A new Bioactive Annuionone from sunflower leaves

In a study carried out in search of natural herbicides, the potential of commercially grown sunflower varieties (Hybrid Supper-25, Gulshan-98 & Hybrid Suncross-42) was evaluated against Chenopodium album, Rumex dentatus, Coronopus didymus, Phalaris minor and Medicago polymorpha. The study started from early germination laboratory assays and was extended to field trials. From early germination bioassays, Suncross-42 was selected for further trials as it was found to be the most allelopathic against selected weeds and comparatively less toxic to wheat varieties. Among the various parts of the sunflower, leaf extract exhibited maximum potential in reducing the biomass of weeds. The efficacy of these extracts was also compared with commercially available herbicides. The highest tested extract concentration completely overcame weed crop competition by reducing the weed biomass and increasing wheat yield significantly. The extract found effective was then scanned for its chemical profile. Allelochemicals isolated and collected through several runs of High Performance Liquid Chromatography (HPLC) were checked again against selected weeds and those found most efficient were purified for their structural elucidation. Ten peaks were isolated from the dichloromethane fraction of sunflower leaf extract for structural elucidation. The P1 isolated as colourless oil gave molecular ion M-H⁺ at m/z 281.9 in the LC/negAPCI-MS spectrum. After the analysis of ¹³C NMR data this was found in good agreement with the molecular formula C₁₆H₂₆O₄ (calculated mass 282.272). The newly discovered compound was named as Annuionone H, which contains a similar basic cyclohexanone ring of Annuionone, the apocarotenoids reported by previous workers.