The p-Terphenyl and Kavalactone Secondary Metabolites from the Fungus Hydnellum aurantiacum: Isolation and Evaluation of Their Effects on Platelet Activation

Phytochemical analysis of the tooth fungus Hydnellum aurantiacum resulted in the isolation of twenty-two compounds, including two new kavalactone derivatives—methylkavain (1) and aurapyrone (2); seven new p-terphenyl derivatives—ethylatromentin (3), 2-O-benzoylatromentin (4), aurantin (5), leucohydnelin (6), leucoaurantin (7), hydroxyleucoaurantiacin (8), benzoyltelephantin M (9); and thirteen known p-terphenyls—atromentin (10), aurantiacin (11), telephantin K (12), leucoatromentin (13), telephantin J (14), curtisian A (15), concrescenin B (16), telephantin L (17), dihydroaurantiacin dibenzoate (18), telephantin M (19), sarcodonin α (20), sarcodonin δ (21) and phellodonin (22). The structures were elucidated using spectroscopic methods (UV, NMR, HR-ESI-MS) along with comparison to literature data. All isolated substances, except 8 and 10, affected thrombin-induced human platelet activation at 90 μM: the seven compounds (9, 12, 16, 17, 20, 21, 22) potentiated it, while the remaining ones exhibited inhibitory activity with the strongest antiplatelet effects observed for 4, 5, and 7 (10.6 ± 4.0, 4.3 ± 3.2, 9.6 ± 2.9% of positive control, respectively). These and other p-terphenyl derivatives with antiplatelet activity identified in this study represent promising structures for further investigation into the mechanism of their action.