Abstract Endophytic fungi isolated from Indonesian soursop (Annona muricata) leaves, which have the potential to treat breast cancer, have been successfully isolated since 2016. Identification based on the Internal Transcribed Spacer (ITS) gene revealed that fungi close to Phomopsis sp. The fungi were stored, subcultured, and extracted with ethyl acetate for in vitro and in vivo studies. To be registered as a medicinal ingredient and meet the requirements of the Indonesian Food and Drug Supervisory Agency (BPOM, Badan Pengawas Obat dan Makanan), it is necessary to ensure the standardization, safety, and quality of the Phomopsis extract. The results showed that the Phomopsis extract met the BPOM requirements for organoleptic, water, and solvent content, microbial and heavy metal contamination, total aflatoxin, and metabolite content. Analysis of the Phomopsis extract content also showed that the compounds in the two production batches were stable, with the highest relative abundance of 7-hydroxycoumarin. In silico studies with molecular docking show that the affinity energy of 7-hydroxycoumarin docking with the estrogen receptor alpha (ERα) and thymidine kinase 1 (TK1) has a lower negativity value than the comparison ligand (-6.7 and -6.8 kcal/mol).