每周分子 | Molecule of the Week

Original ACS 美国化学会 ACS美国化学会 2022-07-01

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每周分子：松萝酸

Molecule of the Week: Usnic acid

松萝酸是一种在地衣中发现的天然抗菌化合物。松萝酸不是羧酸，因为酚羟基的存在而使其具有酸性。松萝酸的pK_a值为4.4。

在19世纪40年代，德国和奥地利的科学家们从几种地衣属(如松萝属)中分离出了黄色的松萝酸；松萝酸由此得名。松萝酸味苦，以(R)-和(S)-对映异构体以及外消旋体的形式天然存在。本文展示了(R)-松萝酸的3D图像。

在松萝酸被首次分离的90多年后，英国利物浦大学的Frank H. Curd和Alexander Robertson阐明了松萝酸的结构。在他们的一系列文章中，报道了松萝酸及其许多衍生物的结构和实验室合成方法。

如危害信息表所示，松萝酸对健康和环境有害。尽管如此，它却仍是一些非处方膳食补充剂中的成分之一。Sloan Kettering肿瘤中心和其它知名组织已经警告不要使用松萝酸。

即使有危害，松萝酸仍然被用于医学研究，尤其是癌症研究。2012年，冰岛大学(位于雷克雅未克)的Helga M. Ogmundsdottir及其同事们曾报道，松萝酸会影响癌细胞中的线粒体和溶酶体的功能，对“自噬和pH值决定药物分布的治疗具有意义”。

2018年，浙江大学和杭州医学院人民医院的潘文胜及其同事们发现，松萝酸可诱导胃癌细胞周期阻滞、凋亡和自噬。

松萝酸信息速览

CAS 登记号	125-46-2
SciFinder命名	1,3(2H,9bH)-Dibenzofurandione, 2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-
分子式	C₁₈H₁₆O₇
摩尔质量	344.32 g/mol
外观	黄色晶体或粉末
熔点	204 ºC
水溶性	≈1 g/L

松萝酸危害信息

GHS*分类：急性毒性，口服，类别3
H301-吞咽有毒
GHS分类：皮肤腐蚀/刺激，类别2
H315-引起皮肤刺激
GHS分类：皮肤过敏，类别1
H317-可能引起皮肤过敏反应
GHS分类：严重眼损伤/眼刺激，类别2A
H319-引起严重眼睛刺激
GHS分类：特定目标器官毒性，单次暴露，呼吸道刺激，类别3
H335-可能引起呼吸道刺激
GHS分类：短期(急性)水生危害，类别1
H400-对水生生物有剧毒
GHS分类：长期(慢性)水生危害，类别1
H410-对水生生物毒性极大并具有长期影响

【关于每周分子】

自2001年以来，“每周分子”已成为广受欢迎的栏目。多数分子由读者推荐。每个结构都经由科学家审查，并以3-D和平面图像的形式显示，同时附有该分子简介。可以通过美国化学文摘社 (CAS) 提供的SciFinder中的CAS REGISTRY获取“每周分子”的更多信息。CAS REGISTRY中的每条物质信息都展示了物质的CAS登记号、索引名、通用名、商品名、书目信息等其他更多信息。发送邮件至motw@acs.org推荐您感兴趣的分子吧。

Usnic acid is a natural antibacterial compound found in lichens. It is not a carboxylic acid; instead, it gets acidity from the phenolic hydroxyl groups. Its pK_a is 4.4.

In the 1840s, German and Austrian scientists isolated yellow-colored usnic acid from several lichen genera, such as Usnea, from which it derives its name. The bitter-tasting acid exists naturally as its (R)- and (S)-enantiomers as well as the racemate. (R)-Usnic acid is shown in the 3-D image.

More than 90 years after its was isolated, usnic acid’s structure was elucidated by Frank H. Curd and Alexander Robertson* at the University of Liverpool (UK). In a long series of articles, these authors reported the structure and laboratory synthesis of usnic acid and many of its derivatives.

As shown in the hazard information table, usnic acid is hazardous to health and the environment. Nevertheless, it is an ingredient in some over-the-counter dietary supplements. The Memorial Sloan Kettering Cancer Center, among other reputable organizations, warns against using it.

Even with its hazards, usnic acid is being studied for medical applications, especially in cancer research. In 2012, Helga M. Ogmundsdottir and colleagues at the University of Iceland (Reykjavik) reported that it affects mitochondrial and lysosomal function in cancer cells and has “implications for therapeutic manipulation of autophagy and pH-determined drug distribution.”

More recently, in 2018, Wensheng Pan and co-workers at Zhejiang University and People’s Hospital of Hangzho found that usnic acid induces cycle arrest, apoptosis, and autophagy in gastric cancer cells.

Usnic acidfast facts

CAS Reg. No.	125-46-2
SciFinder nomenclature	1,3(2H,9bH)-Dibenzofurandione, 2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-
Empirical formula	C₁₈H₁₆O₇
Molar mass	344.32 g/mol
Appearance	Yellow crystals or powder
Melting point	204 ºC
Water solubility	≈1 g/L

Usnic acid information

Acute toxicity, oral, category 3
H301-Toxic if swallowed
Skin corrosion/irritation, category 2
H315-Causes skin irritation
Skin sensitization, category 1
H317-May cause an allergic skin reaction
Serious eye damage/eye irritation, category 2A
H319-Causes serious eye irritation
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3
H335-May cause respiratory irritation
Short-term (acute) aquatic hazard, category 1
H400-Very toxic to aquatic life
Long-term (chronic) aquatic hazard, category 2
H411-Toxic to aquatic life with long-lasting effects

About Molecule of the Week

MOTW has been a popular feature on ACS website since 2001. Many molecules are suggested by our website visitors. Every structure is reviewed by a scientist and displayed in 3-D and flat images with a brief description. Each week’s molecule also links to a sample record from the CAS REGISTRY, which is searched using SciFinder. Each record displays the registry number, index name and synonyms, bibliographic information, and more. Send us a molecule suggestion at motw@acs.org.

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