| Summary: | Two new xanthone derivatives, pestalotiones A (<b>1</b>) and B (<b>2</b>), one new diphenyl ketone riboside, pestalotione C (<b>7</b>), and one new diphenyl ether, pestalotione <span style="font-variant: small-caps;">D</span> (<b>8</b>), along with five known compounds isosulochrin dehydrate (<b>3</b>), 3,8-dihydroxy-6-methyl-9-oxo-9<i>H</i>-xanthene-1-carboxylate (<b>4</b>), isosulochrin (<b>5</b>), chloroisosulochrin (<b>6</b>), and pestalotether <span style="font-variant: small-caps;">D</span> (<b>9</b>), were isolated from the crude extract of the plant endophytic fungus <i>Pestalotiopsis theae</i> (N635). The structures of the new compounds were unambiguously deduced by HRESIMS and 1<span style="font-variant: small-caps;">D</span>/2<span style="font-variant: small-caps;">D</span>-NMR spectroscopic data. Compound <b>6</b> showed modest cytotoxicity against the HeLa cell line with an IC<sub>50</sub> value of 35.2 μM. Compound <b>9</b> also showed cytotoxic to the HeLa and MCF-7 cell lines, with IC<sub>50</sub> values of 60.8 and 22.6 μM, respectively. Additionally, compounds <b>1</b> and <b>2</b> exhibited antioxidant activity in scavenging DPPH radical with IC<sub>50</sub> values of 54.2 and 59.2 μg/mL, respectively.
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