Pivalopril (RHC 3659-(S); (S)-N-cyclopentyl-N-(2-methyl-3-pivaloylthiopropionyl) glycine) is an angiotensin-converting enzyme (ACE) inhibitor with antihypertensive activity. Upon hydrolysis, the free SH metabolite of pivopril competitively binds to and inhibits ACE, thereby blocking the conversion of angiotensin I to angiotensin II. This prevents the potent vasoconstrictive actions of angiotensin II and results in vasodilation. Pivopril also decreases angiotensin II-induced aldosterone secretion by the adrenal cortex, which leads to an increase in sodium excretion and subsequently increases water outflow. Pivalopril has been compared to captopril for oral angiotensin-converting enzyme (ACE) inhibition in rats and dogs and antihypertensive activity in rats. In separate groups of conscious normotensive rats, pivalopril (0.03-1.0 mg/kg, orally [p.o.]) produced a dose-related antagonism of angiotensin I (AngI)-induced pressor effects. The ED50 for pivalopriland captopril was 0.1 mg/kg. Pivalopril has being shown to be a potent, orally effective ACE inhibitor and antihypertensive agent.

CAPOZIDE (captopril and hydrochlorothiazide tablets, USP) for oral administration combines two antihypertensive agents: captopril and hydrochlorothiazide. The mechanism of action of captopril has not yet been fully elucidated. Captopril prevents the conversion of angiotensin I to angiotensin II by inhibition of ACE, a peptidyldipeptide carboxy hydrolase. Hydrochlorothiazide belongs to thiazide class of diuretics. It reduces blood volume by acting on the kidneys to reduce sodium (Na+) reabsorption in the distal convoluted tubule. CAPOZIDE (captopril and hydrochlorothiazide tablets, USP) is indicated for the treatment of hypertension. The blood pressure lowering effects of captopril and thiazides are approximately additive. Major side effects are: Black, tarry stools; chest pain; chills; cough; fever; painful or difficult urination; shortness of breath; sore throat; sores, ulcers, or white spots on lips or in mouth; swollen glands; unusual bleeding or bruising; unusual tiredness or weakness. It has been reported that indomethacin may reduce the antihypertensive effect of captopril, especially in cases of low renin hypertension. Captopril’s effect will be augmented by antihypertensive agents that cause renin release. For example, diuretics (e.g., thiazides) may activate the renin-angiotensin-aldosterone system.

Ecadotril or sinorphan is the S-enantiomer of racemic acetorphan (racecadotril). It inhibits enkephalinase activity. Ecadotril was studied for the treatment of hypertension and heart failure, however, its development was discontinued.

Fasidotril is a diester prodrug of the active metabolite fasidotrilat. Fasidotrilat inhibited both angiotensin I converting enzyme (ACE, EC 3.4.25.1) and neprilysin (NEP, EC 3.4.24.11, also named neutral endopeptidase, enkephalinase, or atriopeptidase) at nanomolar concentrations (Ki = 9.8 nM against ACE and 5.1 nM against NEP) Fasidotril was being developed for the treatment of myocardial infarction, congestive heart failure and myocardial infarction.

Secoisolariciresinol diglucoside (SDG) isolated from flaxseed is a lipid-lowering and antioxidant agent. It suppresses the development of hypercholesterolemic atherosclerosis in rabbits. Secoisolariciresinol diglucoside has been shown to have antioxidant and cardioprotective properties. SDG interferes with the development of different types of diseases like cardiovascular, diabetic, lupus nephritis, bone, kidney, menopause, reproduction, mental stress, immunity, atherosclerosis, hemopoietic, liver necrosis and urinary disorders due to its various biological properties including anti-inflammatory, antioxidant, antimutagenic, antimicrobial, antiobesity, antihypolipidemic and neuroprotective effects. Moreover, SDG has a defending mediator against various cancers by modulating multiple cell signaling pathways. The animal and human studies have shown the prevention role of SDG against some cancers (breast, lung and colon) as a result of its strong anti-proliferative, antioxidant, anti-oestrogenic and/or anti-angiogenic activity. It is proposed that the anticancer activity of SDG is associated with the inhibition of enzymes involved in carcinogenesis. Human studies showed the SDG as potential cardiovascular protector by mediating the mechanisms of total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerides and glucose metabolism. It was observed that 20 hypercholesterolaemia and hypertriglyceridaemia subjects receiving 600 mg SDG per day for 8 weeks led to significant reductions in total cholesterol, LDL-cholesterol and glucose concentrations compared with the placebo group. The animal and human studies revealed that high fat diet containing 0 · 5 to 1 · 0 % SDG reduces liver triglycerides content, serum triglycerides, total cholesterol, and insulin and leptin concentrations that resulted in significantly reduced visceral fat gain as compared to group of mice receiving high fat diet without SDG. SDG reduces C-reactive protein concentrations which are associated with insulin resistance and diabetes mellitus in type 2 diabetics. Daily consumption of low-fat muffin enriched with SDG (500 mg/day) for 6 week can reduce CRP concentrations. SDG has long acting hypotensive effect mediated through the guanylate cyclase enzyme.

Indolapril (CI-907) is a new orally active prodrug of nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor, developed by Warner-Lambert/Parke-Davis Pharmaceutical Research for treating hypertension. Indolapril is epimer of trandolapril, well-known ACE inhibitor currently in the market for hypertension treatment. Indolapril (Monoester form) and it’s active component (diacid form) produced concentration related ACE inhibition in guinea-pig serum (IC50 for monoester -- 0.1 mkM and for diacid -- 2.6 nM). In isolated rabbit aortic rings and in rat and dog autonomic studies, Indolapril is highly specific in suppressing the contractile or pressor responses to angiotensin I. In two-kidney, one-clip Goldblatt hypertensive rats, single daily doses (0.03-30 mg/kg p.o.) produced dose-dependent decreases in blood pressure; 3 mg/kg lowered blood pressure to normotensive levels. In the spontaneously hypertensive rat, subacute administration of Indolapril produced the same decrease in blood pressure as that obtained in the renal hypertensive rat. In diuretic-pretreated renal hypertensive dogs, 10 mg/kg normalized blood pressure. For equivalent drops in blood pressure, heart rate increases were less in Indolapril than in enalapril-treated renal hypertensive dogs. No side effects were observed with CI-907 in any of the conscious animals. The antihypertensive response to Indolapril (0.03-1.0 mg/kg p.o.) was found to correlate with inhibition of vascular tissue ACE, but not plasma or brain ACE in two-kidney, one-clip renal hypertensive rats.

Teprotide, a nonapeptide isolated from the venom of a Brazilian pit viper, Bothrops jararaca, was the first angiotensin converting enzyme (ACE) inhibitor to be discovered and tested. It was found to be an effective, non-toxic antihypertensive agent as well as an afterload-reducing agent for patients with congestive heart failure (CHF). The primary activity of teprotide resulted from blockade of the angiotensin I converting enzyme--the pivotal step in the renin-angiotensin-aldosterone system (RAAS), and consequent reductions in angiotensin II levels. There was limited clinical testing for teprotide because of: its scarcity; the need for parenteral administration; and the subsequent discovery and synthesis of captopril, the first orally active angiotensin converting enzyme inhibitor.

Nicotine-1'-N-oxide (NNO) is an oxidation product of nicotine. Flavin-containing monooxygenase is responsible for the oxygen transfer. Nicotine N'- oxide is a primary metabolite of nicotine, although only about 4-7% of nicotine absorbed by smokers is metabolized via this route. It appears that NNO is not further metabolized to any significant extent, except by reduction back to nicotine, which may lead to recycling of nicotine in the body.