What is the Difference Between Cardenolides and Bufadienolides

The key difference between cardenolides and bufadienolides is that cardenolides are produced only by plants, while bufadienolides are produced by both plants and animals.

Cardenolides and bufadienolides are two chemical compounds with a steroid structure. Both are found in plants. But bufadienolides are also present in animals. Cardiac glycoside is the parent compound for both of these chemical compounds. Chemically and structurally, cardenolides and bufadienolides are aglycones, which are related to steroidal hormones. Cardenolides and bufadienolides also contain one or more sugar molecules in their structures.

CONTENTS

1. Overview and Key Difference
2. What are Cardenolides 
3. What are Bufadienolides
4. Similarities – Cardenolides and Bufadienolides
5. Cardenolides vs Bufadienolides in Tabular Form
6. Summary – Cardenolides vs Bufadienolides

What are Cardenolides?

Cardenolides are chemical compounds with a steroid structure. They are produced only by plants. Many plants contain these chemical derivatives. These chemical compounds are in the form of cardenolide glycosides. This means that they contain structural groups derived from sugars. Cardenolides are toxic to animals through the inhibition of the enzyme called Na⁺/K⁺ ATPase, which is responsible for maintaining the sodium and potassium ion gradients across the cell membrane. This can lead to heart arrests.

Cardenolides contain a 23-carbon steroid structure with methyl at carbon 10 and 13 and a 5-membered lactone at carbon 17. Members of the cardenolides group include acetyldigitoxins, acetyldigoxins, cymarine, digitoxin, digitoxigenin, digoxigenin, digoxin, medigoxin, neoconvalloside, ouabain, strophanthins, and strophanthidin. Furthermore, some plant and animal species use cardenolides in their defence mechanisms. For example, milkweed butterflies who feed on milkweeds containing cardenolides use cardenolides to deter most vertebrates’ predators. In addition, some plant species use cardenolides as a chemical defence mechanism against herbivores.

What are Bufadienolides?

Bufadienolides are chemical compounds with a steroid structure produced by both plants and animals. Bufadienolides are a group of polyhydroxy 24 carbons containing a 6-membered lactone ring at the 17-carbon position. They are mainly in the form of bufadienolide glycosides. This means they contain structural groups derived from sugars. Both Bufadienolides and their glycosides are very toxic; specifically, they can cause an atrioventricular block, bradycardia or slow heartbeat, ventricular tachycardia or rapid heartbeat, and lethal cardiac arrest.

Examples of bufadienolides include marinobufagin, proscillaridin, bufotalin, marinobufagenin, telocinobufagin and proscillaridin A. Furthermore, bufadienolides are used in Chinese medicine; they are applied topically for anesthetic effects and are used as an antiarrhythmic drug.

What are the Similarities Between Cardenolides and Bufadienolides?

• Cardenolides and bufadienolides are two chemical compounds with steroid structures.
• Both are found in plants.
• Cardiac glycoside is the parent compound for cardenolides and bufadienolides.
• Both are chemically and structurally aglycones, which are related to steroidal hormones.
• They also contain one or more sugar molecules in their structures.
• Both are toxic and can cause cardiac arrest.
• They have a wide range of uses.

What is the Difference Between Cardenolides and Bufadienolides?

Cardenolides are produced only by plants, while both plants and animals produce bufadienolides. Thus, this is the key difference between cardenolides and bufadienolides. Furthermore, the chemical formula of cardenolides is C₂₃H₃₄O_2, while the chemical formula of bufadienolides is C₂₄H₃₄O₂.

The below infographic presents the differences between cardenolides and bufadienolides in tabular form for side-by-side comparison.

Summary – Cardenolides vs Bufadienolides

Cardenolides and bufadienolides are two chemical compounds with steroid structures. They have various uses as well. Also, both these compounds are derived from a parent compound known as cardiac glycoside and are usually toxic as they cause cardiac arrest. However,  the key difference between cardenolides and bufadienolides is that cardenolides are produced only by plants while both plants and animals produce bufadienolides.

Reference:

1. Zhang, Jing, et al.“Cardenolides: Insights from Chemical Structure and Pharmacological Utility.” Pharmacological Research, U.S. National Library of Medicine.
2.“Bufadienolide.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Cardiac glucosides overview” By Amdb73 – Own work (CC0) via Commons Wikimedia
2. “Proscillaridin” By Edgar181 – Own work (CC0) via Commons Wikimedia