Biotransformation of menthol and geraniol by hairy root cultures of Anethum graveolens: effect on growth and volatile components

The biotransformation capacity of Anethum graveolens hairy root cultures was determined by evaluation of the influence of the addition of menthol or geraniol on growth and volatile compounds production.

The substrate, menthol or geraniol, 25mg.l^-1, was added to the hairy root cultures 15 days after inoculation. The cultures were maintained for 7 weeks in SH medium [1], in darkness at 24°C and 80r.p.m. Growth was measured by the dissimilation method [2] and by fresh and dry weight determination. The volatile oils were extracted by distillation-extraction and analyzed by GC and GC-MS.

Substrate addition did not substantially influence growth. The constitutive volatile oils were composed, in more than 50%, by falcarinol (9–52%), apiole (9–24%), palmitic acid (7–16%), linoleic acid (4–9%), myristicin (2–8%) and n-octanal (2–8%). The relative amount of menthol quickly decreased in a period of 48h after addition (from 52% to 11%), and a concomitant production of menthyl acetate was observed (up to 55%). Geraniol was biotransformed in 10 new products, the alcohols linalool, α-terpineol and citronellol, the aldehydes neral and geranial, the esters citronellyl, neryl and geranyl acetates and, in trace amounts, linalool and nerol oxides. The relative proportion of geraniol quickly decreased in a period of 48h (from 20% to less than 3%) while the products increased (up to 55%). The relative amount of all the detected biotransformation products gradually decreased over culture time.

Anethum graveolens hairy root cultures showed biotransformation capacity that suggests the activity of enzymes such as redutases, isomerases and transacetylases, among others.

1. Schenk, U.R., Hildebrandt, A.C. (1972) Can. J. Bot. 50: 199–204.

2. Schripsema, J. et al. (1990) Plant Cell Tiss. Org. Cult. 22: 55–64.