GKK1032B from endophytic Penicillium citrinum induces the apoptosis of human osteosarcoma MG63 cells through caspase pathway activation

Chemical investigation of the culture extract of an endophytic Penicillium citrinum from Dendrobium officinale, afforded nine citrinin derivatives ( 1 – 9 ) and one peptide-polyketide hybrid GKK1032B ( 10 ). The structures of these compounds were determined by spectroscopic methods. The absolute configurations of 1 and 2 were determined for the first time by calculation of electronic circular dichroism (ECD) data. Among them, GKK1032B ( 10 ) showed significant cytotoxicity against human osteosarcoma cell line MG63 with an IC₅₀ value of 3.49 μmol·L^–1, and a primary mechanistic study revealed that it induced the apoptosis of MG63 cells via caspase pathway activation.