Isopimpinellin

Isopimpinellin is a furanocoumarin occurring in lime, expressed lime and rue oils. Unlike bergapten and psoralen, isopimpinellin is not phototoxic.

Skin. When confirmed to contain only trace amounts of psoralen, bergapten and methoxsalen, isopimpinellin is not phototoxic in chick skin bioassay. Earlier phototoxicity reports are attributed to contamination with highly active psoralens.

Mutagenicity. Not photomutagenic in studies. Not genotoxic or photogenotoxic in micronucleus assays.

Cancer. Significant anticancer activity. An oral dose of 70 mg/kg inhibited B[a]P-DNA adduct formation in mouse skin by 37 percent. At 35, 70 and 150 mg/kg it reduced mean papilloma counts by 49, 73 and 78 percent.

Isopimpinellin is a potent inhibitor of CYP1A1, suggesting an anticancer mechanism via blocking bioactivation of procarcinogens.

Since isopimpinellin is neither phototoxic nor photogenotoxic, the SCCP guideline for this compound should be revised in light of modern data.