Badal Simone, Gallimore Winklet, Huang George, Tzeng Tzuen-Rong Jeremy, Delgoda Rupika
Natural Products Institute, Faculty of Pure and Applied Sciences, University of the West Indies, Mona, West Indies, Jamaica.
Org Med Chem Lett. 2012 Jun 11;2(1):21. doi: 10.1186/2191-2858-2-21.
Extracts from the marine algae Cymopolia barbata have previously shown promising pharmacological activity including antifungal, antitumor, antimicrobial, and antimutagenic properties. Even though extracts have demonstrated such bioactivity, isolated ingredients responsible for such bioactivity remain unspecified. In this study, we describe chemical characterization and evaluations of biological activity of prenylated bromohydroquinones (PBQ) isolated from the marine algae C. barbata for their cytotoxic and chemopreventive potential.
The impact of PBQs on the viability of cell lines (MCF-7, HT29, HepG, and CCD18 Co) was evaluated using the MTS assay. In addition, their inhibitory impact on the activities of heterologously expressed cytochrome P450 (CYP) enzymes (CYP1A1, CYP1A2, CYP1B1, CYP2C19, CYP2D6, and CYP3A4) was evaluated using a fluorescent assay.
7-Hydroxycymopochromanone (PBQ1) and 7-hydroxycymopolone (PBQ2) were isolated using liquid and column chromatography, identified using 1 H and 13 C NMR spectra and compared with the spectra of previously isolated PBQs. PBQ2 selectively impacted the viability of HT29, colon cancer cells with similar potency to the known chemotherapeutic drug, fluorouracil (IC50, 19.82 ± 0.46 μM compared to 23.50 ± 1.12 μM, respectively) with impact toward normal colon cells also being comparable (55.65 ± 3.28 compared to 55.51 ± 3.71 μM, respectively), while PBQ1 had no impact on these cells. Both PBQs had potent inhibition against the activities of CYP1A1 and CYP1B1, the latter which is known to be a universal marker for cancer and a target for drug discovery. Inhibitors of CYP1 enzymes by virtue of the prevention of activation of carcinogens such as benzo-a-pyrene have drawn attention as potential chemopreventors. PBQ2 potently inhibited the activity of CYP1B1 (IC50 0.14 ± 0.04 μM), while both PBQ1 and PBQ2 potently inhibited the activity of CYP1A1 (IC50s of 0.39 ± 0.05 μM and 0.93 ± 0.26 μM, respectively). Further characterizations showed partial noncompetitive enzyme kinetics for PBQ2 with CYP1B1 with a Ki of 4.7 × 10-3 ± 5.1 × 10-4 μM and uncompetitive kinetics with CYP1A1 (Ki = 0.84 ± 0.07 μM); while PBQ1 displayed partial non competitive enzyme kinetics with CYP1A1 (Ki of 3.07 ± 0.69 μM), noncompetitive kinetics with CYP1A2 (Ki = 9.16 ± 4.68 μM) and uncompetitive kinetics with CYP1B1 (Ki = 0.26 ± 0.03 μM) .
We report for the first time, two isolated ingredients from C. barbata, PBQ1 and PBQ2, that show potential as valuable chemotherapeutic compounds. A hydroxyl moiety resident in PBQ2 appears to be critical for selectivity and potency against the cancer colon cells, HT29, in comparison to the three other malignant cell lines studied. PBQs also show potency against the activities of CYP1 enzyme which may be a lead in chemoprevention. This study, the first on isolates from these marine algae, exemplifies the value of searching within nature for unique structural motifs that can display multiple biological activities.
此前研究表明，海洋藻类巴氏仙掌藻（Cymopolia barbata）的提取物具有良好的药理活性，包括抗真菌、抗肿瘤、抗菌和抗诱变特性。尽管提取物已显示出这种生物活性，但负责这种生物活性的分离成分仍未明确。在本研究中，我们描述了从海洋藻类巴氏仙掌藻中分离出的异戊烯基溴氢醌（PBQ）的化学特征及其细胞毒性和化学预防潜力的生物活性评估。
使用MTS法评估PBQ对细胞系（MCF-7、HT29、HepG和CCD18 Co）活力的影响。此外，使用荧光测定法评估它们对异源表达的细胞色素P450（CYP）酶（CYP1A1、CYP1A2、CYP1B1、CYP2C19、CYP2D6和CYP3A4）活性的抑制作用。
通过液相色谱和柱色谱分离出7-羟基仙掌藻色满酮（PBQ1）和7-羟基仙掌藻酮（PBQ2），利用¹H和¹³C NMR光谱进行鉴定，并与先前分离的PBQ光谱进行比较。PBQ2选择性地影响HT29结肠癌细胞的活力，其效力与已知化疗药物氟尿嘧啶相似（IC50分别为19.82±0.46 μM和23.50±1.12 μM），对正常结肠细胞的影响也相当（分别为55.65±3.28和55.51±3.71 μM），而PBQ1对这些细胞没有影响。两种PBQ对CYP1A1和CYP1B1的活性均有强效抑制作用，后者是已知的癌症通用标志物和药物发现的靶点。由于预防苯并[a]芘等致癌物的激活，CYP1酶抑制剂作为潜在的化学预防剂受到关注。PBQ2强效抑制CYP1B1的活性（IC50为0.14±0.04 μM），而PBQ1和PBQ2均强效抑制CYP1A1的活性（IC50分别为0.39±0.05 μM和0.93±0.26 μM）。进一步的表征显示，PBQ2与CYP1B1的酶动力学为部分非竞争性，Ki为4.7×10⁻³±5.1×10⁻⁴ μM，与CYP1A1为非竞争性动力学（Ki = 0.84±0.07 μM）；而PBQ1与CYP1A1显示部分非竞争性酶动力学（Ki为3.07±0.69 μM），与CYP1A2为非竞争性动力学（Ki = 9.16±4.68 μM），与CYP1B1为非竞争性动力学（Ki = 0.26±0.03 μM）。
我们首次报告了从巴氏仙掌藻中分离出的两种成分PBQ1和PBQ2，它们显示出作为有价值的化疗化合物的潜力。与研究的其他三种恶性细胞系相比，PBQ2中的羟基部分似乎对其对结肠癌细胞HT29的选择性和效力至关重要。PBQ对CYP1酶的活性也有抑制作用，这可能是化学预防的一个线索。这项关于这些海洋藻类分离物的首次研究，例证了在自然界中寻找可显示多种生物活性的独特结构基序的价值。
