The essential oils obtained from the aerial parts and the roots of Conyza canadensis (L.) Cronquist (Asteraceae) at the flowering stage, collected from Turkey were simultaneously analysed by GC-FID and GC-MS. Forty-six components comprising 82.8% of the essential oil from the aerial parts and seven components comprising 96.7% of the roots oil were identified. Major constituents of the essential oil of the aerial parts were found to be limonene (28.1%), spathulenol (16.3%) and β-pinene (9.7%), whereas cis-lachnophyllum ester (86.5%), (2Z,8Z)-matricaria ester (3.9%) and β-pinene (2.3%) were identified to be main constituents in the volatiles of the root parts. In addition, antimicrobial activity of the essential oils was screened against Gram-positive and Gram-negative bacteria as well as one strain of fungus by broth microdilution method. Both of the essential oils exhibited antifungal activity against Candida albicans ATCC 10231 with 0.078 μg/ml MIC values. The highest antibacterial activity was observed by aerial parts oil against Escherichia coli RSKK 234 (MIC: 0.039 μg/ml). This is the first report on the chemical composition and antimicrobial activity of the essential oils obtained from C. canadensis growing in Turkey.

Cousinia is one of the widespread genera of Asteraceae family. This study aims to evaluate the biological activities and phytochemical compositions of C. iconica extracts. The antioxidant effects of the extracts were investigated on DPPH^•, ABTS^+•, and iron chelating methods, and the inhibition effects were tested on α-amylase, α-glucosidase, and tyrosinase, as well as AChE, and BChE enzymes. The quantitative and qualitative determinations of the compounds of the extracts were carried out by LC-MS/MS. As a result, the highest TPC (271.65 ± 3.32 mg GAE/g_extract), and TFC (4.79 ± 0.06 mg QE/g_extract) were found in C. iconica ethyl acetate (CIE) sub-extract. The highest antioxidant activity on DPPH^• (IC₅₀ = 90.397 ± 0.575 µg/mL) was shown in C. iconica methanol (CIM) extract. The highest ABTS^+•, and iron chelating activities were found in CIE with IC₅₀ = 70.70 ± 0.38, and 615.10 ± 2.47 µg/mL, respectively. The highest α-amylase, and tyrosinase activities were found in CIE, and C. iconica n-butanol sub-extract (CIB) with 864.57 ± 0.68, and 475.21 ± 6.22 µg/mL IC₅₀ values, respectively. AChE, and BChE activities were observed as the highest in CIB (IC₅₀ = 426.50 ± 3.78 µg/mL), and CIM (IC₅₀ = 330.54 ± 0.79 µg/mL), respectively. According to LC-MS/MS analyses, rutin, and cynarin were determined as the main constituents of CIM, and CIE. This is the first report that these biological activities and phytochemical compositions of C. iconica were investigated.