Chemical characterisation and a comparative study on multi-target biological activities of root part extracts of Coleus barbatus (Andrews) Benth. ex G. Don with its isolated compound, Forskolin

The present study aimed to comparatively investigate the chemical composition and biological activities of ethyl acetate extract of Coleus barbatus roots (CBREE), its non-polar fraction (CBREN) and polar fractions (CBREP), and the isolated diterpenoid compound forskolin. Chemical profiling of the extracts was performed using gas chromatography-mass spectrometry (GC-MS). In addition to biochemical assays, biological activities were evaluated in terms of antioxidant, in vitro anti-inflammatory, herbicidal, antibacterial, antifungal, and anti-feedant properties. GC-MS analysis led to the identification of 73 compounds accounting for 83.3% of the total composition of CBREE. In comparison, 74 and 57 components representing 87.2% and 78.7% of the total composition were identified in CBREN and CBREP fractions, respectively. CBREE was predominately composed of bornyl acetate (6.5%), decanal (6.5%), n-hexatriacontane (6.4%) and forskolin (4.6%). CBREN was dominated by 1-(1-heptadecynyl) cyclopentanol (7.7%), bornyl acetate (6.7%) and decanal (5.5%), whereas CBREP was characterized by a high abundance of forskolin (36.0%) and spiro4.5decan-7-one, 1,8-dimethyl-8,9-epoxy-4-isopropyl (6.1%). Biochemical assays revealed good to moderate levels of total phenolic content, total flavonoid content, and total orthodihydric phenols in the extracts. Both the extracts and the isolated compound forskolin exhibited significant antioxidant potential. Among the samples tested, forskolin demonstrated the highest in vitro anti-inflammatory activity (89.40%), followed by CBREE (86.37%), CBREP (82.78%) and CBREN (79.92%). Forskolin also exhibited superior herbicidal activity, showing greater inhibition of root and shoot growth compared to the extracts against Raphanus raphanistrum subsp. sativus seeds. Furthermore, forskolin displayed stronger antibacterial activity against Bacillus cereus and Escherichia coli than the crude extracts and fractions. The extracts and forskolin showed good to moderate antifungal activity against Alternaria alternata and Curvularia lunata. Notably, forskolin demonstrated pronounced anti-feedant activity compared to the extracts against third-instar larvae of Spilosoma obliqua. The isolated compound forskolin exhibited markedly higher biological activity than the crude extract and its fractions, particularly as an anti-inflammatory, herbicidal, antibacterial and anti-feedant agent. Based on these findings, Coleus barbatus can be considered a promising natural source for the development of environmentally benign pharmaceuticals and pesticides, owing to its rich bioactive profile, abundant availability, and wide global distribution.