Isolation, identification, and neuroprotective activity screening of secondary metabolites of endophytic Penicillium solitum from Pyrola incarnata Fisch

Abstract:

[Background] Pyrola incarnata Fisch (P. incarnata) has been widely used in the fields of food and medicine owing to the abundant chemical components with a variety of pharmacological activities. However, no report on the secondary metabolites of its endophytic fungi is available. [Objective] To isolate and identify the secondary metabolites of endophytic Penicillium solitum from P. incarnata and screen out the ones with anti-neuroinflammatory activity. [Methods] They were isolated and purified by column chromatography and preparative high performance liquid chromatography (HPLC). The structures were identified by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). Moreover, the anti-neuroinflammatory activity was verified in LPS-induced inflammatory BV-2 cells by reverse docking. [Results] A total of 12 compounds were isolated and identified:cyclopenin (1), dehydrocyclopeptin (2), viridicatin (3), p-hydroxybenzoic acid (4), indoleacetic acid (5), methyl compactin (6), cyclopeptine (7), cyclopenol (8), protocatechuic acid (9), viridicatol (10), N-[2-(3-indolyl)ethyl]malonamicacid (11), solitumidine A (12). Molecular docking showed that compound 11 had remarkable binding activity to p38 mitogen-activated protein kinase (p38) and extracellular regulated protein kinase 1 (ERK1) in mitogen-activated protein kinase (MAPK) signaling pathway which was associated with inflammation. In the experiment on BV-2 cells, compound 11 (10, 20 μmol/L) significantly improved the survival rate of BV-2 cells. Moreover, it inhibited the release of inflammatory factors (tumor necrosis factor-α, interleukin-1β, and interleukin-6) and nitric oxide (NO) in BV-2 cells induced by LPS. [Conclusion] Compound 11 is a new natural product with potential anti-neuroinflammatory activities, and the mechanism is the likelihood that it inhibits the expression of p38 and ERK proteins in MAPK signal pathway, which needs further investigation.