Objective: Arginase inhibition could be a potential therapeutic approach for endothelial dysfunction. Syzygium cumini (L.) Skeels leaves containphenolic acids and flavonoids, which have been predicted to exhibit arginase inhibitory activity. Moreover, these leaves contain tannins, which canform complexes with enzymes and lead to false-positive results during biological testing. Therefore, this study was conducted to evaluate the arginaseinhibitory activity of S. cumini leaf extract and fractions as well as to elucidate the effects of tannins on this activity.Methods: S. cumini leaves were fractionated using n-hexane, ethyl acetate, and methanol. A colorimetric method was employed to evaluate arginaseinhibitory activity. Tannin elimination was performed through the gelatin precipitation method. Total phenolic and flavonoid contents of the fractionswere calculated using the Folin–Ciocalteu and aluminum chloride methods, respectively.Results: Ethyl acetate and methanol fractions showed arginase inhibitory activity with half-maximal inhibitory concentrations (IC50) of 46.96 and15.35 μg/mL, respectively. The methanol fraction was positive for tannins. After tannin elimination, this fraction exhibited less potent arginaseinhibitory activity, with an IC50 value of 53.03 μg/mL. The ethyl acetate fraction showed higher total phenolic and flavonoid contents than the methanolfraction.Conclusion: Tannins affected the arginase inhibitory activity of the methanol fraction of S. cumini leaves; however, the ethyl acetate fraction did notcontain tannins and could inhibit arginase activity.
Arginase inhibition and antioxidant activities may improve endothelial dysfunction. Previous studies demonstrated that Syzygium cumini leaves had pharmacological effects in diseases related to endothelial dysfunction, but there was no source linking the effect with arginase inhibitory activity. The aim of this study was to investigate arginase inhibitory and antioxidant activity of S. cumini leaves extract from different sources of simplisia, also determine its total phenolic content and gallic acid concentration. The leaves of S. cumini collected from Tangerang, Bogor and Sukoharjo city in Java, Indonesia. Arginase inhibition assay was done in vitro using colorimetric determination of urea which generated from L-arginine and arginase reaction. Antioxidant activity was evaluated using DPPH and FRAP methods. Total phenolic content of extract determined using Folin-Ciocalteu method. Gallic acid concentration was estimates using HPTLC. At a concentration of 50 µg/mL, all extracts exhibited arginase inhibition above 80%. However, the most active extract was sample collected from Bogor > Tangerang > Sukoharjo. Antioxidant activity of extract also came in that order. Determination of total phenolic content and gallic acid concentration of extracts revealed that S. cumini leaves collected from Bogor had the highest phenolic content (476.18 mgGAE/g) and gallic acid concentration (4.4 mg/g of extract). S. cumini leaves from different sources possessed different activity value on arginase inhibition, but not significant statistically. The leaves extract from Bogor, with the highest phenolic content and gallic acid concentration, showed the highest arginase inhibitory and antioxidant activity. Research Article
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