Quinoline is found in alcoholic beverages. Quinoline is an alkaloid from various plant species including Mentha species. Also present in cocoa black tea and scotch whiskey.

Homoarbutin is a natural product.

Intermedin (human) is a polypeptide that can be found by peptide screening. Peptide screening is a research tool that pools active peptides primarily by immunoassay. Peptide screening can be used for protein interaction, functional analysis, epitope screening, especially in the field of agent research and development.