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:

Oil composition and characterisation of phenolic compounds of Opuntia ficus-indica seeds. The seed composition of four varieties of Opuntia ficus-indica growing in Algeria was investigated. Seeds ground into a fine powder were first, subjected to oil extraction and fatty acids analysis. The phenolic compounds were then extracted from the defatted powder of seeds in order to be quantified and characterised by liquid chromatography coupled to mass spectrometry (LC-MS(n)) and to nuclear magnetic resonance (LC-NMR) approaches. In addition, an evaluation of the antioxidant activity of the phenolic extracts was investigated. Gas chromatography analysis of the seed oil showed high percentages of linoleic acid in the four varieties ranging from 58% to 63%. The phenolic profile of the Opuntia ficus-indica seeds displayed a high complexity, with more than 20 compounds detected at 330nm after the LC separation. Among them, three isomers of feruloyl-sucrose were firmly identified and another was strongly supposed to be a sinapoyl-diglycoside. High correlations were found between phenolic content in the defatted seed extracts and their antioxidant activity. The data indicate that the defatted cactus seed wastes still contain various components that constitute a source for natural foods.
{"Chemical": ["phenolic", "fatty acids", "sinapoyl-diglycoside", "feruloyl-sucrose", "linoleic acid"]}