Centre for Virus and Vaccine Research, Sunway University, Bandar Sunway, 47500, Subang Jaya, Selangor, Malaysia.
BMC Complement Med Ther. 2020 Mar 23;20(1):97. doi: 10.1186/s12906-020-2880-2.
The hand, foot and mouth disease (HFMD) is a febrile and exanthematous childhood disease mainly caused by Enterovirus 71 (EV-A71). In severe HFMD, virulent EV-A71 strains can cause acute flaccid paralysis and cardiopulmonary edema leading to death. Currently, no FDA approved antiviral treatment or vaccine is available for EV-A71. Flavonoids such as silymarin and baicalein are known to possess in vitro antiviral properties against viruses. In this study, the cytotoxicity and antiviral activity of silymarin, baicalein and baicalin were investigated.
The cytotoxic effects of three flavonoids towards rhabdomyosarcoma (RD) cells were first examined using cell proliferation MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay. Compounds found to be non-cytotoxic in RD cells were evaluated for their in vitro antiviral properties against the EV-A71 subgenotype B4 strain 41 (5865/SIN/000009) using antiviral assays. Viral infectivity was determined by reduction of the formation of plaques in RD cells. For the measurement of RNA copy number, the real time quantitative reverse transcription PCR (qRT-PCR) was used. The most potent compound was further evaluated to determine the mode of action of inhibition by time course, virus attachment and entry assays in Vero cells.
Silymarin was shown to exert direct extracellular virucidal effects against EV-A71 at 50% inhibitory concentration (IC) of 15.2 ± 3.53 μg/mL with SI of 10.53. Similarly, baicalein exhibited direct extracellular virucidal effects against EV-A71 at a higher IC value of 30.88 ± 5.50 μg/mL with SI of 13.64. Besides virucidal activity, silymarin was shown to block both viral attachment and entry of EV-A71 to inhibit infection in Vero cells.
Silymarin has a stronger inhibition activity against EV-A71 in comparison to baicalein. It could serve as a promising antiviral drug to treat EV-A71 infections.
手足口病（HFMD）是一种主要由肠道病毒 71 型（EV-A71）引起的发热性出疹性儿童疾病。在严重的 HFMD 中，毒力 EV-A71 株可引起急性弛缓性麻痹和心肺水肿导致死亡。目前，尚无获得美国食品和药物管理局（FDA）批准的针对 EV-A71 的抗病毒治疗或疫苗。水飞蓟素和黄芩素等黄酮类化合物已被证明具有体外抗多种病毒的特性。在这项研究中，研究了水飞蓟素、黄芩素和黄芩苷的细胞毒性和抗病毒活性。
首先使用细胞增殖 MTS [3-(4,5-二甲基噻唑-2-基)-5-(3-羧甲氧基苯基)-2-(4-磺苯基)-2H-四唑]测定法检查三种黄酮类化合物对横纹肌肉瘤（RD）细胞的细胞毒性作用。在 RD 细胞中发现无细胞毒性的化合物，使用抗病毒测定法评估其对肠道病毒 A71 亚基因型 B4 株 41（5865/SIN/000009）的体外抗病毒特性。通过减少 RD 细胞中斑块的形成来测定病毒感染力。为了测量 RNA 拷贝数，使用实时定量逆转录 PCR（qRT-PCR）。进一步评估最有效的化合物，以通过时间过程、病毒附着和进入测定法在 Vero 细胞中确定抑制作用的模式。
水飞蓟素对 EV-A71 具有直接的细胞外病毒杀灭作用，在 50%抑制浓度（IC）为 15.2±3.53μg/mL 时，SI 为 10.53。类似地，黄芩素对 EV-A71 具有更高的 30.88±5.50μg/mL 的 IC 值，SI 为 13.64，表现出直接的细胞外病毒杀灭作用。除了病毒杀灭活性外，水飞蓟素还能阻断 EV-A71 的病毒附着和进入，从而抑制 Vero 细胞的感染。
与黄芩素相比，水飞蓟素对 EV-A71 具有更强的抑制活性。它可以作为一种有前途的抗病毒药物来治疗 EV-A71 感染。
