L-Rhamnose

L-Rhamnose increases serum propionate after long-term supplementation, but lactulose does not raise serum acetate.[Pubmed: 15531673]

Am J Clin Nutr. 2004 Nov;80(5):1254-61.

Acute ingestion of the unabsorbed sugar L-Rhamnose in humans raises serum propionate, whereas acute ingestion of lactulose raises serum acetate. It is not known whether short-chain fatty acid concentrations in urine and feces reflect those in blood. The objective was to test the effects of oral L-Rhamnose and lactulose for 28 d on acetate and propionate concentrations in serum, urine, and feces.
METHODS AND RESULTS:
Eleven subjects ingested 25 g L-Rhamnose, lactulose, or d-glucose (control) for 28 d in a partially randomized crossover design. One fecal sample, hourly blood samples, and all urine samples were collected over 12 h on the last day of each phase. The increase in serum propionate was greater after L-Rhamnose than after lactulose (P < 0.05). The effect of lactulose on serum acetate was not significant, but lactulose raised the acetate:propionate ratio compared with d-glucose or L-Rhamnose in serum (P < 0.005) and urine (P < 0.02). Flatulence was significantly greater after lactulose and L-Rhamnose than after d-glucose (P < 0.0001), an effect that lasted 4 wk with lactulose but only 1 wk with L-Rhamnose.
CONCLUSIONS:
This study confirmed that L-Rhamnose ingestion over 28 d continues to selectively raise serum propionate in humans. Although serum acetate did not increase significantly after lactulose, the serum acetate:propionate ratio was significantly different after L-Rhamnose and lactulose, which suggests that these substrates could be used to examine the role of colonic acetate and propionate production in the effect of dietary fiber on lipid metabolism. Changes in the ratio of urinary acetate to propionate reflected those in serum.

L-rhamnose and L-fucose suppress cancer growth in mice.[Reference: WebLink]

Cent. Eur. J. Biol., 2011, 6(1):1-9.

It is documented that deficient fucosylation may play an important role in the pathogenesis of cancer. Since the supplementation of L-fucose could restore fucosylation in both in vitro and in vivo conditions, our intent was to examine the effect of intraperitoneal administration of L-fucose and L-Rhamnose (a similar deoxysaccharide) on tumour growth, mitotic activity and metastatic setting of a solid form of Ehrlich carcinoma as well as on the survival rate of tumour bearing mice.
METHODS AND RESULTS:
Both L-fucose and L-Rhamnose exerted a significant suppressive effect on tumour growth (P<0.05). After 10 days of therapy, the greatest inhibition of tumour growth expressed as a percentage of controls was observed in L-Rhamnose at a dose of 3 g/kg/day (by 62%) and L-fucose at a dose of 5 g/kg/day (by 47%). Moreover, the mitotic index decreased with increasing doses of L-fucose and L-Rhamnose. Prolonged survival of tumour bearing mice was observed after 14 consecutive days of daily administering L-Rhamnose. Its optimal dose was estimated to be 3.64 g/kg/day. L-Fucose, however, displayed only a slight effect on the survival of the mice.
CONCLUSIONS:
Our results suggest that L-fucose and especially L-Rhamnose have anticancer potential. This study is the first to demonstrate the tumour-inhibitory effect of L-Rhamnose.

The Aspergillus nidulans Zn(II)2Cys6 transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of α-L-rhamnosidases.[Pubmed: 25416526]

Microb Cell Fact. 2014 Nov 22;13(1):161.

Various plant-derived substrates contain L-Rhamnose that can be assimilated by many fungi and its liberation is catalyzed by α-L-rhamnosidases.Whilst induction is effected by L-Rhamnose, unlike many other glycosyl hydrolase genes repression by glucose and other carbon sources occurs in a manner independent of CreA.
METHODS AND RESULTS:
To date regulatory genes affecting L-Rhamnose utilization and the production of enzymes that yield L-Rhamnose as a product have not been identified in A. nidulans. In this study we have identified the rhaR gene in A. nidulans and Neurospora crassa (AN5673, NCU9033) encoding a putative Zn(II)2Cys6 DNA-binding protein. Genetic evidence indicates that its product acts in a positive manner to induce transcription of the A. nidulans L-Rhamnose regulon. rhaR-deleted mutants showed reduced ability to induce expression of the α-L-rhamnosidase genes rhaA and rhaE and concomitant reduction in α-L-rhamnosidase production. The rhaR deletion phenotype also results in a significant reduction in growth on L-Rhamnose that correlates with reduced expression of the L-rhamnonate dehydratase catabolic gene lraC (AN5672). Gel mobility shift assays revealed RhaR to be a DNA binding protein recognizing a partially symmetrical CGG-X11-CCG sequence within the rhaA promoter. Expression of rhaR alone is insufficient for induction since its mRNA accumulates even in the absence of L-Rhamnose, therefore the presence of both functional RhaR and L-Rhamnose are absolutely required. In N. crassa, deletion of rhaR also impairs growth on L-Rhamnose.
CONCLUSIONS:
To define key elements of the L-Rhamnose regulatory circuit, we characterized a DNA-binding Zn(II)2Cys6 transcription factor (RhaR) that regulates L-Rhamnose induction of α-L-rhamnosidases and the pathway for its catabolism in A. nidulans, thus extending the list of fungal regulators of genes encoding plant cell wall polysaccharide degrading enzymes. These findings can be expected to provide valuable information for modulating α-L-rhamnosidase production and L-Rhamnose utilization in fungi and could eventually have implications in fungal pathogenesis and pectin biotechnology.

Org Biomol Chem. 2014 Nov 14;12(42):8415-21.

Synthesis of L-rhamnose derived chiral bicyclic triazoles as novel sodium-glucose transporter (SGLT) inhibitors.[Pubmed: 25175761]

METHODS AND RESULTS:
Herein we describe the synthesis of a series of novel fused bicyclic 1,2,3-triazoles from commercially available, natural deoxy sugar, L-Rhamnose. The key reactions involved are (i) Zn(OTf)2 catalyzed enantioselective alkynylation of L-Rhamnose derived azidoaldehyde and (ii) deprotection of the acid sensitive 1,2-isopropylidene group followed by in situ intramolecular click-cycloaddition of azidoalkynols.
CONCLUSIONS:
Some compounds exhibit excellent sodium-glucose transporter (SGLT1 and SGLT2) inhibition activity.

Infect Immun. 1989 Jun;57(6):1691-6.

Heterogeneity of the L-rhamnose residue in the outer core of Pseudomonas aeruginosa lipopolysaccharide, characterized by using human monoclonal antibodies.[Pubmed: 2498204 ]

METHODS AND RESULTS:
Hybridoma cell lines producing human monoclonal antibodies (MAbs) MH-4H7 and KN-2B11 [immunoglobulin M (lambda)] which bound to the outer core region of Pseudomonas aeruginosa lipopolysaccharide (LPS) were established by cell fusion of human peripheral lymphocytes with human-mouse heteromyeloma SHM D-33. Both binding specificity experiments with a series of LPS-defective mutants derived from P. aeruginosa PAC1R (P. S. N. Rowe and P. M. Meadow, Eur. J. Biochem.132:329-337, 1983) and competitive enzyme immunoassay experiments with monosaccharides demonstrated that alpha-L-Rhamnose residues in the outer core of LPS might be in part an epitope. The MAbs specifically bound to clinical isolates belonging to Homma serotypes A, F, G, and K at a frequency of 70 to 86% and to serotypes H and M isolates at about 50%. They did not bind to any isolates of serotype B, E, and I tested.
CONCLUSIONS:
This evidence indicates that L-Rhamnose and probably its neighboring residues in the other core of P. aeruginosa are heterogeneous in some association with the O serotype.