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:

Tetracyclic diterpenoids with isomerized isospongian skeleton and labdane diterpenoids from the fruits of Amomum kravanh. Four novel diterpenoids, including three tetracyclic diterpenes with isomerized isospongian skeletons, kravanhins A-C (1-3), and kravanhin D (4), and three new labdane diterpenes (5-7) were isolated from the fruits of Amomum kravanh. Compounds 1-4 had unprecedented isospongian diterpene skeletons with a trans-anti-cis fused tricyclic ring system. The structures of compounds 1-7 were established on the basis of extensive analysis of NMR spectra, CD, and X-ray crystallography. Compound 2 showed inhibitory activity on nitric oxide production in lipopolysaccharide-induced RAW264.7 macrophages with an IC(50) value of 36.2 μM.
{"Chemical": ["tetracyclic diterpenes", "isospongian", "labdane diterpenoids", "Tetracyclic diterpenoids", "isospongian diterpene", "kravanhin D", "diterpenoids", "kravanhins A-C", "nitric oxide", "labdane diterpenes"]}