Candindoles A and B, Heterozygous Terphenyl-Indole Alkaloids with Antifungal and Cytotoxic Activities from the Marine-Derived Fungus <i>Aspergillus candidus</i> HNNU0546

Three previously undescribed indole alkaloids, candindoles A-C (<b>1</b>-<b>3</b>), along with five known analogues (<b>4</b>-<b>8</b>), were isolated from the marine-derived fungus <i>Aspergillus candidus</i> HNNU0546. Structurally, <b>1</b> and <b>2</b> represent the first terphenyl-indole piperazine alkaloid hybrids featuring unprecedented backbones. Their structures including absolute configurations were elucidated by extensive spectroscopic methods, DP4+ probability analysis, and electronic circular dichroism (ECD) calculations. A plausible biosynthetic pathway for <b>1</b> is proposed. Compound <b>1</b> exhibited moderate growth-inhibitory activity against the plant pathogenic fungus of <i>Alternaria</i> sp. with an EC₅₀ value of 19.21 ± 0.26 μM, while compounds <b>1</b> and <b>2</b> showed significant cytotoxicity toward human rhabdomyosarcoma cells A673 with IC₅₀ values of 7.72 and 8.89 μM, respectively, comparable to the positive control cisplatin.