Menthofuran

Menthofuran is an organic compound found in a variety of essential oils including that of pennyroyal (Mentha pulegium). It is highly toxic and believed to be the primary toxin in pennyroyal responsible for its potentially fatal effects.^[1] After ingestion of menthofuran, it is metabolically activated to chemically reactive intermediates that are hepatotoxic.^[2]

Menthofuran

Names
IUPAC name 3,6-Dimethyl-4,5,6,7-tetrahydro-1-benzofuran
Identifiers
CAS Number	494-90-6 Y 17957-94-7 (R) Y 80183-38-6 (S) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:50542
ChemSpider	292309
ECHA InfoCard	100.007.087
PubChem CID	329983
UNII	LK024V9U3C Y 9N0IS8189W (R) Y OS9602CGD2 (S) Y
CompTox Dashboard (EPA)	DTXSID9025534
InChI InChI=1S/C10H14O/c1-7-3-4-9-8(2)6-11-10(9)5-7/h6-7H,3-5H2,1-2H3 Key: YGWKXXYGDYYFJU-UHFFFAOYSA-N InChI=1/C10H14O/c1-7-3-4-9-8(2)6-11-10(9)5-7/h6-7H,3-5H2,1-2H3 Key: YGWKXXYGDYYFJU-UHFFFAOYAW
SMILES o1c2c(c(c1)C)CCC(C2)C
Properties
Chemical formula	C10H14O
Molar mass	150.221 g·mol−1
Boiling point	208
Hazards
Flash point	86
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Biosynthesis

Menthofuran is produced biosynthetically from pulegone by the enzyme menthofuran synthase.

Menthofuran synthase converts pulegone to menthofuran

Chemistry

Synthesis

Menthofuran can be synthesized from 5-methylcyclohexane-1,3-dione and allenyldimethylsulfonium bromide in two steps via a furannulation strategy consisting of enolate addition and rearrangement.^[3]

Pharmacology

Menthofuran is a metabolite of pulegone. Both in vitro and in vivo studies have found the pulegone metabolite menthofuran to be an inhibitor of CYP2A6.^[4][5][6][7]

Menthofuran may deplete glutathione levels, leaving hepatocytes vulnerable to free radical damage.^[5]

References

1. Anderson IB, Mullen WH, Meeker JE, Khojasteh-BakhtSC, Oishi S, Nelson SD, Blanc PD (April 1996). "Pennyroyal toxicity: measurement of toxic metabolite levels in two cases and review of the literature". Annals of Internal Medicine. 124 (8): 726–34. doi:10.7326/0003-4819-124-8-199604150-00004. PMID 8633832. S2CID 24375611.
2. Thomassen D, Knebel N, Slattery JT, McClanahan RH, Nelson SD (1992). "Reactive intermediates in the oxidation of menthofuran by cytochromes P-450". Chemical Research in Toxicology. 5 (1): 123–30. doi:10.1021/tx00025a021. PMID 1581528.
3. Mariko Aso; Sakamoto, Mizue; Urakawa, Narumi; Kanematsu, Ken (1990). "Furannulation strategy. An efficient synthesis of fused 3-methylfurans". Heterocycles. 31 (6): 1003–6. doi:10.3987/com-90-5392.
4. Khojasteh-Bakh, S. C.; Koenigs, L. L.; Peter, R. M.; Trager, W. F.; Nelson, S. D. (July 1998). "(R)-(+)-Menthofuran is a potent, mechanism-based inactivator of human liver cytochrome P450 2A6". Drug Metabolism and Disposition. 26 (7): 701–704. PMID 9660853.
5. Gordon, W. P.; Huitric, A. C.; Seth, C. L.; McClanahan, R. H.; Nelson, S. D. (February 26, 1989). "The metabolism of the abortifacient terpene, (R)-(+)-pulegone, to a proximate toxin, menthofuran". Drug Metabolism and Disposition. 15 (5): 589–594. PMID 2891472.
6. Thomassen, D.; Pearson, P. G.; Slattery, J. T.; Nelson, S. D. (January 17, 1991). "Partial characterization of biliary metabolites of pulegone by tandem mass spectrometry. Detection of glucuronide, glutathione, and glutathionyl glucuronide conjugates". Drug Metabolism and Disposition. 19 (5): 997–104. PMID 1686249.
7. Kramlinger VM, von Weymarn LB, Murphy SE (May 2012). "Inhibition and inactivation of cytochrome P450 2A6 and cytochrome P450 2A13 by menthofuran, β-nicotyrine and menthol". Chemico-Biological Interactions. 197 (2–3): 87–92. Bibcode:2012CBI...197...87K. doi:10.1016/j.cbi.2012.03.009. PMC 3362486. PMID 22486895.