The Antiphytopathogenic Metabolites and the Synergy of Endophytes Paraphaeosphaeria sp., Nigrospora oryzae from the Same Ginkgo biloba Host

Two endophytes from the same Ginkgo biloba host were isolated and cultured separately. Three new eremophilane sesquiterpenoids (1–3), three new furan derivates (6, 8–9), one new polyketide (10), and four known compounds (4, 5, 7, 11) from Paraphaeosphaeria sp. and two new 10-membered macrolides (12–13), a new liner polyketide (14), a new benzofuran (15), and six known compounds (16–21) from Nigrospora oryzae were isolated. The structures of the isolated compounds were determined by spectroscopic methods, NMR calculations, and ECD calculations. The compounds 3–7, 9–10, 12, and 14–17 showed significant antiphytopathogenic effects against mycotoxigenic Alternaria sp. comparable to the activity of nystatin (positive control). Compounds 2, 6, 8, 9, and 18 indicated inhibitions against phytopathogen Fusarium asiaticum with MICs < 10 μg/mL. In addition, the compounds with weak antifungal activities from two endophytes were mixed to test their antifungal activity. The results showed that the metabolites from two endophytes had synergistic antifungal effects, and the beneficial interactions between natural products can induce more antifungal effects against plant pathogens than that of single compounds.