During a research program to identify new cholinesterase inhibitors of natural origin, two new 7,8-didehydroprotoberberine alkaloids (1 and 2) and nine known compounds (3–11) were isolated from the capsules of the common ornamental poppy, Papaver setiferum (previously P. pseudo-orientale). Despite their reported instability, the 7,8-didehydroprotoberberines isolated herein appeared relatively stable, particularly as their trifluoroacetic acid salts. The spatial distributions of the isolated alkaloids were also analyzed using desorption electrospray ionization imaging mass spectrometry. The alkaloids were localized predominantly within the walls and vascular bundles of the capsules, with the highest relative abundances occurring in the lower half of the capsules toward the peduncle. The relative abundances of the alkaloids were also compared across plant development stages. Although most alkaloids did not show clear patterns in their concentration across development stages, the concentration of suspected oxidation products clearly spiked upon plant death. Finally, all isolated natural products were screened for inhibitory activities against a panel of cholinesterases, from both human and animal sources. These studies identified several competitive inhibitors of cholinesterases with potency in the low micromolar range (1–4, 6, 7), offering new lead compounds for the development of cholinesterase inhibitory drugs.

Aphid control often relies on synthetic pesticides, but their overuse has raised concerns about resistance development and negative impact on wildlife and human health. Consequently, the search for new biopesticide agents has gained significant attention. Nemertide alpha-1, a peptide toxin from the marine nemertean worm Lineus longissimus (Gunnerus, 1770), is known for its pesticide activity but has less documented biological safety. This study investigates the aphid feeding deterrence and biological safety of the experimental biopesticide nemertide alpha-1. Nemertide alpha-1 demonstrated a clear dose-dependent repellent effect on the penetration behaviour of the green peach aphid (Myzus persicae, Sulzer). It also demonstrates bacteriostatic and bactericidal effects in an MIC (Minimum Inhibitory Concentration) assay, respectively, on E. coli (MIC: 112.5 µM) and S. aureus (MIC: 28.4 µM). In a bacterial liposome leakage assay, nemertide alpha-1 exhibits a less pronounced effect than the melittin control (20% maximum leakage at 100 µM), strengthening the hypothesis on the specificity of its neurotoxic mode of action. It is not toxic to mammalian cell U-937 GTB with only a slight decline in the percentage of survival at the highest concentration tested (80 µM). Finally, nemertide alpha-1 displays thermal stability over time for four weeks in three different conditions: cold (6 °C), room temperature (20–24 °C), and physiological temperature (37 °C). Nemertide alpha-1 deters green peach aphid feeding in the low micromolar range and exhibits low antimicrobial properties and very low toxicity to human cells. Its potential utility is further underscored by thermal stability over time.

Peptide toxins from marine invertebrates have found use as drugs and in biotechnological applications. Many marine habitats, however, remain underexplored for natural products, and the Southern Ocean is among them. Here, we report toxins from one of the top predators in Antarctic waters: the nemertean worm Parborlasia corrugatus (McIntosh, 1876). Transcriptome mining revealed a total of ten putative toxins with a cysteine pattern similar to that of alpha nemertides, four nemertide-beta-type sequences, and two novel full-length parborlysins. Nemertean worms express toxins in the epidermal mucus. Here, the expression was determined by liquid chromatography combined with mass spectrometry. The findings include a new type of nemertide, 8750 Da, containing eight cysteines. In addition, we report the presence of six cysteine-containing peptides. The toxicity of tissue extracts and mucus fractions was tested in an Artemia assay. Notably, significant activity was observed both in tissue and the high-molecular-weight mucus fraction, as well as in a parborlysin fraction. Membrane permeabilization experiments display the membranolytic activity of some peptides, most prominently the parborlysin fraction, with an estimated EC₅₀ of 70 nM.