AUTHOR=Liu Hongxin , Liu Zhaoming , Zhang Yanjiang , Chen Yuchan , Wang Huan , Tan Haibo , Zhang Weimin 

TITLE=Antioxidant Aryl-Substituted Phthalan Derivatives Produced by Endophytic Fungus Cytospora rhizophorae

JOURNAL=Frontiers in Chemistry

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.826615

DOI=10.3389/fchem.2022.826615

ISSN=2296-2646

ABSTRACT=<p>Six new phthalan derivatives cytorhizophins D-I (1-6) as well as three known derivatives cytorhizophin C, pestacin and rhizophol B were isolated from <italic>Cytospora rhizophorae.</italic> Among them, cytorhizophins D-E (1-2) and F-G (3-4) were two pairs of diastereoisomers, all of them featuring a 1-phenyl-1,3-dihydroisobenzofuran scaffold with a highly oxygenated <italic>O</italic>-linked <ext-link ext-link-type="uri" xlink:href="http://www.baidu.com/link?url=tDNvodsudWRW-nqJE-9Ss_nbfHbfMUWpYv81-DODfxeXEFOPngrkXgpKwkpC1E0-chIzKkBtsXqwVa5HX_VOTFnMhn_axYuPpU2AvOYmYMi" xmlns:xlink="http://www.w3.org/1999/xlink">isopentenyl</ext-link> unit. Besides, cytorhizophins H-I (5-6) represent the first examples of phthalide family with fascinating 6/6/6/5 tetracyclic ring system fusing as unprecedented furo [4,3,2-<italic>kl</italic>]xanthen-2 (10b<italic>H</italic>)-one skeleton. The structures of the new phthalan derivatives were extensively confirmed by detail spectroscopic analysis. The partial absolute configurations of compounds 1-6 were established through electronic circular dichroism (ECD) calculations. Moreover, compounds 1-4 showed remarkable antioxidant activities with EC<sub>50</sub> values ranging from 5.86 to 26.80 μM, which were better than or comparable to that of ascorbic acid (positive control).</p>