In-vitro anti-diabetic, anti-Alzheimer, anti-tyrosinase, antioxidant activities of selected coumarin and dihydroisocoumarin derivatives

Benzo-α-pyrone structured coumarin derivatives are secondary metabolites first obtained from Coumarouna odorata in 1822. Coumarin and its structural isomer dihydroisocoumarin derivatives are found in many different sources in nature. Several different bioactivities of these compounds have been reported. In this study, preliminary activity screening and comparison of four purchased coumarin derivatives (esculetin, esculin monohydrate, umbelliferon, scoparone) and four previously isolated 3-phenyl-3,4-dihydroisocoumarin derivatives (thunberginol C, scorzocreticoside I, scorzocreticoside II, scorzopygmaecoside) from a medicinal plant were carried out by in-vitro methods. α-Glucosidase, acetylcholinesterase, butyrylcholinesterase, tyrosinase inhibitor activities and antioxidant potentials of the compounds were evaluated. Consequently, thunberginol C (free – not glycosylated form of 3,4-dihydroisocoumarin structure) showed better potential in all enzyme inhibitory activities compared to coumarin structure. Particularly, α-glucosidase inhibitory activity of this compound with a very low IC50 value (94.76±2.98 µM) compared to standard acarbose (1036.2±2.70 µM) should be noted. Glycosylation and/or methoxy substitution of 3,4-dihydroisocoumarin structure resulted a significant decrease in all tested enzyme inhibitory activities. The structures of esculin MH, umbelliferone, scoparone, scorzocreticoside I, and scorzopygmaeceoside might be considered in further synthetic studies as selective acetylcholinesterase inhibitors. Thunberginol C has a promising potential in tyrosinase inhibitory activity. Esculetin and thunberginol C showed the best results with high potentials in antioxidant activity via 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical scavenging, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid cation radical decolorization, and cupric ion reducing antioxidant capacity assays compared to the standards.