Poulose Shibu M, Harris Edward D, Patil Bhimanagouda S
Vegetable and Fruit Improvement Center, Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843, USA.
J Nutr. 2005 Apr;135(4):870-7. doi: 10.1093/jn/135.4.870.
Citrus limonoid glucosides, a family of fruit bioactive compounds, were postulated to have free radical-scavenging and apoptosis-inducing properties against certain types of cancers. Four highly purified limonoid glucosides, limoin 17beta D-glucopypranoside (LG), obacunone 17beta D-glucopyranoside (OG), nomilinic acid 17beta D-glucopyranoside (NAG), and deacetylnomilinic acid 17beta D-glucopyranoside (DNAG) were tested for superoxide radical (O(2)(-))-quenching activity and cytotoxic action against undifferentiated human SH-SY5Y neuroblastoma cells in culture. All 4 scavenged O(2)(-) as measured by inhibition of pyrogallol decomposition in a spectrophotometric assay. Quenching by NAG in particular emulated an equivalent concentration of vitamin C. When added to the medium of SH-SY5Y cells in culture, micromolar amounts of LG and OG, compared with untreated controls, caused a cessation of cell growth and rapid cell death (P < 0.001); NAG and DNAG were better tolerated, but nonetheless toxic as well. Cytotoxicity was related to a concentration- and time-dependent increase in caspase 3/7 activity, suggesting that limonoid glucosides were capable of inducing apoptosis. Arrested cell growth and the induction of apoptosis were confirmed by flow cytometry and DNA fragmentation analysis. Importantly, caspase induction at 12 h correlated with cell survival at 24 h (P = 0.046), suggesting that apoptosis was the primary cause of cell death. We conclude that citrus limonoid glucosides are toxic to SH-SY5Y cancer cells. Cytotoxicity is exerted through apoptosis by an as yet unknown mechanism of induction. Individual limonoid glucosides differ in efficacy as anticancer agents, and this difference may reside in structural variations in the A ring of the limonoid molecule.
柑橘类柠檬苦素苷是一类水果生物活性化合物，据推测具有清除自由基和诱导某些类型癌症细胞凋亡的特性。对四种高度纯化的柠檬苦素苷，即柠檬苦素17β - D - 吡喃葡萄糖苷（LG）、奥巴昆酮17β - D - 吡喃葡萄糖苷（OG）、诺米林酸17β - D - 吡喃葡萄糖苷（NAG）和去乙酰诺米林酸17β - D - 吡喃葡萄糖苷（DNAG），进行了超氧阴离子自由基（O₂⁻）淬灭活性测试以及对培养的未分化人SH - SY5Y神经母细胞瘤细胞的细胞毒性作用测试。通过分光光度法检测邻苯三酚分解的抑制情况来测定，所有这四种化合物都能清除O₂⁻。特别是NAG的淬灭效果与同等浓度的维生素C相当。当向培养的SH - SY5Y细胞培养基中添加微摩尔量的LG和OG时，与未处理的对照相比，导致细胞生长停止和快速细胞死亡（P < 0.001）；NAG和DNAG的耐受性较好，但同样具有毒性。细胞毒性与caspase 3/7活性的浓度和时间依赖性增加有关，这表明柠檬苦素苷能够诱导细胞凋亡。通过流式细胞术和DNA片段化分析证实了细胞生长停滞和凋亡的诱导。重要的是，12小时时caspase的诱导与24小时时的细胞存活相关（P = 0.046），这表明凋亡是细胞死亡的主要原因。我们得出结论，柑橘类柠檬苦素苷对SH - SY5Y癌细胞有毒性。细胞毒性是通过一种尚未明确的诱导机制通过细胞凋亡来发挥作用的。单个柠檬苦素苷作为抗癌剂的功效不同，这种差异可能存在于柠檬苦素分子A环的结构变化中。
