Accumulation of a bioactive triterpene saponin fraction of Quillaja brasiliensis leaves is associated with abiotic and biotic stresses Fernanda de Costa a , Anna Carolina Alves Yendo a , Juliane Deise Fleck b , Grace Gosmann c , Arthur Germano Fett-Neto a, d, * a Department of Botany, Graduate Program in Botany, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Porto Alegre 91501-970, RS, Brazil b Graduate Program in Environmental Quality, Feevale University, RS-239 2755, Novo Hamburgo 93352-000, RS, Brazil c Graduate Program in Pharmaceutical Sciences, Faculty of Pharmacy, UFRGS, Av. Ipiranga 2752, Porto Alegre 90610-000, RS, Brazil d Plant Physiology Laboratory, Graduate Program in Cell and Molecular Biology, Center for Biotechnology, UFRGS, Porto Alegre 91501-970, RS, Brazil article info Article history: Received 2 January 2013 Accepted 7 February 2013 Available online 16 February 2013 Keywords: Secondary metabolism Saponin Stress Quillaja brasiliensis abstract The saponins from leaves of Quillaja brasiliensis, a native species from Southern Brazil, show structural and functional similarities to those of Quillaja saponaria barks, which are currently used as adjuvants in vaccine formulations. The accumulation patterns of an immunoadjuvant fraction of leaf triterpene sa- ponins (QB-90) in response to stress factors were examined, aiming at understanding the regulation of accumulation of these metabolites. The content of QB-90 in leaf disks was significantly increased by application of different osmotic stress agents, such as sorbitol, sodium chloride and polyethylene glycol in isosmotic concentrations. Higher yields of bioactive saponins were also observed upon exposure to salicylic acid, jasmonic acid, ultrasound and UV-C light. Experiments with shoots indicated a significant increase in QB-90 yields with moderate increases in white light irradiance and by mechanical damage applied to leaves. The increased accumulation of these terpenes may be part of a defense response. The results herein described may contribute to further advance knowledge on the regulation of accumulation of bioactive saponins, and at defining strategies to improve yields of these useful metabolites. Ó 2013 Elsevier Masson SAS. All rights reserved. 1. Introduction Quillaja brasiliensis (A. St.-Hill. & Tul.) Mart. (Quillajaceae) is a saponin-producing tree native of Southern Brazil [1], commonly known as soap tree, due to the capacity of its leaves and barks to produce persistent foam in water. The saponins of this species showed remarkable similarities to those of the barks of Quillaja saponaria Molina, a related Chilean species and one of the main sources of industrial saponins used as adjuvant in vaccine formu- lations. A purified saponin fraction from leaves of the Brazilian species, named QB-90, was able to stimulate both Th1 and Th2 immune response, as well as the production of cytotoxic T-lym- phocytes against herpesvirus type 1 and 5 in mice, in a comparable manner to saponins from Q. saponaria (Quil-A Ò ) [2,3]. Saponins are secondary metabolites widely distributed in plants, characterized by the presence of a skeleton derived from a 30-carbon 2,3-oxidosqualene precursor, to which one or more sugar residues are linked [4,5]. The complex structure and its higher variability are factors responsible for difficulties in isolating and synthesizing these molecules [6]. These obstacles, associated with the often low concentration of saponins in biomass, highlight the need for developing ways to increase their content in plants prior to extraction. Secondary metabolite accumulation is usually stimulated in response to environmental challenges mediated by biotic or abiotic stresses, such as high and low temperatures, drought, salinity, Abbreviations: ABA, abscisic acid; DAB III, 10-deacetyl baccatin III; H 2 O 2 , hydrogen peroxide; HPLC, high pressure liquid chromatography; INMET, Instituto Nacional de Meteorologia (National Institute of Meteorology); INPE, Instituto Nacional de Pesquisas Espaciais (National Institute of Space Research); JA, jasmonic acid; MeJA, methyl jasmonate; MeSA, methyl salicylate; MS, Murashige and Skoog salts; NaCl, sodium chloride; O 2 - , superoxide anion; OH  , hydroxyl radical; P.A.R., photosynthetic active radiation; PEG, polyethylene glycol; PS II, photosystem II; QB- 90, purified saponin fraction from Q. brasiliensis; R/FR, red/far red light ratio; RMS, root mean square; ROS, reactive oxygen species; SA, salicylic acid; Th, T-lympho- cytes; US, ultrasound; UV, ultraviolet. * Corresponding author. Department of Botany, Graduate Program in Botany, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Porto Alegre 91501-970, RS, Brazil. Tel.: þ55 51 3308 7642; fax: þ55 51 3308 7309. E-mail addresses: fernandadecosta@yahoo.com.br (F. de Costa), anna.yendo@ yahoo.com.br (A.C.A. Yendo), julianefleck@yahoo.com.br (J.D. Fleck), grace.gosmann@ufrgs.br (G. Gosmann), fettneto@cbiot.ufrgs.br (A.G. Fett-Neto). Contents lists available at SciVerse ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy 0981-9428/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.plaphy.2013.02.003 Plant Physiology and Biochemistry 66 (2013) 56e62