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:

Uncinataflavone, a new flavonoid with a methyl benzoate substituent from Selaginella uncinata. Uncinataflavone (1), a new flavonoid, together with four known compounds (2-5), was isolated from Selaginella uncinata (Desv.) Spring. Compounds 2 and 3 were isolated from the genus selaginella for the first time. The structure of the new compound was determined as methyl 3-(5,7-dihydroxy-2-(4-hydroxyphenyl)-4-oxo-4H-chromen-6-yl)-4-methoxybenzoate by means of spectroscopic evidence, including UV, IR, 1D and 2D NMR analyses as well as HR-ESI-MS. These compounds (1-5) were evaluated for the antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl assay system.
{"Chemical": ["1,1-diphenyl-2-picrylhydrazyl", "methyl benzoate", "Uncinataflavone", "flavonoid", "methyl 3-(5,7-dihydroxy-2-(4-hydroxyphenyl)-4-oxo-4H-chromen-6-yl)-4-methoxybenzoate"]}