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:

Recent studies of antioxidant quinoline derivatives. Quinoline derivatives constitute an important class of compounds for new drug development. As a large number of experimental and theoretical studies have shown that the quinoline ring system is an important structural unit widely existing in alkaloids, therapeutics and synthetic analogues with exciting biological activities. The present review provides recent antioxidant activities covering in vivo and in vitro studies of natural and synthetic analogues, as well as the proposed mechanisms of action and structure-activity relationships.
{"Chemical": ["quinoline", "Quinoline"]}