psoralens

• psoralens = furanocoumarins
• funanorcumerins = lipid soluble -> fat layer, activated by UVA light = bind to macromolecules eg DNA
• furanocumerin activated within DNA base pairs (thymidine residues = primary target -> form monoadducts) + cross link dna =carcinogenic effect
• giant hogweed, celery, parsnips, cereriac
• > 22 furanocumerins in carrot family
• heat stable (protect plant even in sun)
• photosensitising = react with uva when in contact with skin
• flat + hydrophobic = absorbed in fat layer
• levels vary - genetic, infection (10x greater), tissue (celery seed = 3 mg/100g vs 0.2 mb /100g in stem), damage during harvest etc, higher near surface, lower than glycoalkaloids in potaotes
• uva contact -> erythematous = sunburn like blister
• burn only present upon uva chemical activation
• 12-36 h = erythematous (blisters), 1- 2 weeks = hyperpigmentation
• wavelength 350 - 365 nm optimal
• genotoxic + carcinogenic
• pharmaceutical use - 8-methoxypsoralen = psoriasis, skin conditions
• absorption of dietary dose = v low
• alcohol increases absorption - acts as solvent = enhanced solubility, irritate gut lining = ^ permeability