Phenolic profile, antioxidant and antidiabetic activities of Medinilla eximia extracts from fruits, leaves and branches

Medinilla eximia an endemic plant from Kudus Regency, Central Java, Indonesia, and a member of the Medinilla genus in the Melastomataceae family, has been traditionally used for diabetes treatment. However, reports on chemical constituents, in vitro bioactivities, correlation studies, and metabolomic analysis remain limited. This research was targeted to analyse the total phenolics and flavonoids, along with the antioxidant and antidiabetic properties of M. eximia fruits, leaves, and fruit branches extracts. These extracts were obtained by maceration using methanol, ethyl acetate, dichloromethane, and n-hexane. Total phenolic content (TPC) and total flavonoid content (TFC) were spectrophotometrically calculated using Folin-Ciocalteu and aluminium chloride reagents, while the antioxidant properties were assayed through 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging methods. Antidiabetic activities were evaluated using α-amylase and α-glucosidase inhibitory assays. The methanol extracts of M. eximia exhibited the highest extraction yield, the greatest levels of phenolics and flavonoids, and demonstrated strong radical scavenging power and inhibitory properties. Furthermore, a robust positive correlation, as determined by Kendall's tau correlation analysis, was observed among phenolics, flavonoids, and antioxidant and antidiabetic capacities. Additionally, the chemometric analysis showed that the fruit methanol extract had the highest extraction yield and bioactivity relative to other extracts. Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) analysis revealed the presence of furaneol, 5-hydroxyveratric acid, and 2-[4-(3-hydroxypropyl)-2-methoxyphenoxy]-1,3-propanediol in the methanol extract. These findings indicate that extracts from M. eximia may be a valuable natural source of antioxidants and antidiabetic compounds.