Abstract. Sukweenadi J, Yunita O, Setiawan F, Kartini, Siagian MT, Danduru AP, Avanti C. 2020. Antioxidant Activity Screening of Seven Indonesian Herbal Extract. Biodiversitas 21: 2062-2067. Kumis kucing (Orthosiphon stamineus), pegagan (Centella asiatica), seledri (Apium graveolens), kunyit (Curcuma domestica), temulawak (Curcuma xanthorrhiza), tempuyung (Sonchus arvensis) and meniran (Phyllanthus niruri) are herbs that commonly used in the Indonesia folk medicine. The constituents that responsible for several important biological activities are phenolic and flavonoid compounds which also possess antioxidant activity. Antioxidant activity of those seven Indonesian herbal extracts was evaluated using DPPH, ABTS and FRAP methods. The extraction was done with the reflux method by using 80% ethanol as a solvent. The total phenol and total flavonoids from each herbal extract were measured using Folin–Ciocalteu reagent and spectrophotometry. Antioxidant activity results by DPPH method on O. stamineus, C. asiatica, A. graveolens, C. domestica, C. xanthorrhiza, S. arvensis, and P. niruri showed IC50 value at 132; ND; 2221; 361; 538; 1118; and 102 ppm, respectively. Results from ABTS method, showed IC50 value at 22; 1199; 169; 100; 82; 143; and 20 ppm respectively. While results from the FRAP method showed that the ethanolic extract of P. niruri at a concentration of 20 ppm possesses the strongest antioxidant activity (17.41 ppm AEAC/ppm extract). The content of total phenolic compounds are 22.50; 0.67; 2.16; 11.40; 7.80; 7.22; and 2.62% GAE, while the total flavonoid compounds were 19.88; 6.67; 4.06; 71.02; 34.62; 3.78; and 8.34% QE, respectively. It can be concluded that ethanolic extract of P. niruri and O. stamineus obtain the highest antioxidant activity based on DPPH, ABTS and FRAP method.
A series of studies have been conducted to develop a heat-stable liquid oxytocin formulation. Oxytocin degradation products have been identified including citrate adducts formed in a formulation with citrate buffer. In a more recent study we have found that divalent metal salts in combination with citrate buffer strongly stabilize oxytocin in aqueous solutions (Avanti, C.; et al. AAPS J. 2011, 13, 284−290). The aim of the present investigation was to identify various degradation products of oxytocin in citrate-buffered solution after thermal stress at a temperature of 70°C for 5 days and the changes in degradation pattern in the presence of divalent metal ions. Degradation products of oxytocin in the citrate buffer formulation with and without divalent metal ions were analyzed using liquid chromatography−mass spectrometry/mass spectrometry (LC−MS/MS). In the presence of divalent metal ions, almost all degradation products, in particular citrate adduct, tri-and tetrasulfides, and dimers, were greatly reduced in intensity. No significant difference in the stabilizing effect was found among the divalent metal ions Ca 2+ , Mg 2+, and Zn 2+ . The suppressed degradation products all involve the cysteine residues. We therefore postulate that cysteine-mediated intermolecular reactions are suppressed by complex formation of the divalent metal ion and citrate with oxytocin, thereby inhibiting the formation of citrate adducts and reactions of the cysteine thiol group in oxytocin.
In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+ and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of aqueous oxytocin solutions was determined by RP-HPLC and HP-SEC after 4 weeks of storage at either 4°C or 55°C. Addition of sodium or potassium ions to acetate- or citrate-buffered solutions did not increase stability, nor did the addition of divalent metal ions to acetate buffer. However, the stability of aqueous oxytocin in aqueous formulations was improved in the presence of 5 and 10 mM citrate buffer in combination with at least 2 mM CaCl2, MgCl2, or ZnCl2 and depended on the divalent metal ion concentration. Isothermal titration calorimetric measurements were predictive for the stabilization effects observed during the stability study. Formulations in citrate buffer that had an improved stability displayed a strong interaction between oxytocin and Ca2+, Mg2+, or Zn2+, while formulations in acetate buffer did not. In conclusion, our study shows that divalent metal ions in combination with citrate buffer strongly improved the stability of oxytocin in aqueous solutions.
ABSTRACT:The aim of this study was to investigate the effect of divalent metal ions (Ca, Mg 2+ , and Zn 2+ ) on the stability of oxytocin in aspartate buffer (pH 4.5) and to determine their interaction with the peptide in aqueous solution. Reversed-phase high-performance liquid chromatography and high-performance size-exclusion chromatography measurements indicated that after 4 weeks of storage at 55 • C, all tested divalent metal ions improved the stability of oxytocin in aspartate-buffered solutions (pH 4.5). However, the stabilizing effects of Zn 2+ were by far superior compared with Ca 2+ and Mg 2+ . Liquid chromatography-tandem mass spectrometry showed that the combination of aspartate and Zn 2+ in particular suppressed the formation of peptide dimers. As shown by isothermal titration calorimetry, Zn 2+ interacted with oxytocin in the presence of aspartate buffer, whereas Ca 2+ or Mg 2+ did not. In conclusion, the stability of oxytocin in the aspartate-buffered solution is strongly improved in the presence of Zn 2+ , and the stabilization effect is correlated with the ability of the divalent metal ions in aspartate buffer to interact with oxytocin. The reported results are discussed in relation to the possible mode of interactions among the peptide, Zn 2+ , and buffer components leading to the observed stabilization effects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.