Sources, Chemistry, Biological Activity, and Biosynthesis of Natural Sulfoxides

Natural sulfoxides are a structurally diverse group of secondary metabolites bearing an S═O group with prominent medicinal and food/agricultural activities. Clinical sulfoxide drugs such as omeprazole and sulindac have stimulated interest in bioactive sulfoxides. In Allium vegetables, S-alk(en)yl cysteine sulfoxides determine flavor, aroma, and health properties, whereas glucosinolate-derived sulforaphane and isothiocyanates are major dietary chemopreventives in Brassica crops. Yet no comprehensive review has integrated their sources, chemistry, bioactivities, and biosynthesis. Here we summarize 302 naturally occurring sulfoxides reported up to September 2026, found in microorganisms, plants (mainly Amaryllidaceae and Brassicaceae), animals, and terrestrial/marine environments. They comprise organic sulfides (29%), peptides (23%), polyketides (9%), terpenes (6%), shikimates (5%), alkaloids (11%), carbohydrates (10%), fatty acids (1%), and amino acid-derived NPs (6%), showing cytotoxic, antimicrobial, anti-inflammatory, and enzyme–inhibitory activities. By highlighting food/agriculture sulfoxides, structure–activity relationships, and biosynthetic origins, this review provides leads for functional foods, biopesticides, and new pharmaceuticals.