New depsidones from Garcinia parvifolia and their antidiabetic, anti-tyrosinase, and antioxidant activities.

Abstract

In the search for potent bioactive compounds derived from medicinal plants, Garcinia parvifolia from East Kalimantan has demonstrated significant bioactivity consistent with established scientific criteria. Bioassay-guided isolation of the fruit extract resulted in two new depsidones named methyl garcidepsidone B (1) and parvifoliricodone A (6), two known analogues, a phloroglucinol, and a furfural derivative. Their structures were determined by spectroscopic techniques. The isolated compounds were subjected to assessments for their potential antidiabetic effects through an α-glucosidase inhibition assay, anti-tyrosinase activity, and antioxidant properties. Out of the isolated compounds, methyl garcidepsidone B (1) was the most potent inhibitor against α-glucosidase compared with acarbose as a positive standard. In the antioxidant assay, all isolated compounds showed significant free radical scavenging activity against ABTS, with the exception of compound 4. Regarding tyrosinase inhibitory activity, all isolated compounds exhibited low enzyme inhibition activity. Additionally, in silico molecular docking studies showed that compounds 1-3 exhibited favorable conformation and binding affinities within the enzymatic pockets of α-glucosidase. These findings indicate that the indigenous G. parvifolia fruit may serve as a natural source of antidiabetic, antioxidant, and anti-tyrosinase compounds, with potential for further pharmacological investigation.