# Rhamnose
**Rhamnose** is a 6-deoxy hexose sugar, specifically 6-deoxy-L-mannose, a methylpentose with the molecular formula C₆H₁₂O₅ whose L-isomer occurs naturally in many plant glycosides and in some gram-negative bacterial lipopolysaccharides.[1](https://www.ncbi.nlm.nih.gov/mesh/68012210) It is widely distributed in bacteria and plants but rare in animals, a distribution that underlies both its role as a building block of plant cell walls and its value as a target in antibacterial research.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934) • [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9415975/)
| Key fact | Detail |
|---|---|
| Identity | 6-Deoxy-L-mannose (methylpentose); IUPAC name 6-deoxy-L-manno-hexopyranose; PubChem CID 25310[4](https://pubchem.ncbi.nlm.nih.gov/compound/L-Rhamnose) |
| Formula and mass | C₆H₁₂O₅; molecular weight 164.16 g/mol; melting point 122 °C; CAS Registry Number 3615-41-6[4](https://pubchem.ncbi.nlm.nih.gov/compound/L-Rhamnose) • [5](https://webbook.nist.gov/cgi/cbook.cgi?ID=C3615416) |
| Natural occurrence | Plant glycosides, gram-negative bacterial lipopolysaccharides, plant cell wall pectins, and bacterial capsular polysaccharides[1](https://www.ncbi.nlm.nih.gov/mesh/68012210) • [6](https://www.preprints.org/manuscript/202603.1063/v1/download) |
| Activated donor forms | dTDP-Rha and GDP-Rha in bacteria and fungi; UDP-Rha in plants[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9415975/) |
| Bacterial catabolism | Many bacteria, including Enterobacteriaceae and Rhizobiaceae, use L-rhamnose as a carbon source; E. coli imports it through the RhaT permease[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3870299/) |
| Industrial relevance | Sugar moiety of rhamnolipid biosurfactants; removed by naringinase to debitter citrus juices and increase flavonoid bioavailability[8](https://www.sciencedirect.com/science/article/pii/S0308814626027640) • [9](https://www.mdpi.com/1420-3049/30/11/2376) |
## Chemical identity
Rhamnose is a hexose that lacks the hydroxyl group at carbon 6, which is replaced by a hydrogen and makes it a 6-deoxy sugar; the methyl group at that position is why it is also classed as a methylpentose.[1](https://www.ncbi.nlm.nih.gov/mesh/68012210) In its common cyclic form it is L-rhamnopyranose, the enantiomer of D-rhamnopyranose.[4](https://pubchem.ncbi.nlm.nih.gov/compound/L-Rhamnose) NIST lists synonyms including isodulcit, isodulcitol, locaose, and L-mannomethylose.[5](https://webbook.nist.gov/cgi/cbook.cgi?ID=C3615416) Computed properties reflect a small, highly hydrophilic molecule: XLogP of −2.1, four hydrogen bond donors, five acceptors, and no rotatable bonds.[4](https://pubchem.ncbi.nlm.nih.gov/compound/L-Rhamnose)
## Occurrence in plants
**Cell wall polysaccharides** hold most of the rhamnose in plants. In [Arabidopsis](https://www.edgepedia.org/arabidopsis) leaves, about 682 μg per gram fresh weight, roughly 90 percent of the total rhamnose, is incorporated into cell wall matrix polysaccharides, with smaller amounts in soluble specialized metabolites and water-soluble polymers such as arabinogalactan proteins.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934) The principal destination is the pectin domain rhamnogalacturonan I (RG-I), whose backbone is the repeating disaccharide (1,4)-α-GalA-(1,2)-α-Rha, alternating galacturonic acid and rhamnose residues that anchor arabinan, galactan, and arabinogalactan side chains.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934) • [10](https://doi.org/10.1146/annurev-arplant-081519-035846) Rhamnose also appears in rhamnogalacturonan II, a highly conserved pectic domain containing more than 20 linkages on 12 different sugars.[11](https://onlinelibrary.wiley.com/doi/10.1111/jipb.13055)
The distribution differs by plant lineage: rhamnose accumulation in the cell walls of grasses (commelinid monocotyledons) is significantly smaller than in dicotyledonous plants, consistent with the lower pectin content of grass walls.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934) • [12](https://www.sciencedirect.com/science/article/pii/S0008621509002006) Rhamnose is also conjugated to specialized metabolites, including flavonoids such as the C-glycosylflavone violanthin, in which the sugar is attached through a carbon-carbon bond that is more stable and resistant to acid hydrolysis than the usual ether linkage.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934)
## Biosynthesis
Cells attach rhamnose to acceptor molecules through rhamnosyltransferases that use nucleotide-sugar donors. Three donors are known: deoxythymidinediphosphate-L-rhamnose (dTDP-Rha), guanosine diphosphate rhamnose (GDP-Rha), and uridine diphosphate-rhamnose (UDP-Rha). dTDP-Rha and GDP-Rha occur in bacteria and fungi, whereas UDP-Rha is found only in plants.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9415975/)
**The bacterial dTDP-Rha pathway** is the most studied. Four enzymes convert D-glucose-1-phosphate to dTDP-L-rhamnose: glucose-1-phosphate thymidylyltransferase (RmlA), dTDP-D-glucose 4,6-dehydratase (RmlB), dTDP-4-keto-6-deoxy-D-glucose 3,5-epimerase (RmlC), and dTDP-4-keto-L-Rha reductase (RmlD).[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9415975/) In *Pseudomonas aeruginosa*, this pathway supplies the hydrophilic moiety of rhamnolipids, and coexpression of the rmlBDAC operon is used to raise rhamnolipid titers in engineered production strains.[8](https://www.sciencedirect.com/science/article/pii/S0308814626027640) • [13](https://pmc.ncbi.nlm.nih.gov/articles/PMC7642724/)
**The plant UDP-Rha pathway** starts from [UDP-glucose](https://www.edgepedia.org/udp-glucose) and is catalyzed by multifunctional rhamnose synthases (RHM). The RHM enzyme carries an N-terminal UDP-Glc 4,6-dehydratase domain that forms the intermediate UDP-4-keto-6-deoxy-D-glucose, and a C-terminal domain with dual 3,5-epimerase and 4-keto-reductase activities that complete the conversion to UDP-Rha.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934) Rhamnosyltransferases then transfer the rhamnose residue from UDP-Rha onto a large variety of substrates in primary and specialized metabolism.[2](https://www.sciencedirect.com/science/article/pii/S0168945220302934)
## Catabolism in microorganisms
Many microorganisms can degrade rhamnose-containing polymers and use the released sugar. Plant-pathogenic *Erwinia* species and saprophytes such as *Bacillus subtilis* break down rhamnogalacturonans with extracellular enzymes including rhamnogalacturonate lyases and α-L-rhamnosidases; the liberated L-rhamnose then enters the cell through specific transporters such as the RhaT permease of [Enterobacteriaceae](https://www.edgepedia.org/enterobacteriaceae).[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3870299/) A comparative genomics survey across six bacterial phyla reconstructed the catabolic pathways and found substantial variation in the transcriptional regulators controlling them, including a novel bifunctional aldolase-dehydrogenase enzyme in [Chloroflexi](https://www.edgepedia.org/chloroflexi), Bacilli, and [Alphaproteobacteria](https://www.edgepedia.org/alphaproteobacteria).[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3870299/) An alternative nonphosphorylated pathway, converting L-rhamnose to pyruvate and L-lactaldehyde in four steps, has been identified in fungi and in the bacteria *Azotobacter vinelandii* and *Sphingomonas* sp.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3870299/)
## Industrial and medical relevance
**Rhamnolipids** are bacterial biosurfactants in which one rhamnose ring (mono-rhamnolipids) or two (di-rhamnolipids) form the polar head, linked to β-hydroxy fatty acid chains. They are valued for surface activity, rapid biodegradability, and antimicrobial and antitumor bioactivities, with applications explored in oil recovery, cosmetics, food science, agriculture, and drug delivery; low yield and high production cost currently limit industrial use.[8](https://www.sciencedirect.com/science/article/pii/S0308814626027640) • [14](https://www.sciencedirect.com/science/article/pii/S135902942300105X) Rhamnolipids themselves serve as a source of L-rhamnose, which can be released by enzymatic hydrolysis as a raw material for flavor compounds.[15](https://pmc.ncbi.nlm.nih.gov/articles/PMC5544971/)
**Food processing** exploits enzymes that cleave rhamnosidic bonds. Naringinase, a complex of α-L-rhamnosidase and β-D-glucosidase, removes the rhamnose moiety from bitter flavonoid glycosides such as naringin in citrus juice; when rhamnose is removed from such glycosides the bitter taste is lost, and the resulting products show increased water solubility and bioavailability.[9](https://www.mdpi.com/1420-3049/30/11/2376) • [16](https://revistas.elpoli.edu.co/index.php/pol/article/download/2408/2384/15935) α-L-Rhamnosidases are also applied to enhance the aroma of wine and fruit juices.[17](https://www.sciencedirect.com/topics/chemistry/l-rhamnose)
**Medicine** takes advantage of the taxonomic distribution of the sugar. Because rhamnose-containing molecules are present in bacteria but not mammals, their biosynthetic enzymes are studied as potential antibacterial targets, and rhamnose-associated compounds are also being investigated for tumor immunotherapy.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9415975/) In bacterial cell walls and capsular polysaccharides, rhamnose contributes to structural integrity and to immunological properties by influencing host-pathogen interactions.[6](https://www.preprints.org/manuscript/202603.1063/v1/download)
## Commercial production
Commercial L-rhamnose was historically extracted from plant glycosides such as those of oak bark and citrus fruits. Current production relies on extraction from rhamnose-rich starting materials, including purified glycosides such as rutin and naringin, crude citrus material from unripe fruit or peel waste, gum arabic, and microbial rhamnolipids or rhamnopolysaccharides such as polyrhamnose.[18](https://wellkr.com/how-is-rhamnose-produced-commercially) • [19](https://patents.google.com/patent/US5077206) Citrus peel, generated in large quantities by the juice industry, is a particularly practical feedstock because its flavonoid glycosides carry rhamnose in a terminal position that hydrolysis releases.[19](https://patents.google.com/patent/US5077206)
## References
1. [Rhamnose, Medical Subject Headings, NCBI](https://www.ncbi.nlm.nih.gov/mesh/68012210)
2. [Jiang, N. et al. (2021). Rhamnose in plants – from biosynthesis to diverse functions. Plant Science 302, 110687.](https://www.sciencedirect.com/science/article/pii/S0168945220302934)
3. [Rhamnose-Containing Compounds: Biosynthesis and Applications (2022), PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC9415975/)
4. [L-Rhamnose, CID 25310, PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/L-Rhamnose)
5. [Rhamnose, NIST Chemistry WebBook, SRD 69](https://webbook.nist.gov/cgi/cbook.cgi?ID=C3615416)
6. [Rhamnose (preprint section), Preprints.org](https://www.preprints.org/manuscript/202603.1063/v1/download)
7. [Comparative genomics and functional analysis of rhamnose catabolic pathways and regulons in bacteria, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3870299/)
8. [Pang, A.-P. et al. (2026). Rhamnolipids: from biosynthesis to applications. Food Chemistry 525.](https://www.sciencedirect.com/science/article/pii/S0308814626027640)
9. [Use of Naringinase to Modify the Sensory Quality of Foods and Increase the Bioavailability of Flavonoids: A Systematic Review, Molecules](https://www.mdpi.com/1420-3049/30/11/2376)
10. [Dynamic Construction, Perception, and Remodeling of Plant Cell Walls, Annual Review of Plant Biology](https://doi.org/10.1146/annurev-arplant-081519-035846)
11. [Zhang, B. et al. (2021). The plant cell wall: Biosynthesis, construction, and functions. Journal of Integrative Plant Biology.](https://onlinelibrary.wiley.com/doi/10.1111/jipb.13055)
12. [Atmodjo, M. A. et al. (2009). The structure, function, and biosynthesis of plant cell wall pectic polysaccharides.](https://www.sciencedirect.com/science/article/pii/S0008621509002006)
13. [Heterologous Rhamnolipid Biosynthesis: Advantages, Challenges, and Opportunities, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC7642724/)
14. [Guzman, E., Ortega, F., Rubio, R. G. (2024). Exploring the world of rhamnolipids. Current Opinion in Colloid & Interface Science 69, 101780.](https://www.sciencedirect.com/science/article/pii/S135902942300105X)
15. [Microbial production of rhamnolipids: opportunities, challenges and strategies, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC5544971/)
16. [Revista Politécnica 21(41), 47–77 (2025)](https://revistas.elpoli.edu.co/index.php/pol/article/download/2408/2384/15935)
17. [L-Rhamnose overview, ScienceDirect Topics](https://www.sciencedirect.com/topics/chemistry/l-rhamnose)
18. [How is Rhamnose Produced Commercially? Extraction & Biotech, Wellkr](https://wellkr.com/how-is-rhamnose-produced-commercially)
19. [US5077206A – Process for preparing L-rhamnose, Google Patents](https://patents.google.com/patent/US5077206)
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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Alcohols, ethers, and organooxygen groups › Alcohols and polyols*
*Initially written Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license