Study on Comparative Chemical Composition and Biological Activities in the Essential Oils from Different Parts of Coleus barbatus (Andrews) Bent. ex G. Don

Abstract

The aim of the study was to compare the chemical composition and biological activities of Coleus barbatus aerial part essential oil (CBAEO) and Coleus barbatus root part essential oil (CBREO). The hydrodistilled essential oils (EOs) were analysed by gas chromatography-mass spectrometry (GC-MS) and biological activities were investigated in terms of antioxidant, in vitro anti-inflammatory, herbicidal, antibacterial, antifungal and antifeedant properties. GC-MS analysis led to the identification of 45 and 59 components contributing 86.7 % and 85.8 % in CBAEO and CBREO respectively. CBAEO was dominated by oxygenated monoterpenes (31.1 %) while CBREO was dominated by monoterpene hydrocarbons (29.1 %). The EOs exhibited good to moderate antioxidant potential assayed by DPPH radical, hydroxyl radical, nitric oxide radical and superoxide radical scavenging, reducing power and metal chelating activity. CBREO showed good anti-inflammatory activity (76.9 %) than CBAEO (64.7 %). Both the EOs exhibited moderate herbicidal potential against Raphanus raphanistrum subsp. sativus seeds. CBREO was observed to exhibit more antibacterial efficacy than CBAEO against Bacillus cereus and Escherichia coli. Both EOs exhibited significant antifungal activity against Alternaria alternata and Curvularia lunata and a strong antifeedant activity against third instar larvae of Spilosoma obliqua. The results obtained revealed strong to moderate efficacy of CBAEO and CBREO, which might serve as a bioactive source of natural antioxidants and an anti-inflammatory agent. The significant herbicidal, antimicrobial and anti-feedant activities of both the EOs might be helpful for the development of environmentally benign herbicides, fungicides and natural anti-feedant that could be an alternative of synthetic chemicals in future after proper clinical trials.