# Strophanthidin

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/strophanthidin
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-29
**Evidence Score:** 2 / 10
**Category:** Other
**Also Known As:** K-strophanthin, Strophanthin-K, Ouabain aglycone, 3β,5β,11α,14,19-pentahydroxycard-20(22)-enolide, Cardenolide, Strophanthidin aglycone

## Overview

Strophanthidin is a cardenolide cardiac glycoside derived from Strophanthus plants that exerts its primary effects by selectively inhibiting the Na+/K+-ATPase pump in cardiac muscle cells. This inhibition elevates intracellular sodium and calcium concentrations, producing a positive inotropic effect that strengthens myocardial contractions.

## Health Benefits

• Enhanced cardiac function in severe congestive heart failure - superior to digoxin in improving left ventricular function (RCT, PMID: 1423365)
• Improved exercise performance in advanced heart failure patients - demonstrated in 6-month trial (RCT, PMID: 8001300)
• Potential anticancer activity against lung adenocarcinoma - shown to induce apoptosis in A549 cells with IC50 of 0.51 μM (preliminary, in vitro only)
• Increased myocardial contractility through Na+/K+-ATPase inhibition - clinically observed inotropic effects
• Low cytotoxicity to normal cells - demonstrated selectivity with minimal effects on HEK293T cells at 3.02 μM (preliminary, in vitro)

## Mechanism of Action

Strophanthidin binds with high affinity to the alpha-subunit of the Na+/K+-ATPase enzyme, blocking the efflux of sodium ions from cardiomyocytes. The resulting rise in intracellular Na+ reduces activity of the Na+/Ca2+ exchanger, causing calcium accumulation within the sarcoplasmic reticulum and increasing the force of myocardial contraction. Additionally, strophanthidin modulates downstream signaling cascades including Src kinase and EGFR transactivation pathways, which may contribute to both its cardiac effects and its observed antiproliferative activity in cancer cell lines.

## Clinical Summary

A randomized controlled trial (PMID: 1423365) demonstrated that strophanthidin produced superior improvements in left ventricular ejection fraction compared to digoxin in patients with severe congestive heart failure, establishing a clinically meaningful advantage over the standard-of-care cardiac glycoside. A separate 6-month RCT (PMID: 8001300) documented measurable gains in exercise performance in advanced heart failure patients receiving strophanthidin. Emerging in vitro and preclinical data suggest anticancer activity, though human clinical trial evidence for oncological applications remains absent. Overall, cardiac evidence is limited to small RCTs, and large-scale, long-term safety and efficacy trials in modern populations are lacking.

## Nutritional Profile

Strophanthidin is not a nutrient or food substance; it is a cardenolide-type cardiac glycoside (aglycone) with the molecular formula C₂₃H₃₂O₆ and molecular weight of 404.50 g/mol. It contains no macronutrients (protein, carbohydrates, fat), fiber, vitamins, or minerals. Key bioactive characteristics: • Primary bioactive compound: Strophanthidin itself — a steroidal aglycone derived from hydrolysis of k-strophanthoside and other Strophanthus glycosides (e.g., cymarin, convallatoxin). • Source organisms: Seeds of Strophanthus kombe, Strophanthus gratus, and related Apocynaceae species; also found in Convallaria majalis (lily of the valley). • Structural features: 5β,14β-androstane skeleton with a β-unsaturated γ-butyrolactone ring (C-17), hydroxyl groups at C-3β, C-5β, and C-14β, and an aldehyde group at C-10 (distinguishing it from other cardenolides like digitoxigenin). • Mechanism of action: Potent inhibitor of Na⁺/K⁺-ATPase (sodium-potassium pump) with IC₅₀ values in the nanomolar to low micromolar range depending on isoform; binds to the α-subunit extracellular domain. • Pharmacologically active concentration range: Cardiac glycoside activity observed at ~10⁻⁸ to 10⁻⁶ M; anticancer IC₅₀ reported at ~0.51 μM in A549 cells. • Bioavailability notes: As an aglycone (sugar-free form), strophanthidin has relatively higher lipophilicity and oral absorption compared to its parent glycosides (e.g., ouabain/g-strophanthin), though oral bioavailability remains limited and variable. Historically administered parenterally. Hepatic [metabolism](/ingredients/condition/weight-management) is significant; plasma half-life is relatively short compared to digoxin. • Therapeutic index: Extremely narrow — the toxic dose is close to the therapeutic dose, consistent with all cardiac glycosides. Not classified as a dietary supplement or nutritional compound. Exclusively used as a pharmaceutical/research agent.

## Dosage & Preparation

Clinical trials used intravenous K-strophanthidin administered daily in 10ml saline, though specific milligram doses were not reported in available abstracts. Anticancer in vitro studies used concentrations of 0.51 μM for 48-hour treatments. No standardized oral dosing or extract preparations have been established. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Strophanthidin carries a narrow therapeutic index similar to other cardiac glycosides, with toxicity manifesting as bradycardia, heart block, ventricular arrhythmias, nausea, and visual disturbances at supratherapeutic exposures. Co-administration with antiarrhythmics such as amiodarone, calcium channel blockers, or other Na+/K+-ATPase inhibitors like digoxin significantly increases risk of additive cardiotoxicity and is contraindicated without close monitoring. Hypokalemia, hypomagnesemia, and hypercalcemia potentiate strophanthidin toxicity by sensitizing the Na+/K+-ATPase to inhibition, requiring electrolyte monitoring during use. Safety in pregnancy and lactation has not been established in controlled human studies, and strophanthidin should be avoided in these populations absent compelling clinical necessity.

## Scientific Research

Two key clinical trials examined strophanthidin in heart failure: a double-blind crossover RCT (PMID: 1423365) in 20 patients showed K-strophanthidin superior to digoxin for left ventricular function, and a 6-month trial (PMID: 8001300) in 22 patients demonstrated improved pump function. Anticancer evidence remains preclinical, limited to in vitro studies on lung, breast, and liver cancer cell lines.

## Historical & Cultural Context

Strophanthidin originates from traditional Chinese medicine, where plants like Semen Lepidii and Antiaris toxicaria have been used for heart failure treatment. Its use parallels the historical application of cardiac glycosides like digitalis, with K-strophanthin forms being employed clinically for congestive heart failure management.

## Synergistic Combinations

Hawthorn extract, CoQ10, L-carnitine, magnesium, taurine

## Frequently Asked Questions

### How does strophanthidin differ from digoxin in treating heart failure?

A published RCT (PMID: 1423365) found strophanthidin produced greater improvements in left ventricular function compared to digoxin in severe congestive heart failure patients, suggesting a superior inotropic profile. Strophanthidin binds the Na+/K+-ATPase alpha-subunit with somewhat different affinity kinetics than digoxin, which may account for pharmacodynamic differences. However, digoxin has decades more safety and pharmacokinetic data in humans, making it the clinically preferred choice outside of investigational settings.

### What is the mechanism by which strophanthidin inhibits cancer cell growth?

Strophanthidin inhibits Na+/K+-ATPase on cancer cell membranes, disrupting ionic homeostasis and triggering downstream apoptotic signaling pathways including activation of caspase-3 and suppression of Bcl-2 expression. It also appears to interfere with HIF-1alpha-mediated hypoxia signaling, which cancer cells rely on for survival in low-oxygen tumor microenvironments. These findings are currently derived from in vitro and animal studies, with no completed human clinical trials confirming anticancer efficacy.

### What are the symptoms of strophanthidin toxicity?

Early signs of strophanthidin toxicity include nausea, vomiting, anorexia, and fatigue, mirroring the classic toxidrome of cardiac glycoside poisoning. Cardiac manifestations include bradycardia, first- through third-degree atrioventricular block, and potentially life-threatening ventricular arrhythmias such as ventricular fibrillation. Visual disturbances including yellow-green color halos around lights are a hallmark neurological sign of glycoside toxicity and warrant immediate dose reassessment.

### Can strophanthidin be taken with diuretics?

Loop diuretics such as furosemide and thiazide diuretics can induce hypokalemia and hypomagnesemia, both of which potentiate strophanthidin's inhibition of Na+/K+-ATPase and increase arrhythmia risk. If concurrent use is medically necessary, serum potassium levels should be maintained above 3.5 mEq/L and magnesium above 0.8 mmol/L through supplementation or dietary adjustment. Potassium-sparing diuretics like spironolactone carry lower risk of this interaction and are sometimes preferred in cardiac failure management alongside glycosides.

### What plant sources does strophanthidin come from?

Strophanthidin is the aglycone (sugar-free core) of several naturally occurring cardiac glycosides found primarily in plants of the genus Strophanthus, including Strophanthus gratus and Strophanthus kombé, native to tropical Africa. It is also found in Convallaria majalis (lily of the valley) as a minor glycoside component. In its naturally occurring plant form, strophanthidin is bound to sugar moieties forming glycosides such as ouabain (g-strophanthin), which are hydrolyzed to free strophanthidin upon metabolic processing.

### What does clinical research show about strophanthidin's effectiveness in heart failure compared to standard treatments?

Clinical trials demonstrate that strophanthidin produces superior improvements in left ventricular function compared to digoxin in severe congestive heart failure, with one RCT (PMID: 1423365) showing enhanced cardiac outcomes. A 6-month randomized controlled trial (PMID: 8001300) documented improved exercise performance in advanced heart failure patients receiving strophanthidin. While these results are promising, strophanthidin remains less widely studied than conventional cardiac medications, and more modern comparative trials are needed to establish its role in contemporary heart failure management.

### Is strophanthidin safe for elderly patients with heart conditions?

Strophanthidin requires careful medical supervision in elderly patients due to the narrow therapeutic window of cardiac glycosides and increased risk of toxicity with age-related changes in kidney function and drug metabolism. Elderly individuals are particularly vulnerable to strophanthidin's cardiac and gastrointestinal side effects, necessitating lower doses and frequent monitoring of serum levels and ECG parameters. This ingredient should only be used in elderly patients under strict cardiology supervision with baseline renal function assessment.

### What is the most bioavailable form of strophanthidin, and does food affect its absorption?

Strophanthidin is a cardiac glycoside with variable oral bioavailability that can be affected by gastrointestinal pH, motility, and the presence of food or fiber, which may reduce absorption. The intravenous form provides the most predictable bioavailability and is often preferred in acute clinical settings, though oral formulations have historically been used for chronic heart failure management. Individual absorption varies significantly based on gut flora composition and gastrointestinal disease status, making therapeutic drug monitoring essential for optimal dosing.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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