Most people who follow cannabinoid science are familiar with the big names: CBD, THC, CBG, CBN. But the cannabis plant contains well over 100 distinct cannabinoids, and analytical chemistry keeps turning up new ones that were previously too minor to characterize cleanly.
CBD-C4 — also known as cannabidibutol (CBDB) — is one of the more recently identified members of this group. It was formally characterized for the first time only in 2019, discovered not through a dedicated hunt for new cannabinoids, but as an impurity in commercial CBD extract. What’s been learned since is genuinely interesting, even if the full picture is still taking shape.
What Is CBD-C4?
CBD-C4 is the informal name for cannabidiol-C4, a naturally occurring minor phytocannabinoid in the cannabis plant. Its formal chemical name is cannabidibutol (CBDB), and it carries the CAS number 60113-11-3. The molecular formula is C₂₀H₂₈O₂, with a molecular weight of 300.44 g/mol (Citti et al., 2019).
Structurally, CBD-C4 is a homolog of CBD — sharing the same terpenophenolic backbone — with one key difference: where CBD has a five-carbon (pentyl) side chain on its resorcinol ring, CBD-C4 has a four-carbon (butyl) chain. That single carbon difference earns it the “C4” designation.
CAS Number: 60113-11-3
Molecular Formula: C₂₀H₂₈O₂ / Molecular Weight: 300.44 g/mol
Parent compound: Cannabidiol (CBD)
Classification: Minor phytocannabinoid / CBD homolog
Psychoactive: No evidence of psychoactivity
How Was It Discovered?
CBD-C4 wasn’t discovered in a targeted search for new cannabinoids — it turned up while researchers were doing routine quality analysis on commercial CBD. Citti et al. (2019) identified two consistent impurities in hemp-derived CBD extract: the already-known cannabidivarin (CBDV) and a second unknown compound with a four-carbon side chain.
That second compound was CBD-C4. The team isolated it via semi-preparative liquid chromatography, then subjected it to comprehensive spectroscopic characterization — including NMR, UV, IR, circular dichroism, and high-resolution mass spectrometry — to confirm its structure and absolute configuration. To verify their findings, they also performed a stereoselective synthesis and confirmed a perfect match between the natural isolate and the synthetic compound (Citti et al., 2019).
CBD-C4 vs. CBD: What’s the Difference?
The two compounds are structurally nearly identical, but the one-carbon difference in side chain length has real consequences. Alkyl side chain length is one of the primary pharmacophoric determinants in cannabinoid chemistry — it influences receptor binding affinity, lipophilicity, and how the body absorbs and metabolizes the compound (Linciano et al., 2019).
| Property | CBD | CBD-C4 (CBDB) |
|---|---|---|
| Alkyl side chain | n-pentyl (C5) | n-butyl (C4) |
| CAS Number | 13956-29-1 | 60113-11-3 |
| Lipophilicity | Moderate | Lower than CBD |
| Natural abundance | Major cannabinoid | Trace (0.16–0.26% w/w in CBD) |
| Psychoactivity | None | None reported |
| First characterized | 1963 | 2019 |
| Consumer availability | Widely available | Research use only |
Because CBD-C4 is less lipophilic than CBD, it’s expected to differ in how it’s absorbed, distributed through the body, and eliminated — though no dedicated pharmacokinetic studies have been published yet (Salbini et al., 2021).
Natural Occurrence & Concentration
CBD-C4 exists in cannabis in genuinely trace amounts. Analysis of ten batches of commercially produced, GMP-compliant hemp-derived CBD showed CBDB concentrations consistently between 0.16 and 0.26% w/w, with a mean of approximately 0.20%. In highly purified CBD preparations, residual CBD-C4 typically doesn’t exceed 0.50% w/w (GW Pharmaceuticals, 2018, as cited in GB2579179A).
Beyond hemp-derived CBD, CBD-C4 has also been detected in the Italian medicinal cannabis variety FM2 (Linciano et al., 2019). Its consistent presence across diverse cannabis sources suggests it’s a genuine minor constituent of the plant rather than a synthesis artifact or processing contaminant.
Because it co-elutes with structurally similar compounds and occurs at such low concentrations, isolating pure CBD-C4 directly from plant material in useful quantities is not practically feasible. This is why synthetic production is the primary route for obtaining reference-grade material for research (Marzullo et al., 2022).
Where Does It Come From in the Plant?
This is one of the more interesting open questions around CBD-C4. No plant enzymes specifically responsible for producing butyl-chain cannabinoids have been identified to date. The leading hypothesis is that CBD-C4 and its THC-family counterpart (Δ9-tetrahydrocannabutol, or Δ9-THCB) are produced not by direct plant biosynthesis, but through microbial ω-oxidation and decarboxylation of their five-carbon homologs (Linciano et al., 2019).
In other words, bacteria or fungi associated with the cannabis plant may be transforming CBD into CBD-C4 as a secondary metabolic process. This is consistent with biotransformation pathways previously documented in fungi such as Syncephalastrum racemosum (Linciano et al., 2019). The practical implication is that CBD-C4 content in cannabis products may vary depending on microbial conditions during cultivation, harvest, and processing — though this has not yet been systematically studied.
What Does the Research Say?
Anticancer Activity in Breast Cancer Cells
The most substantive pharmacological data on CBD-C4 published to date comes from Salbini et al. (2021), who investigated the effects of CBDB alongside another novel cannabinoid, CBDP (cannabidiphorol), in human breast carcinoma cell lines that express cannabinoid receptors.
The results showed that CBDB affected cell viability, increased intracellular production of reactive oxygen species (ROS), and activated cellular signaling pathways associated with ROS-mediated stress — effects that paralleled those already documented for natural and synthetic CBD (Salbini et al., 2021).
What made the findings particularly notable was the potentiation effect: when CBDB was combined with a monoacylglycerol lipase (MAGL) inhibitor (an enzyme involved in endocannabinoid metabolism) or with phorbol ester 12-myristate 13-acetate (PMA, an activator of protein kinase C), biological activity was significantly amplified (Salbini et al., 2021). This suggests that CBD-C4 may work synergistically with agents that modulate endocannabinoid metabolism or intracellular stress pathways.
Receptor Profile
Formal receptor binding data for CBD-C4 at cannabinoid (CB1/CB2) or non-cannabinoid receptors have not been published. Based on structure-activity relationship principles — specifically that minimum three carbons are required for cannabinoid receptor binding, with peak activity around eight carbons — CBD-C4’s four-carbon chain places it in the functional range, but with likely weaker receptor affinity than longer-chain homologs (Linciano et al., 2019).
Synthesis Research
Marzullo et al. (2022) published a total enantioselective synthesis of CBD-C4, employing a five-step route that included a Corey-Bakshi-Shibata reduction, Claisen-Ireland rearrangement, ring-closing metathesis, and demethylation via sodium ethanethiolate. This synthesis work is significant because it enables production of chemically defined, stereoisomerically pure CBD-C4 for pharmacological investigation — something plant extraction cannot reliably provide.
Is CBD-C4 Available as a Supplement?
No. At the time of writing, CBD-C4 is not available as a consumer supplement. It is sold exclusively as an analytical reference standard for laboratory use, at milligram quantities and ≥98% purity (Cayman Chemical, n.d.).
That said, patent activity suggests commercial interest in the compound beyond its role as an impurity marker. Patent applications have been filed in both the UK (GB2579179A) and Brazil (BR112021009815A2) relating to CBD-C4’s use as a medicine, with data described demonstrating efficacy in disease models. Whether this translates to a consumer or pharmaceutical product will depend on the progression of clinical research.
Frequently Asked Questions About CBD-C4
Is CBD-C4 the same as CBDB?
Yes. CBD-C4, CBDB, and cannabidibutol are all names for the same compound (CAS 60113-11-3). “CBD-C4” refers to the four-carbon side chain, “CBDB” uses the “B” for butyl, and cannabidibutol is the formal International Nonproprietary Name suggested by Citti et al. (2019).
Is CBD-C4 psychoactive?
There is no evidence that CBD-C4 is psychoactive. Like CBD itself, it is not expected to activate CB1 receptors in the manner that produces intoxication. Its four-carbon side chain is actually shorter than CBD’s, which generally correlates with lower receptor affinity (Linciano et al., 2019).
Does CBD-C4 occur naturally in cannabis?
Yes, but only in trace amounts. It has been detected in hemp-derived CBD extracts at 0.16–0.26% w/w, and in the Italian medicinal cannabis variety FM2 (Citti et al., 2019; Linciano et al., 2019). Its biosynthetic origin is not fully established.
Is CBD-C4 legal?
CBD-C4 is not a federally scheduled substance in the United States, and it does not appear on international controlled substance lists at the time of writing. However, cannabinoid regulations vary by jurisdiction and are subject to change. It is currently available only as a research reference standard.
How does CBD-C4 differ from CBDV?
Both are CBD homologs with shorter side chains, and both appear as impurities in hemp-derived CBD. CBDV has a three-carbon (propyl) chain, making it the C3 homolog, while CBD-C4 has a four-carbon (butyl) chain. CBDV has been studied far more extensively, including in human clinical trials for epilepsy (Citti et al., 2019).
The Bottom Line
CBD-C4 (cannabidibutol/CBDB) is one of the newer additions to the growing roster of characterized phytocannabinoids. Discovered only in 2019 as a trace impurity in commercial CBD extract, it’s a close structural relative of CBD — just one carbon shorter on its alkyl side chain.
What little research exists points to biological activity consistent with the CBD family: ROS induction, effects on cell viability in cancer cell lines, and apparent synergy with endocannabinoid-modulating agents. But the evidence base is thin — a single in vitro study, some synthesis work, and a pair of patent filings. Receptor binding data, animal studies, and anything resembling human clinical evidence are all absent.
For now, CBD-C4 is a compound for researchers and cannabinoid enthusiasts to watch — a reminder that the cannabis plant’s chemistry is still being mapped, and that the most interesting discoveries sometimes come from looking closely at what we thought was background noise.
Nothing in this article constitutes medical advice. Always consult a qualified healthcare provider before making decisions about supplementation or treatment.
