Rose bengal

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Rose bengal
Systematic (IUPAC) name
4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein
Synonyms
C.I. 45440
Identifiers
CAS number	11121-48-5
PubChem	?
Chemical data
Formula	C₂₀H₄I₄Cl₄O₅
Molar mass	973.67 (sodium salt: 1017.65)
SMILES	O=C(O1)C2=C(C(Cl)=C(Cl)C(Cl)=C2Cl)C31 C4=C(C(I)=C(O)C(I)=C4)OC5=C(I)C(O)=C(I)C=C53
Complete data

Rose Bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is a stain. Its sodium salt is commonly used in eye drops to stain damaged conjunctival and corneal cells and thereby identify damage to the eye.

Absportion and extinction data can be found at: omlc.ogi.edu/spectra/PhotochemCAD/html/rosebengal.html [1]

The stain is also used in the preparation of Foraminifera for microscopic analysis, allowing the distinction between forms that were alive or dead at the time of collection.

A form of Rose Bengal is also being studied as a treatment for certain cancers. The company, Provectus Pharmaceuticals, renamed the drug PV-10 and is currently undergoing clinical trials for melanoma.

[edit] Chemical applications

Rose Bengal is also used in synthetic chemistry to generate singlet oxygen from triplet oxygen. The singlet oxygen can then undergo a variety of useful reactions, particularly [2 + 2] cycloadditions with alkenes and similar systems.

[edit] Biological applications

Rose Bengal is also used in animal models of ischemic stroke (photothrombotic stroke models) in biomedical research. A bolus of the compound is injected into the venous system. Then the region of interest, e. g. the cerebral cortex, is exposed and illuminated by LASER light of 561 nm. A thrombus is formed in the illuminated blood vessels, causing a stroke in the dependent brain tissue.

Rose bengal has been used for 50 years to diagnose liver and eye cancer. It has also been used as an insecticide.

The Sydney Melanoma Unit at Royal Prince Alfred Hospital is conducting a clinical trial in which individual tumours are injected with rose bengal.

Unit director John Thompson said within seven days the tumours become necrotic and die, and within 14 days they simply lift off the skin. Professor Thompson said an earlier trial of 20 patients showed between 60 and 80percent of tumours were successfully treated with one injection. The trial also found that rose bengal didn't affect healthy tissue and seemed to induce a beneficial immune system response that killed off other tumours that hadn't been injected. Not only injected tumour deposits undergo involution [reduction] and necrosis but non-injected 'bystander' lesions sometimes undergo involution as well.