Department of Organic Chemistry, Institute of Chemistry, São Paulo State University, Araraquara 14800-900, Brazil.
Molecules. 2013 Feb 19;18(2):2376-85. doi: 10.3390/molecules18022376.
As part of our ongoing research on antioxidant agents from Brazilian flora, we screened the free radical scavenging activity of two extracts and eight fractions of Kielmeyera variabilis (Clusiaceae) using DPPH· (2,2-diphenyl-1-picrylhydrazyl-hydrate) and ABTS·+ [2,2'-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid)] colorimetric assays. The ethyl acetate and n-butanol fractions of the leaves of K. variabilis displayed the strongest activity (IC₅₀ of 3.5 ± 0.3 and 4.4 ± 0.2 μg mL⁻¹ for DPPH· and 6.6 ± 0.4 and 3.1 ± 0.1 μg mL⁻¹ for ABTS·+, respectively). Chromatographic fractionation of the most potent fractions led to identification of three flavonols with previously described antioxidant activity, quercitrin (1), quercetin-3-O-β-glucoside (3), and quercetin-3-O-β-galactoside (4), and of one biflavone, podocarpusflavone A (2). This is the first time that the presence of these flavonoids in Kielmeyera variabilis has been reported.
作为我们正在进行的巴西植物抗氧化剂研究的一部分，我们使用 DPPH·（2,2-二苯基-1-苦基肼水合物）和 ABTS·+ [2,2'-联氮双（3-乙基苯并噻唑啉-6-磺酸）]比色法筛选了 Kielmeyera variabilis（卫矛科）的两种提取物和八种馏分的自由基清除活性。K. variabilis 叶的乙酸乙酯和正丁醇馏分显示出最强的活性（DPPH·的 IC₅₀ 为 3.5 ± 0.3 和 4.4 ± 0.2 μg mL⁻¹，ABTS·+ 的 IC₅₀ 为 6.6 ± 0.4 和 3.1 ± 0.1 μg mL⁻¹）。最有效馏分的色谱分离导致鉴定出三种具有先前描述的抗氧化活性的类黄酮，槲皮苷（1），槲皮素-3-O-β-葡萄糖苷（3）和槲皮素-3-O-β-半乳糖苷（4），以及一种双黄酮，podocarpusflavone A（2）。这是首次报道这些类黄酮在 Kielmeyera variabilis 中的存在。
