Lipoxygenases (LOXs) are potential treatment targets in a variety of inflammatory conditions. It is assumed that blocking the arachidonic acid (AA) metabolism via COX inhibition by either traditional NSAIDs or selective cyclooxygenase-2 (COX-2) inhibitors could lead to the generation of pro-inflammatory leukotrienes and lipoxins via the LOX pathway, partly accounting for the side effects seen with traditional NSAIDs and selective COX-2 inhibitors. To counter this, several LOX, phospholipase A2 (PLA2) inhibitors have been reported nowadays from natural sources. Cassia angustifolia (Vahl.) is a medicinal herb belonging to the family Leguminosae and their LOX inhibitory profiles are reported in this study. Results indicate that ethyl acetate extract of Cassia leaves could inhibit LOX. MS and IR data revealed the presence of aloe emodin (270.2 m/z) in the isolated fraction. Enzyme kinetics showed that aloe emodin inhibit Lipoxygenase competitively with an IC50 of 29.49 μM. Interaction of aloe emodin with LOX was also studied using fluorescence quenching method. ITC results indicate that the interaction of LOX with aloe emodin is endothermic in nature with a stoichiometry of n = 3. In conclusion, anti-inflammatory property of the plant could be assigned to the presence of aloe emodin.

中文翻译：

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芦荟大黄素对活性位点显示出高亲和力，而对其他两个位点显示出低亲和力，从而彻底降低了对脂肪氧化酶的抑制。

脂氧合酶 (LOX) 是多种炎症条件下的潜在治疗靶点。据推测，通过传统 NSAIDs 或选择性环氧化酶-2 (COX-2) 抑制剂通过 COX 抑制阻断花生四烯酸 (AA) 代谢可能导致通过 LOX 途径产生促炎性白三烯和脂氧素，部分原因是传统 NSAID 和选择性 COX-2 抑制剂的副作用。为了解决这个问题，现在已经报道了几种来自天然来源的 LOX、磷脂酶 A2 (PLA2) 抑制剂。狭叶决明 (Vahl.) 是一种属于豆科的药草，本研究报道了它们的 LOX 抑制谱。结果表明，决明子乙酸乙酯提取物对LOX具有抑制作用。MS 和 IR 数据显示芦荟大黄素的存在 (270. 2 m/z) 在分离的馏分中。酶动力学表明，芦荟大黄素以 29.49 μM 的 IC50 竞争性抑制脂肪氧化酶。还使用荧光猝灭法研究了芦荟大黄素与 LOX 的相互作用。ITC 结果表明 LOX 与芦荟大黄素的相互作用在性质上是吸热的，化学计量比为 3。总之，植物的抗炎特性可以归因于芦荟大黄素的存在。