Notes on bufadienolides
A working site for what I read, measure and get wrong while studying bufadienolides. Updates are slow and corrections are slower, but every entry tries to state its evidence and its limits.
Why this topic
Bufadienolides are steroidal compounds carrying a 2-pyrone ring at C-24, found widely in traditional materials such as toad venom. Their structural diversity comes mostly from hydroxylation, epoxidation and substitution on the steroidal core, and most of these modifications are carried out by cytochrome P450 enzymes.
Two things make this field interesting. First, the same core can follow completely different modification routes across species and tissues, producing products with very different activity. Second, these enzymes are often promiscuous and produce mixtures, which makes conventional in vitro screening poor at separating them. So the question I care about is not "which enzyme can catalyse this step" but "which route will this enzyme prefer in a real system".
Many reported P450 modification sites were measured with pure enzyme and excess substrate.
Those results show what the enzyme can do, not what it does inside a cell. Read the system conditions first.
Recent note
- Reading a paper on P450 modification of bufadienolides
Literature note · 2026-10-27 · in Chinese
Ongoing interests
- Site selectivity on the steroidal core: how one P450 prefers one position over another, and whether that preference can be explained structurally.
- Enzyme assays and quantification: separating target products from side products in messy mixtures, and producing numbers that hold up.
- Common pitfalls in natural product enzymology: substrate solubility, nonspecific binding, false positive activity, and how these are actually handled.
Contact
Email: stern@stern612.com
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