Sekikaic acid

Sekikaic acid is an organic compound in the structural class of chemicals known as depsides. It is found in some lichens. First isolated from Ramalina sekika, it is a fairly common lichen product in Ramalina and Cladonia, both genera of lichen-forming fungi. The species epithet of the powdery lichen Lepraria sekikaica refers to the presence of this substance—a rarity in genus Lepraria.

Properties
In its purified form, sekikaic acid exists as colourless rectangular prisms or rhombic plates. Its molecular formula is C22H2608. It has a melting point of 150 –. An ethanolic solution of sekikaic acid reacts with iron(III) chloride to produce a violet colour. Its ultraviolet spectrum has three peaks of maximum absorption (λmax) at 219, 263, and 303 nm.

Sekikaic acid has been demonstrated to have several biological activities in laboratory experiments. These include antioxidant activity, inhibition of the enzymes α-glucosidase and α-amylase, hypoglycemic activity, and lipid-lowering activity. It also has antiviral activity against Respiratory syncytial virus, even more so than the standard antiviral medication ribavirin.

Related compounds
The sekikaic acid contains similar compounds that are metabolically related to sekikaic acid. It comprises sekikaic acid as the major compound, and 4'O-demethylsekikaic and homosekikaic acids as satellite metabolites.