Unusual antimalarial meroditerpenes from tropical red macroalgae
摘要:
Three antimalarial meroditerpenes have been isolated from two Fijian red macroalgae. The absolute stereochemistry of callophycolide A (1), a unique macrolide from Callophycus serratus, was determined using a combination of Mosher's ester analysis, circular dichroism analysis with a dimolybdenum tetraacetate complex, and conformational analysis using NOEs. In addition, two known tocopherols, beta-tocopherylhydroquinone (4) and delta-tocopherylhydroquinone (5), were isolated from Amphiroa crassa. By oxidizing 5 to the corresponding delta-tocopherylquinone (6), antimalarial activity against the human malaria parasite Plasmodium falciparum was increased by more than 20-fold. (C) 2010 Elsevier Ltd. All rights reserved.
Vitamin E hydroquinone is an endogenous regulator of ferroptosis via redox control of 15-lipoxygenase
摘要:
铁细胞凋亡是一种与炎症、神经变性和缺血有关的程序性细胞死亡。据报道,维生素 E(α-生育酚)可防止铁猝死,但其发生机制尚存争议。为了阐明维生素 E 活性的生化机制,我们在纹状体细胞模型中系统研究了维生素 E 的主要维生素和代谢物对脂质氧化和铁氧化的影响。我们发现,维生素 E 的一种特定内源性代谢物--α-生育酚对苯二酚,是一种比其母体化合物更有效的铁氧化抑制剂,它通过将酶的非血红素铁从活性的 Fe3+ 状态还原为非活性的 Fe2+ 状态来抑制 15-脂氧合酶。此外,维生素 E 的一种不可代谢的异构类似物保留了抗氧化活性,既不能抑制 15-脂氧合酶,也不能阻止铁跃迁。这些结果对维生素 E 主要作为非特异性亲脂抗氧化剂的流行模式提出了质疑。我们认为,与其他亲脂性维生素 A、D 和 K 相似,维生素 E 也是一种维生素原,其醌/氢醌代谢物具有抗铁细胞生成的细胞保护活性。