Sulfoxide-Containing Bisabolane Sesquiterpenoids with Antimicrobial and Nematicidal Activities from the Marine-Derived Fungus <i>Aspergillus sydowii</i> LW09

Phytopathogens, such as phytopathogenic bacteria, fungi, and nematodes, have caused great losses of crops every year, seriously threatening human health and agricultural production. Moreover, marine-derived fungi are abundant sources of structurally unique and bioactive secondary metabolites that could be potential candidates for anti-phytopathogenic drugs. One new sulfoxide-containing bisabolane sesquiterpenoid aspersydosulfoxide A (<b>1</b>) and nine known analogues (<b>2</b>–<b>10</b>) were isolated from the marine-derived <i>A. sydowii</i> LW09. The absolute configuration of the sulfur stereogenic center in <b>1</b> was determined by electronic circular dichroism (ECD) calculations. Compound <b>5</b> showed inhibition activity against <i>Pseudomonas syringae</i>, with a minimum inhibitory concentration (MIC) value of 32 μg/mL, whereas, compounds <b>2</b>, <b>7</b>, and <b>8</b> showed antibacterial activities toward <i>Ralstonia solanacarum</i>, with the same MIC value at 32 μg/mL. Meanwhile, compounds <b>3</b>, <b>7</b>, and <b>8</b> inhibited the fungal spore germination of <i>Fusarium oxysporum</i>, with the half maximal effective concentration (EC₅₀) values of 54.55, 77.16, and 1.85 μg/mL, respectively, while compounds <b>2</b>, <b>3</b>, <b>7</b>, and <b>8</b> inhibited the fungal spore germination of <i>Alternaria alternata</i>, which could be induced by vacuolization of germ tubes, with EC₅₀ values of 34.04, 44.44, 26.02, and 46.15 μg/mL, respectively. In addition, compounds <b>3</b>, <b>7</b>, and <b>8</b> exhibited nematicidal activities against <i>Meloidogyne incognita</i> second-stage juveniles (J2s). In addition, compound <b>8</b> possessed the strongest nematicidal activity of nearly 80% mortality at 60 h with the half lethal concentration (LC₅₀) values of 192.40 μg/mL. Furthermore, compounds <b>3</b>, <b>7</b>, and <b>8</b> could paralyze the nematodes and then impair their pathogenicity.