternal blood.

NIH; DailyMed. Current Medication Information for Captopril (Captopril Tablet) (Updated: August 2017). Available from, as of October 27, 2017: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5599d8f8-efc8-4acc-a507-280b89fd1dda


For more Absorption, Distribution and Excretion (Complete) data for Captopril (7 total), please visit the HSDB record page.


5.6 Metabolism/Metabolites

Hepatic. Major metabolites are captopril-cysteine disulfide and the disulfide dimer of captopril. Metabolites may undergo reversible interconversion.


About half the absorbed dose of captopril is rapidly metabolized, mainly to captopril-cysteine disulfide and the disulfide dimer of captopril. In vitro studies suggest that captopril and its metabolites may undergo reversible interconversions. It has been suggested that the drug may be more extensively metabolized in patients with renal impairment than in patients with normal renal function.

American Society of Health-System Pharmacists 2017; Drug Information 2017. Bethesda, MD. 2017, p. 2079


5.7 Biological Half-Life

2 hours


A 43 year old patient with mild heart failure attempted suicide by ingesting between 5000 and 7500 mg of captopril. Blood pressure oscillated around 100-120/50-75 mm Hg and pulse rate showed no tendency to accelerate (75-100/min). ... The calculated half-life of captopril was 4.4 hr. ...

PMID:2148447 Lechleitner P et al; Toxicology 64 (3): 325-9 (1990)


The half life of captopril is about 2.8 hours in dogs ... .

Plumb D.C. Veterinary Drug Handbook. 8th ed. (pocket). Ames, IA: Wiley-Blackwell, 2015., p. 206


The elimination half-life of unchanged captopril appears to be less than 2 hours in patients with normal renal function. The elimination half-life of captopril and its metabolites is correlated with creatinine clearance and increases to about 20-40 hours in patients with creatinine clearances less than 20 mL/minute and as long as 6.5 days in anuric patients.

American Society of Health-System Pharmacists 2017; Drug Information 2017. Bethesda, MD. 2017, p. 2079


5.8 Mechanism of Action

There are two isoforms of ACE: the somatic isoform, which exists as a glycoprotein comprised of a single polypeptide chain of 1277; and the testicular isoform, which has a lower molecular mass and is thought to play a role in sperm maturation and binding of sperm to the oviduct epithelium. Somatic ACE has two functionally active domains, N and C, which arise from tandem gene duplication. Although the two domains have high sequence similarity, they play distinct physiological roles. The C-domain is predominantly involved in blood pressure regulation while the N-domain plays a role in hematopoietic stem cell differentiation and proliferation. ACE inhibitors bind to and inhibit the activity of both domains, but have much greater affinity for and inhibitory activity against the C-domain. Captopril, one of the few ACE inhibitors that is not a prodrug, competes with ATI for binding to ACE and inhibits and enzymatic proteolysis of ATI to ATII. Decreasing ATII levels in the body decreases blood pressure by inhibiting the pressor effects of ATII as described in the Pharmacology section above. Captopril also causes an increase in plasma renin activity likely due to a loss of feedback inhibition mediated by ATII on the release of renin and/or stimulation of reflex mechanisms via baroreceptors. Captoprils affinity for ACE is approximately 30,000 times greater than that of ATI.


The local role of the renin angiotensin system (RAS) was documented recently beside its conventional systemic functions. Studies showed that the effector angiotensin II (AngII) alters bone health, while inhibition of the angiotensin converting enzyme (ACE-1) preserved these effects. The newly identified Ang1-7 exerts numerous beneficial effects opposing the AngII. Thus, the current study examines the role of Ang1-7 in mediating the osteo-preservative effects of ACEI (captopril) through the G-protein coupled Mas receptor using an ovariectomized (OVX) rat model of osteoporosis. 8 weeks after the surgical procedures, captopril was administered orally (40 mg/kg/day), while the specific Mas receptor blocker (A-779) was delivered at infusion rate of 400 ng/kg/1 min for 6 weeks. Bone metabolic markers were measured in serum and urine. Minerals concentrations were quantified in serum, urine and femoral bones by inductive coupled plasma mass spectroscopy (ICP-MS). Trabecular and cortical morphometry was analyzed in the right distal femurs using micro-CT. Finally, the expressions of RAS peptides, enzymes and receptors along with the receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) were determined femurs heads. OVX animals markedly showed altered bone metabolism and mineralization along with disturbed bone micro-structure. Captopril significantly restored the metabolic bone bio-markers and corrected Ca2+ and P values in urine and bones of estrogen deficient rats. Moreover, the trabecular and cortical morphometric features were repaired by captopril in OVX groups. Captopril also improved the expressions of ACE-2, Ang1-7, Mas and OPG, while abolished OVX-induced up-regulation of ACE-1, AngII, Ang type 1 receptor (AT1R) and RANKL. Inhibition of Ang1-7 cascade by A-779 significantly eradicated captopril protective effects on bone metabolism, mineralization and micro-structure. A-779 also restored OVX effects on RANKL expression and ACE-1/AngII/AT1R cascade and down-regulated OPG expression and ACE-2/Ang1-7/Mas pathway. In line with the clinical observations of the bone-preservative properties following ACE-1 inhibition, local activation of ACE-2/Ang1-7/Mas signaling and suppressed osteoclastogenesis seem responsible for the osteo-preservative effect of captopril, which could offers a potential therapeutic value in treatment of disabling bone and skeletal muscular diseases.

PMID:28531801 Abuohashish HM et al; Biomed Pharmacother 92: 58-68 (2017)