The biotransformations of aroma compounds of spices, such as thymol (1), carvacrol (2), and eugenol (3), were investigated using cultured plant cells of Eucalyptus perriniana. Besides a beta-glucoside product (4, 3%), a biotransformation product, i.e., 5-methyl-2-(1-methylethyl)phenyl 6-O-(beta-d-glucopyranosyl)-beta-d-glucopyranoside (5, beta-gentiobioside, 87%), was isolated from the suspension cells after the five-day incubation of 1. On administration of 2, a beta-glucoside (6, 5%) and a beta-gentiobioside, i.e., 2-methyl-5-(1-methylethyl)phenyl 6-O-(beta-d-glucopyranosyl)-beta-d-glucopyranoside (7, 56%), were produced. Furthermore, E. perriniana cells also converted 3 into the corresponding beta-glucoside (8, 7%) and beta-gentiobioside (9, 58%). The cultured cells of E. perriniana are able to convert these aroma compounds of spices into glycosides which are accumulated in the cells.