Chemical Characteristics and In vitro Antidiabetic and Antioxidant Activities of Premna serratifolia L. Leaf Infusion and Decoction

Introduction: Leaves of Premna serratifolia L. (local name: arogo) is well known as food ingredient for fish/meat-based soup in Tentena, Indonesia. Evaluation of its bioactivities is needed. Objective: This study aimed to evaluate the α-glucosidase inhibitory and antioxidant activities of infusion and decoction of P. serratifolia leaves. Methods: The leaf samples were prepared by infusion and decoction and analysed for their α-glucosidase inhibitory and antioxidant activities, as well as total phenolic contents and LC-MS profiles. Results: The total phenolic content of the decoction was higher than the infusion. The UV spectra of both infusion and decoction showed peak at 325 nm and shoulder at 285 nm. Their LC-MS yielded one dominant component at 132 (100) m/z fragment, which was tentatively identified as caffeic acid. Both infusion and decoction extracts exhibited strong α-glucosidase inhibition with IC₅₀ of 4.27 and 0.046 μg GAE/ml, respectively. The IC₅₀ for DPPH scavenging activity of the infusion and decoction were similar; 6.82 and 7.28 μg GAE/ml, respectively. But the IC₅₀ of the infusion and decoction for ferrous ion chelating activities were different; 161.66 and 28.34 μg GAE/ ml, respectively. The α-glucosidase inhibitory and antioxidant activities were related to the phenolic content. Conclusion: The study concludes that both infusion and decoction of arogo leaves have antidiabetic effect and potential antioxidant activity. The decoction of the leaves may increase its antidiabetic capacity.