Molole Guyo Jilo, Gure Abera, Abdissa Negera
Department of Chemistry, College of Natural Science, Jimma University, P.O. Box 378, Jimma, Ethiopia.
BMC Chem. 2022 Jun 25;16(1):48. doi: 10.1186/s13065-022-00841-x.
In this study, total phenolic contents (TPC) and antioxidant activity of Commiphora mollis (Oliv.) Engl. (Burseraceae) resin were investigated. The resin was extracted using petroleum ether, chloroform, and methanol to give 27.46 ± 0.48, 46.56 ± 0.42, and 53.00 ± 1.39% extractable solids, respectively. The Folin-Ciocalteu (F-C) redox assay was optimized considering relevant parameters such as reaction time, maximum wavelength, and sample dilution effect before the determination of TPC. The concentration of antioxidants necessary to decrease by 50% the initial concentration of DPPH (EC) was determined at 60 min. The reaction kinetics was analyzed using the pseudo-first-order kinetics model. For the F-C assay, the optimum conditions for the maximum absorbance and analysis time were 760 nm and 30 min, respectively. Under these conditions, the method exhibited good sensitivity and linear instrumental responses over wide ranges of concentrations. The highest TPC;168.27 ± 3.44, 137.43 ± 1.32, and 136.16 ± 0.42 mgGAE/g were recorded in the diluted samples (500 µg/mL) of methanol, chloroform, and petroleum ether extracts, respectively. By using different concentrations of the test sample, exhaustive reduction of phenolics and/or antioxidant substrates was achieved. Regarding the DPPH radical scavenging capacity, the EC values for methanol, chloroform, and petroleum ether extracts were 295.03 ± 3.55, 342.75 ± 9.72, and 353.69 ± 7.30 µg/mL, respectively. The standard (L-ascorbic acid), however, exhibited much lower EC value (44.72 ± 0.48 µg/mL). The methanol extracts showed kinetic behavior (k values,115.08 to 53.28 M s; steady-state time, < 29 min) closer to that of L-ascorbic acid (k values, 190 to 109 M s; steady-state time, < 16 min), than other two extracts (k values,14 to 28 M s; steady-state time, 63 to 130 min). For all tested samples, the rate of the DPPH radical scavenging increases with concentration from 50 to 250 µg/mL. The current study demonstrated that the polar solvent (methanol) extract has a better F-C reducing capacity and DPPH radical scavenging activity than the nonpolar solvents extracts. This could be due to phenolics and other oxidation substrates extracted by methanol from the C. mollis resin. For a better understanding of the antioxidant constituents of the resin, a further study including isolation of its compounds is recommended.
在本研究中，对没药树（Commiphora mollis (Oliv.) Engl.，橄榄科）树脂的总酚含量（TPC）和抗氧化活性进行了研究。分别用石油醚、氯仿和甲醇对该树脂进行提取，得到的可提取固体含量分别为27.46±0.48%、46.56±0.42%和53.00±1.39%。在测定TPC之前，考虑反应时间、最大波长和样品稀释效应等相关参数，对福林-西奥尔特（F-C）氧化还原法进行了优化。在60分钟时测定将DPPH初始浓度降低50%所需的抗氧化剂浓度（EC）。使用伪一级动力学模型分析反应动力学。对于F-C测定法，最大吸光度和分析时间的最佳条件分别为760nm和30分钟。在此条件下，该方法在较宽的浓度范围内表现出良好的灵敏度和线性仪器响应。甲醇、氯仿和石油醚提取物的稀释样品（500μg/mL）中记录到的最高TPC分别为168.27±3.44、137.43±1.32和136.16±0.42mg GAE/g。通过使用不同浓度的测试样品，实现了酚类和/或抗氧化底物的彻底还原。关于DPPH自由基清除能力，甲醇、氯仿和石油醚提取物的EC值分别为295.03±3.55、342.75±9.72和353.69±7.30μg/mL。然而，标准品（L-抗坏血酸）的EC值低得多（44.72±0.48μg/mL）。甲醇提取物的动力学行为（k值为115.08至53.28M s；稳态时间<29分钟）比其他两种提取物（k值为14至28M s；稳态时间为63至130分钟）更接近L-抗坏血酸（k值为190至109M s；稳态时间<16分钟）。对于所有测试样品，DPPH自由基清除率在50至250μg/mL浓度范围内随浓度增加而增加。当前研究表明，极性溶剂（甲醇）提取物比非极性溶剂提取物具有更好的F-C还原能力和DPPH自由基清除活性。这可能是由于甲醇从没药树树脂中提取了酚类和其他氧化底物。为了更好地了解该树脂的抗氧化成分，建议进一步开展包括分离其化合物的研究。
