Update on Chemistry and Biological Activities of Naturally Occuring Isocoumarins and 3,4-Dihydroisocoumarins (A Review)

Naturally occurring isocoumarins and dihydroisocoumarins emerged as a captivating class of compounds due to their structural diversity and multifaceted biological activities. It stands out as a group of metabolites, which are coumarin isomers with a reversed lactone moiety. They are synthesized by various organisms including plants, marine life, microbes, bacteria, and fungi. Our previous review covered the period 2016–2019, documenting nearly all natural products of this class. This updated review unravels the naturally occurring isocoumarins and dihydroisocoumarins by comprehensively exploring their structural elucidation and the broad spectrum of biological activities ranging from antimicrobial and anticancer properties to antitumour and enzyme inhibition. The classification and biological activities with structural elucidation revealed in our previous review are updated by the discovery of new members of this class. This review includes the most recent research on the structural variety and biological activity of these natural compounds.