Dose-response assessment of neuroactive botanical extracts and their bioactive constituents using microelectrode array (MEA) recordings in rat primary cortical cultures

Use of botanicals is increasing. While often considered as safe, neuromodulatory effects have been demonstrated previously. Establish the neuroactive potential of 13 botanical extracts. For 8 of these, we made a direct comparison with their major constituent. We used microelectrode array (MEA) recordings of primary rat cortical cultures to evaluate dose-response relationships on neuronal network function <i>in vitro</i>. Exposure to extracts from milk thistle, usnea, green tea, aristolochia, and ephedra mildly inhibited neuronal activity with distinct neuronal activity phenotypes. Extracts of tripterygium, yohimbe, kratom, and kava strongly inhibited neuronal activity. Despite differences in the degree of inhibition, all inhibitory extracts show No Observed Effect Levels (NOELs) of 1–5 µg/mL. Exposure to aconite, blue cohosh, goldenseal and oleander induced specific activity phenotypes characterized by hyperexcitation and/or intensification of (network) burst activity. While the extracts exhibit a narrow effective dose range, the extracts from aconite, goldenseal and oleander are most potent with NOELs of 0.25–0.5 µg/mL. Silybin B (milk thistle), epigallocatechin gallate (green tea), yohimbine (yohimbe), dihydrokavain (kava), mitragynine (kratom), aconitine (aconite), berberine (goldenseal) and oleandrin (oleander) were tested to investigate if the distinct neuronal activity phenotypes, indicative for the presence of multiple modes of action, are due to the known bioactive constituents of the extracts. For most constituents the activity phenotype is comparable to the extract, although the extract generally has a higher potency. Botanical extracts and constituents evoke diverse activity phenotypes, highlighting the complexity of hazard characterization of botanicals.

植物药制剂（botanicals）的应用日益广泛。尽管此类制剂通常被认为安全性良好，但过往研究已证实其具有神经调节作用。本研究旨在明确13种植物提取物的神经活性潜力。针对其中8种提取物，我们将其与各自的主要活性成分进行了直接对照。我们采用原代大鼠皮层神经元培养的微电极阵列（microelectrode array, MEA）记录技术，在体外（in vitro）条件下评估其对神经元网络功能的剂量-反应关系。水飞蓟（milk thistle）、松萝（usnea）、绿茶、马兜铃属植物（aristolochia）及麻黄属植物（ephedra）的提取物可轻度抑制神经元活动，并呈现出独特的神经元活动表型。雷公藤（tripterygium）、育亨宾树（yohimbe）、卡拉古吉那（kratom）及卡瓦胡椒（kava）的提取物则可强烈抑制神经元活动。尽管抑制程度存在差异，但所有具有抑制活性的提取物的未观察到效应水平（No Observed Effect Levels, NOELs）均为1~5 μg/mL。乌头属植物（aconite）、类叶升麻（blue cohosh）、北美黄连（goldenseal）及夹竹桃（oleander）的提取物可诱导特异性活动表型，其特征为神经元过度兴奋及/或（网络）爆发活动增强。尽管此类提取物的有效剂量范围较窄，但乌头属植物、北美黄连及夹竹桃的提取物活性最强，其未观察到效应水平为0.25~0.5 μg/mL。我们对水飞蓟宾B（silybin B，对应水飞蓟）、表没食子儿茶素没食子酸酯（epigallocatechin gallate，对应绿茶）、育亨宾（yohimbine，对应育亨宾树）、二氢卡瓦内酯（dihydrokavain，对应卡瓦胡椒）、米特拉吉宁（mitragynine，对应卡拉古吉那）、乌头碱（aconitine，对应乌头属植物）、小檗碱（berberine，对应北美黄连）及夹竹桃苷（oleandrin，对应夹竹桃）进行了测试，以探究这些独特的神经元活动表型（提示存在多种作用模式）是否由提取物中已知的生物活性成分所介导。对于大多数活性成分而言，其活动表型与对应提取物相似，但提取物通常具有更高的活性效价。植物提取物及其活性成分可诱发多样化的活动表型，这凸显了植物药制剂危害表征工作的复杂性。