Nova Biotechnologica 8-1 (2008) 79 SYNTHESIS AND PLANT GROWTH ACTIVITY OF 2-(4-OXOCHROMEN-3-YL)BENZOTHIAZOLIUM AND - BENZOXAZOLIUM BROMIDES MÁRIA HENSELOVÁ 1 , RENATA GAŠPAROVÁ 2 , MARGITA LÁCOVÁ 3 1 Department of Plant Physiology, Faculty of Natural Sciences, Comenius University, Mlynská dolina B-2, SK-842 15 Bratislava, Slovak Republic 2 Department of Chemistry, Faculty of Natural Sciences, University of SS. Cyril and Methodius, Námestie Jozefa Herdu 2, SK-917 01 Trnava, Slovak Republic 3 Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2, SK-842 15 Bratislava, Slovak Republic Abstract: A facile synthesis of novel 2-(4-oxochromen-3-yl) benzothiazolium bromides 4 and benzoxazolium bromide 5 using the one-pot condensation of substituted 4-oxochromene-3-carboxaldehydes 1 with 2-methylbenzothiazole (2a) or 2-methylbenzoxazole (2b) and benzyl bromide is described. The effects of benzothiazolium bromides 4 on the growth stimulation of the cucumber and retardant activity on corn seedlings were investigated. They inhibited growth of cucumber (root and hypocotyl) and shoots of corn at the range of 10 – 100 ppm and stimulated at 0.1 – 1 ppm concentrations. Keywords: plant growth activity, benzothiazolium, benzoxazolium salts, 4-oxochromene-3-carboxaldehydes 1. Introduction Benzothiazole derivatives represent a large group of heterocyclic substances, which were tested for a different biological activity (SUTORIS et al., 1988; KRÁĽOVÁ et al., 1994; EL-SHAAER et al., 1998). 2-R substituted benzotiazole derivatives manifested antibacterial and antifungal activities (AFSAH and NAYER 1996; MAGDOLEN et al., 2000; BUFFA et al., 2001) and are reported also to be active as antineoplastics agent (KRIEG and BILLITZ 1996). According ŠIMONOVÁ et al., (2005) ones were characterized as biologically active substances with dominant auxin-like growth promoting activity. 3-R substituted benzothiazole derivatives influenced the prolongation of growth, stimulated the plant regeneration, activity of peroxidase, and may induce the dedifferentiation and morphogenesis of plants in in vitro conditions (SUTORIS et al., 1993; HAVEL et al., 1994). Benzothiazole derivatives were also observed as protective agents against UV-induced mutagenesis in Euglena gracilis FOLTÍNOVÁ et al., (2003) and also against of cadmium stress HENSELOVÁ et al., (2007); KLECOVÁ - ŠIMONOVÁ et al. (2008) in Phytollaca dioica, Vigna radiata and Brassica juncea plants. A large number of 4-oxochromene derivatives occur in nature and exhibit variety of biological activities, e.g. antialgal (KRÁĽOVÁ et al., 1998), antifungal, antimycobacterial and antiparasitic (CAUJOLLE et al., 1993; LÁCOVÁ et al., 1995; GAŠPAROVÁ et al., 1997; NAWROT-MODRANKA et al., 2006), however, none of