Establishment of adventitious root cultures of Peritassa campestris (Celastraceae) was achieved from seed cotyledons cultured in semisolid Woody Plant Medium (WPM) supplemented with 2% sucrose, 0.01% PVP, and 4.0mg L-1 IBA. Culture period on accumulation of biomass and quinone-methide triterpene maytenin in adventitious root were investigated. The accumulation of maytenin in these roots was compared with its accumulation in the roots of seedlings grown in a greenhouse (one year old). A rapid detection and identification of maytenin by direct injection into an atmospheric-pressure chemical ionization ion trap tandem mass spectrometer (APCI-IT-MS/MS) were performed without prior chromatographic separation. In vitro, the greatest accumulation of biomass occurred within 60 days of culture. The highest level of maytenin-972.11 mu g.g(-1) dry weight-was detected at seven days of cultivation; this value was 5.55-fold higher than that found in the roots of seedlings grown in a greenhouse.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Univ Estadual Paulista, Nucleo Bioensaios Biossintese & Ecofisiol Prod Na, Dept Quim Organ, Inst Quim, BR-14801970 Araraquara, SP, BrazilUniv Estadual Paulista, Fac Ciencias Agron, Dept Prod Vegetal, BR-18610307 Botucatu, SP, BrazilUniv Ribeirao Preto, Dept Biotecnol Vegetal, BR-14096900 Ribeirao Preto, SP, BrazilUniv Estadual Paulista, Nucleo Bioensaios Biossintese & Ecofisiol Prod Na, Dept Quim Organ, Inst Quim, BR-14801970 Araraquara, SP, BrazilUniv Estadual Paulista, Fac Ciencias Agron, Dept Prod Vegetal, BR-18610307 Botucatu, SP, Brazil