Questiomycin A是由几种链霉菌以及一些真菌和细菌产生的吩恶嗪。Questiomycin A对细菌，真菌，植物和肿瘤细胞系具有弱活性，并抑制芳香酶和硫酸酯酶。Questiomycin与其他phenoxazines一样，在体外刺激细胞生长和更新，其活性可能与其形成稳定自由基的能力有关。最近，已显示出Questiomycin A抑制由小鼠黑素瘤细胞引起的肺转移。Questiomycin A和相关的吩恶嗪是发现研究中重要的重复复制标准，用于消除由于大量弱效活性物质而导致的铅。 Questiomycin A is a phenoxazine produced by several|Streptomyces|species and some fungi and bacteria. Questiomycin A is weakly active against bacteria, fungi, plants and tumour cell lines, and inhibits aromatase and sulfatases. Questiomycin, like other phenoxazines, stimulates cell growth and turnover|in vitro|, an activity possibly related to their ability to form stable free radicals. More recently, questiomycin A has been shown to inhibit pulmonary metastasis caused by mouse melanoma cells. Questiomycin A and related phenoxazines are important dereplication standards in discovery research to eliminate leads due to high amounts of weakly potent actives.