RESEARCH ARTICLE The role of supplemental ultraviolet-B radiation in altering the metabolite profile, essential oil content and composition, and free radical scavenging activities of Coleus forskohlii, an indigenous medicinal plant Swabha Takshak 1 & S. B. Agrawal 1 Received: 30 June 2015 /Accepted: 10 December 2015 /Published online: 18 December 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract The effects of supplemental ultraviolet-B (s-UV-B; 3.6 kJ m −2 day −1 above ambient) radiation were investigated on plant metabolite profile, essential oil content and composi- tion, and free radical scavenging capacities of methanolic ex- tracts of Coleus forskohlii (an indigenous medicinal plant) grown under field conditions. Essential oil was isolated using hydrodistillation technique while alterations in metabolite pro- file and oil composition were determined via gas chromatography-mass spectroscopy (GC-MS). Leaf and root methanolic extracts were investigated via various in vitro as- says for their DPPH radical-, superoxide radical-, hydrogen peroxide-, hydroxyl radical-, and nitric oxide radical scaveng- ing activities, ferrous ion chelating activity, and reducing pow- er. Phytochemical analysis revealed the presence of alkaloids, anthocyanins, coumarins, flavonoids, glycosides, phenols, sa- ponins, steroids, tannins, and terpenoids. Oil content was found to be reduced (by ∼7 %) in supplemental UV-B (s- UV-B) treated plants; the composition of the plant extracts as well as essential oil was also considerably altered. Methanolic extracts from treated plant organs showed more potency as free radical scavengers (their EC 50 values being lower than their respective controls). Anomalies were ob- served in Fe 2+ chelating activity for both leaves and roots. The present study concludes that s-UV-B adversely affects oil content in C. forskohlii and also alters the composition and contents of metabolites in both plant extracts and oil. The results also denote that s-UV-B treated plant organs might be more effective in safeguarding against oxidative stress, though further studies are required to authenticate these findings. Keywords s-UV-B . Coleus forskohlii . Metabolite profile . Essential oil . Methanolic extracts . Free radical scavenging activities Abbreviations AsA Ascorbic acid BHT Butylated hydroxytoluene cAMP Cyclic adenosine monophosphate DAT Days after transplantation DPPH 1,1-Diphenyl-2-picrylhydrazyl EC Effective concentration GC-MS Gas chromatography-mass spectroscopy RNS Reactive nitrogen species ROS Reactive oxygen species UV Ultraviolet Introduction Coleus forskohlii (family Lamiaceae) is an indigenous medic- inal plant and has been used in Ayurvedic medicine since ancient times (Tripathi et al. 2013). In India, it grows wild in the sub-tropical Himalayas, Deccan peninsula, Bihar, and Gujarat and cultivated in parts of Maharashtra, Rajasthan, Gujarat, Karnataka, and Tamil Nadu on a commercial scale (Singh et al. 2011). It is the only natural source of forskolin (Shah et al. 1980), a labdane diterpenoid. Forskolin and C. Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-5965-6) contains supplementary material, which is available to authorized users. * S. B. Agrawal sbagrawal56@gmail.com 1 Laboratory of Air Pollution and Global Climate Change, Department of Botany, Banaras Hindu University, Varanasi 221 005, India Environ Sci Pollut Res (2016) 23:7324–7337 DOI 10.1007/s11356-015-5965-6