Secondary Metabolites from Alternaria sp., a Fungal Endophyte Isolated from the Seeds of Ziziphus jujuba

From the seeds of the traditional medicinal plant Ziziphus jujuba growing in Uzbekistan, the fungal endophyte Alternaria sp. was isolated. Extracts of this fungus grown on solid rice and liquid Wickerham culture media yielded 21 natural products. These natural products include the new phthalide natural product (±)7-methoxyphthalide-3-acetic acid (1) in addition to 20 known compounds including 19 polyketides and one alkaloid. Moreover, the OSMAC (One Strain MAny Compounds) approach is applied in this study. The unambiguous structure of the new compound was elucidated on the basis of one- and two-dimensional NMR spectroscopy in addition to HR-ESI-MS. Compounds 2, 3, 4, and 7 exhibited a cytotoxic activity against mouse lymphoma cell lines (L5178Y) with IC50 values of 1.7, 7.8, 6.8, and 6.2 μM, respectively when compared with the positive control kahalalide F (IC50 4.3 μM).