Phanogracilins A–C, New Bibenzochromenones of Crinoid IPhanogenia gracilis/I

• Published in: Biomolecules (Basel, Switzerland) Vol. 14; no. 2
• Main Authors: Vasileva, Elena A, Berdyshev, Dmitrii V, Mishchenko, Natalia P, Gerasimenko, Andrey V, Menchinskaya, Ekaterina S, Pislyagin, Evgeniy A, Chingizova, Ekaterina A, Kaluzhskiy, Leonid A, Dautov, Salim Sh, Fedoreyev, Sergey A
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.01.2024
• Subjects: Analysis; Crinoidea; Organic compounds; Physiological aspects; Russia
• ISSN: 2218-273X; 2218-273X
• DOI: 10.3390/biom14020151

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.