Photochemistry and Photobiology, 2003, 78(5): 470–474 The Alkaloid Brachycerine is Induced by Ultraviolet Radiation and is a Singlet Oxygen Quencher { Tatiana S. Gregianini y1 , Vivian C. da Silveira 1 , Diogo D. Porto 2 , Vitor A. Kerber 3 , Amelia T. Henriques 4 and Arthur G. Fett-Neto* 1,2 1 Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; 2 Departamento de Bota ˆnica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; 3 Faculdade de Farma ´cia, Universidade Federal do Parana ´, Curitiba, Parana ´, Braziland 4 Faculdade de Farma ´cia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil Received 20 February 2003; accepted 10 August 2003 ABSTRACT The effectsof ultraviolet(UV) radiation on chlorophyll contentand accumulation of the anti-inflammatory mono- terpene-indole alkaloid brachycerine in plants and calli of Psychotria brachyceras (Rubiaceae) were investigated. In this study,we also investigated a protective role for brachycerine against stress conditions. Calli and tip cuttings incubated in nutrient media were daily supplemented with 4 or 16 h of UV. High-performance liquid chromatography analyses of meth- anolic extracts showed only traces of brachycerinein irradiated aseptic cultures, with no alkaloid being observed in control calli. In cuttings, a 10-fold increase in brachycerine content was seen after exposure for 16 h to UV-C, whereas a 4 h daily supplementation doubled the amount of the alkaloid in leaves. Exposure to a UV-B source also doubled the alkaloid yield. In vitro brachycerine was able to quench singlet oxygen. The data indicate a potential protective role for brachycerine against UV radiation, acting as a UV filter (absorption peaks are within the UV range) and a reactive oxygen species scavenger. In addition,UV radiation may be used to increase yields of this compound of pharmaceutical interest. INTRODUCTION Secondary metabolites play a major role in the adaptation of plants to theirenvironment and also represent an important source of active pharmaceutical compounds. Approximately 25% of medi- cines currently used are derived from plants, and many of these are alkaloids. Alkaloidsoccurin approximately 20% of all plant species, and the number of identified structures exceeds 16 000 (1 These chemicals are low–molecular weightnitrogen-containing organic compounds, usually with a heterocyclic structure. Species of Psychotria from southern Brazil have been shown to contain novelbioactive indole alkaloids, some ofwhich display opioid analgesicproperties, cytotoxiceffectsand antibioticor anti- inflammatory activities(2,3).We haveinvestigated potential factorsregulating the accumulation of a monoterpenoid indole alkaloid from Psychotria brachyceras, i.e. brachycerine (Fig. 1). Psychotria brachyceras Muell. Arg. is a native shrub (1–3 m in height)widely distributed in tropical and subtropical forests of Brazil(4). A previousstudy hasshown nonspecific analgesic activity foran ethanolic alkaloid extract of the species (5), and a chemotaxis assay suggested an anti-inflammatory activity for th molecule (A. Henriques, unpublished). Terpenoid indoles are derived from the amino acid tryptophan, which is converted to tryptamine by the cytosolic enzyme tryptoph decarboxylase (TDC), and from isopentenyl diphosphate or dimethylallyl diphosphate via the triose phosphate–pyruvate path way (6).The condensation of tryptamine and secologanin gives strictosidine (6), which is regarded as the general precursor of all known terpenoid indole alkaloids. Different from the other known indole alkaloids, the structure of brachycerine suggests the direct condensation of tryptamine with 10-oxo-1-epi-loganin (7). This biogenetic hypothesis indicates an alternative pathway to produce these metabolites, leading to a new class of indole alkaloids. Studies using Catharanthus roseus as a model system showed thatterpene-indole alkaloids biosynthesis could be regulated by biotic and abiotic stimuli and may be activated at particular stages of plant development (8). Harmful ultraviolet (UV) wavelengths— UV-B (280–320 nm) and UV-C (200–280 nm)—can affect growth, development, photosynthesis, flowering, pollination and transpira- tion (9).Excess UV-B radiation, normally absorbed in the ozone layer, has been shown to be harmful to living organisms, affecting physiological and biochemical processes. Although UV-C is not relevant undernatural conditions of solarirradiance (10), it is extremely damaging to plants because UV-C photons are highly energetic, and high levels of damage can thus be generated quick (11).Such damages can be on DNA or at a physiological level. One of the main effects of UV is the enhanced production of reactive oxygen species (ROS) in several subcellular compart- {Posted on the website on 2 September 2003 *To whom correspondence should be addressed at: Centro de Biotecno- logia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonc¸alves 9500, Caixa Postal 15005, Porto Alegre, Rio Grande do Sul 91501-970, Brazil.Fax: 5551-3316-7309; e-mail: fettneto@dna.cbiot.ufrgs.br Currentaddress: Centro de Desenvolvimento Cientı ´fico e Tecnolo´ gico, Fundac¸a˜o Estadual de Produc¸a˜o e Pesquisa e Sau´ de (FEPPS), Porto Alegre, RS, Brazil. Abbreviations: Chl, chlorophyll; DABCO, 1,4-diazabicyclo[2.2.2]octane; HPLC, high-performance liquid chromatography; MS, Murashige & Skoog; ROS, reactive oxygen species; TDC, tryptophan decarboxylase; UV, ultraviolet. Ó 2003 American Society for Photobiology 0031-8655/03 $5.00þ0.00 470