Department Medical Microbiology, Section Experimental Virology, Jena University Hospital, Hans-Knöll-Str. 2, D-07745, Jena, Germany.
BMC Complement Med Ther. 2020 Dec 23;20(1):380. doi: 10.1186/s12906-020-03173-2.
Rhinoviruses and influenza viruses cause millions of acute respiratory infections annually. Symptoms of mild acute respiratory infections are commonly treated with over-the-counter products like ambroxol, bromhexine, and N-acetyl cysteine, as well as of thyme and pelargonium extracts today. Because the direct antiviral activity of these over-the-counter products has not been studied in a systematic way, the current study aimed to compare their inhibitory effect against rhinovirus and influenza virus replication in an in vitro setting.
The cytotoxicity of ambroxol, bromhexine, and N-acetyl cysteine, as well as of thyme and pelargonium extracts was analyzed in Madin Darby canine kidney (MDCK) and HeLa Ohio cells. The antiviral effect of these over-the-counter products was compared by analyzing the dose-dependent inhibition (i) of rhinovirus A2- and B14-induced cytopathic effect in HeLa Ohio cells and (ii) of influenza virus A/Hong Kong/68 (subtype H3N2)- and A/Jena/8178/09 (subtype H1N1, pandemic)-induced cytopathic effect in MDCK cells at non-cytotoxic concentrations. To get insights into the mechanism of action of pelargonium extract against influenza virus, we performed time-of-addition assays as well as hemagglutination and neuraminidase inhibition assays.
N-acetyl cysteine, thyme and pelargonium extract showed no or only marginal cytotoxicity in MDCK and HeLa Ohio cells in the tested concentration range. The 50% cytotoxic concentration of ambroxol and bromhexine was 51.85 and 61.24 μM, respectively. No anti-rhinoviral activity was detected at non-cytotoxic concentrations in this in vitro study setting. Ambroxol, bromhexine, and N-acetyl cysteine inhibited the influenza virus-induced cytopathic effect in MDCK cells no or less than 50%. In contrast, a dose-dependent anti-influenza virus activity of thyme and pelargonium extracts was demonstrated. The time-of addition assays revealed an inhibition of early and late steps of influenza virus replication by pelargonium extract whereas zanamivir acted on late steps only. The proven block of viral neuraminidase activity might explain the inhibition of influenza virus replication when added after viral adsorption.
The study results indicate a distinct inhibition of influenza A virus replication by thyme and pelargonium extract which might contribute to the beneficial effects of these plant extracts on acute respiratory infections symptoms.
鼻病毒和流感病毒每年导致数百万例急性呼吸道感染。目前，对于轻度急性呼吸道感染的症状，通常使用氨溴索、溴己新和 N-乙酰半胱氨酸等非处方产品以及百里香和西洋耆提取物进行治疗。由于这些非处方产品的直接抗病毒活性尚未进行系统研究，因此本研究旨在比较它们在体外环境下抑制鼻病毒和流感病毒复制的效果。
在 Madin Darby 犬肾（MDCK）和 HeLa Ohio 细胞中分析氨溴索、溴己新和 N-乙酰半胱氨酸以及百里香和西洋耆提取物的细胞毒性。通过分析在 HeLa Ohio 细胞中，（i）浓度依赖性抑制鼻病毒 A2 和 B14 诱导的细胞病变效应，以及（ii）在 MDCK 细胞中，浓度非细胞毒性抑制流感病毒 A/Hong Kong/68（亚型 H3N2）和 A/Jena/8178/09（亚型 H1N1，大流行）诱导的细胞病变效应，比较这些非处方产品的抗病毒效果。为了深入了解西洋耆提取物对流感病毒的作用机制，我们进行了时效添加实验以及血凝和神经氨酸酶抑制实验。
在测试浓度范围内，N-乙酰半胱氨酸、百里香和西洋耆提取物在 MDCK 和 HeLa Ohio 细胞中无或仅有轻微的细胞毒性。氨溴索和溴己新的 50%细胞毒性浓度分别为 51.85 和 61.24 μM。在本体外研究中，未检测到非细胞毒性浓度下的抗鼻病毒活性。氨溴索、溴己新和 N-乙酰半胱氨酸在 MDCK 细胞中对流感病毒诱导的细胞病变效应的抑制作用不超过 50%。相比之下，百里香和西洋耆提取物表现出剂量依赖性的抗流感病毒活性。时效添加实验表明，西洋耆提取物抑制流感病毒复制的早期和晚期步骤，而扎那米韦仅作用于晚期步骤。已证实的病毒神经氨酸酶活性的阻断可能解释了当在病毒吸附后添加时，对流感病毒复制的抑制作用。
研究结果表明，百里香和西洋耆提取物对甲型流感病毒的复制有明显的抑制作用，这可能有助于这些植物提取物对急性呼吸道感染症状的有益作用。
