Phanogracilins A-C, New Bibenzochromenones of Crinoid
Phanogenia gracilis (Hartlaub, 1890).
Biomolecules 2024;
14:151. [PMID:
38397388 PMCID:
PMC10887160 DOI:
10.3390/biom14020151]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/17/2024] [Accepted: 01/24/2024] [Indexed: 02/25/2024] Open
Abstract
Three new bibenzochromenones named phanogracilins A-C (1-3) were isolated from the crinoid Phanogenia gracilis. The structure of 1 was established using X-ray crystallography as 5,5',6,6',8,8'-hexahydroxy-2,2'-dipropyl-4H,4'H-[7,9'-bibenzo[g]chromene]-4,4'-dione. This allowed us to assign reliably 2D NMR signals for compound 1 and subsequently for its isomer 2 that differed in the connecting position of two benzochromenone moieties (7,10' instead of 7,9'), and compound for 3 that differed in the length of the aliphatic chain of one of the fragments. Compound 4 was derived from 1 in alkaline conditions, and its structure was elucidated as 5,5',6',8,8'-pentahydroxy-2,2'-dipropyl-4H,4'H-[7,9'-bibenzo[g]chromene]-4,4',6,9-tetraone. Even though compounds 1-4 did not contain stereo centers, they possessed notable optical activity due to sterical hindrances, which limited the internal rotation of two benzochromenone fragments around C(7)-C(9'/10') bonds. Isolated bibenzochromenones 1-4 were tested for their antiradical, neuroprotective and antimicrobial activities. Compounds 1, 3 and 4 demonstrated significant antiradical properties towards ABTS radicals higher than the positive control trolox. Compounds 1 and 4 exhibited moderate neuroprotective activity, increasing the viability of rotenone-treated Neuro-2a cells at a concentration of 1 µM by 9.8% and 11.8%, respectively. Compounds 1 and 3 at concentrations from 25 to 100 μM dose-dependently inhibited the growth of Gram-positive bacteria S. aureus and yeast-like fungi C. albicans, and they also prevented the formation of their biofilms. Compounds 2 and 4 exhibited low antimicrobial activity.
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