New naphthoquinone derivatives from the marine-derived fungus Fusarium solani as potential fungicidal candidates against Lasiodiplodia theobromae
摘要
Plant diseases caused by Lasiodiplodia theobromae have expanded in both geographic range and host diversity, posing an increasing threat to agriculture and forestry. Owing to the limited understanding of these diseases and the lack of effective control strategies, the development of novel agricultural fungicides is urgently needed. In this study, eight new naphthoquinone derivatives (1–8), designated fusariumquinones A–H, respectively; two new enoic acids (9 and 10), designated fusariumacids A and B, respectively; and one new natural product (11), designated fusariumacid C, were isolated from the marine-derived fungus Fusarium solani XLGM24, obtained from Acanthus ebracteatus. Their structures and absolute configurations were elucidated using 1D and 2D NMR spectroscopy, HR-ESI-MS, the modified Mosher method, and time-dependent density functional theory electronic circular dichroism calculations. Notably, compound 2 exhibited significant antifungal activity against L. theobromae, with an EC50 value of 19.29 μg/mL, surpassing that of the positive control azoxystrobin (28.98 μg/mL). Mechanistic studies revealed that compound 2 disrupted the permeability and integrity of the cell membrane of L. theobromae, resulting in substantial morphological damage. Physiological assays demonstrated that compound 2 increased malondialdehyde levels, reduced soluble protein content, inhibited the activities of antioxidant enzymes, exacerbated oxidative stress, and disrupted the physiological metabolism of L. theobromae mycelia. In addition, compound 2 enhanced the innate defense responses of mango fruits, thereby increasing their resistance to L. theobromae. These findings identify compound 2 as a promising lead candidate for the development of novel fungicides.