**5. Conclusions**

This is the first systematic report on the phylogenetic diversity of fungi from mangrove *A. ilicifolius*. Four genera *Verticillium*, *Neocosmospora*, *Valsa*, and *Pyrenochaeta*, which were first isolated from mangroves, further enriched the diversity of mangrove fungi. Thirty-one strains of fungi displayed strong cytotoxicity to different cell lines, which was the important microbial resource for the discovery of cytotoxic compounds. Furthermore, by integrating cytotoxic activity-guided strategy and fingerprint analysis, a potent cytotoxic activity compound was quickly isolated from target active strains. This method, combining activityguided strategy with fingerprint analysis, could improve the efficiency of discovering active compounds.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/md20070432/s1, Table S1: Phylogenetic affiliations of cultivable fungi associated with *A. ilicifolius*. Figure S1: Phylogenetic tree of partial ITS gene sequences of mangrove-derived fungal strains. Reference sequences were downloaded from NCBI with the accession numbers indicated in parentheses. Figure S2: Phylogenetic tree of fungi in the order *Hypocreales* based on ITS gene sequence homology. Figure S3: The cytotoxicity relative inhibition rate data of the organic extracts in cancer cell lines. Figure S4. The fingerprint analysis of the organic extract of fungi from different species and genera. Figure S5. The fingerprint analysis of the organic extract of Penicillium sp. (HS-N-27).

**Author Contributions:** C.-F.W. contributed to isolation and identification of fungi, and manuscript preparation; J.M. and X.-X.H. contributed to related work of cytotoxic activity; Q.-Q.J., X.-Z.C. and L.C. contributed to fungal fermentation and chemical extraction. R.C. contributed to phylogenetic analysis. C.-L.S. contributed to NMR analysis and structure elucidation; C.-L.S., J.-Y.Z., X.-X.H. and M.-Y.W. were the project leader organizing and guiding the experiments and manuscript writing. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Fundamental Research Funds for the Central Universities (No. 202264001), the Program of National Natural Science Foundation of China (Nos. 41906090, 42006092, U1706210), Key Laboratory of Tropical Medicinal Resource Chemistry of Ministry of Education, Hainan Normal University (RDZH2021003 and RDZH2022002), the Research Fund of State Key Laboratory for Marine Corrosion and Protection of Luoyang Ship Material Research Institute (LSMRI) [No. KF190402], and the Taishan Scholars Program, China (No. tsqn20161010).

**Institutional Review Board Statement:** Not applicable.

**Data Availability Statement:** Data are contained within the article or Supplementary Material.

**Acknowledgments:** We thank Xiu-Li Zhang and Cong Wang at School of Medicine and Pharmacy, Ocean University of China for NMR test.

**Conflicts of Interest:** The authors declare no conflict of interest.
