You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Potent vasorelaxant analogs from chemical modification and biotransformation of isosteviol. Isosteviol (1) has been reported to exhibit moderate vasorelaxant activity. In order to enhance the bioactivity of this compound, chemical modification of 1 to the dihydro analog, ent-16β-hydroxybeyeran-19-oic acid (2), was undertaken. Compound 2 was then converted to the corresponding acetate derivative, ent-16β-acetoxybeyeran-19-oic acid (3). Biotransformation of compounds 1-3 by the fungus Cunninghamella echinulata NRRL 1386 was investigated and the metabolites 4-9 were obtained. The substrates and their metabolites were subjected to in vitro rat aorta relaxant activity evaluation. The metabolite 4, ent-7α-hydroxy-16-ketobeyeran-19-oic acid, exhibited the most highly potent activity, with EC50 of 3.46 nM, whereas the parent compound 1 showed relatively low activity (EC50 57.41 nM). A 17-fold increase in vasorelaxant activity of the analog 4 relative to compound 1 is of particular significant. Compound 4 exerted vasorelaxant activity at particularly low concentration and the vasorelaxant profile reached maximum at relatively low concentration, especially when compared with acetylcholine, the positive control.
{"Chemical": ["ent-16\u03b2-acetoxybeyeran-19-oic acid", "Isosteviol", "isosteviol", "acetate", "acetylcholine", "ent-7\u03b1-hydroxy-16-ketobeyeran-19-oic acid", "ent-16\u03b2-hydroxybeyeran-19-oic acid"]}