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:

New triterpenoids from the stem bark of Hypodaphnis zenkeri. A new pentacyclic triterpenoid and three new derivatives based on the taraxer-14-ene skeleton with a C-28 attached a carboxylic acid group have been isolated from the stem bark of Hypodaphnis zenkeri, together with six known compounds. The new product was identified as 2α,3α-dihydroxytaraxer-14-en-28-oic acid (1). Its derivatives, 2α,3α-diacetyltaraxer-14-en-28-oic acid (2), 2α,3α-di-O-carbonyl-2α,3α-dihydroxytaraxer-14-en-28-oic acid (3) and 2α,3α-dipropionyltaraxer-14-en-28-oic acid (4) were obtained by semisynthesis. The known compounds were identified as 3β-hydroxytaraxer-14-en-28-oic acid or aleuritolic acid (5) (McPhail, A.T., McPhail, D.R., Wani, M.C., Wall, M.E. & A.W., Nicholas, A.W. (1989). Identity of maprounic acid with aleuritolic acid. Revision of the structure of maprounic acid: X-ray crystal structure of p-bromobenzyl acetylmaprounate. Journal Natural Products, 52, 212), 3α-hydroxytaraxer-14-en-28-oic acid or isoaleuritolic acid (6), 3α-acetyltaraxer-14-en-28-oic acid acetate or aleuritolic acid acetate (7) (Chaudhuri, S.K., Fullas, F., Brown, D.M., Wani, M.C., Wall, M.E., Cai, L., … Kinghorn, A.D. (1995). Isolation and structural elucidation of pentacyclic triterpenoids from Maprounea africana. Journal of Natural Products, 58, 1-9), 3-oxo-taraxer-14-ene or taraxerone (8) β-sitosterol (9) and stigmasterol (10) (Kamboj & Saluja, 2011), together with fatty acids. Their structures were established on the basis of spectroscopic studies and chemical transformations.
{"Chemical": ["3\u03b2-hydroxytaraxer-14-en-28-oic acid", "aleuritolic acid", "2\u03b1,3\u03b1-diacetyltaraxer-14-en-28-oic acid", "3\u03b1-acetyltaraxer-14-en-28-oic acid acetate", "stigmasterol", "carboxylic acid", "maprounic acid", "triterpenoids", "2\u03b1,3\u03b1-dihydroxytaraxer-14-en-28-oic acid", "taraxerone", "2\u03b1,3\u03b1-di-O-carbonyl-2\u03b1,3\u03b1-dihydroxytaraxer-14-en-28-oic acid", "3\u03b1-hydroxytaraxer-14-en-28-oic acid", "aleuritolic acid acetate", "isoaleuritolic acid", "taraxer-14-ene", "\u03b2-sitosterol", "2\u03b1,3\u03b1-dipropionyltaraxer-14-en-28-oic acid", "p-bromobenzyl acetylmaprounate", "pentacyclic triterpenoid", "3-oxo-taraxer-14-ene"]}