Antiviral alkaloids from Crinum jagus: Extraction, synergistic effects, and activity against dengue virus and human coronavirus OC43

<i>Crinum jagus</i>, a medicinal plant from the Amaryllidaceae family, possesses potent antiviral properties attributed to alkaloids such as cherylline and lycorine. This study evaluated various extraction methods--including continuous shaking, hot solvent, microwave-assisted, ultrasound-assisted, and liquid-liquid extraction using methanol, followed by ethyl acetate and subsequent acid-base to optimize the yield of bioactive compounds. The extraction method significantly influenced phenolic acid and alkaloid precursor content, with liquid-liquid extraction yielding the highest amounts. LC-MS/MS analyses confirmed the presence of major alkaloids in the extracts, notably cherylline and lycorine. The cytotoxic and antiviral properties of <i>C. jagus</i> extracts were assessed using a reporter-encoding dengue virus (DENV) vector and the β-coronavirus HCoV-OC43. LLE_E (liquid-liquid extract extract), enriched in phenolic compounds, was the most cytotoxic extract at concentrations above 0.6 μg/mL. Acid-base fractions, enriched in alkaloids, exhibited higher cytotoxicity than the methanol extracts counterparts, with significant cell death at concentrations above 2.5 μg/mL Additionally, the acid-base and LLE_E extracts were also the most efficient in inhibiting the replication of both HCoV-OC43 and DENV, with EC₅₀ values ranging from 1 to 2.5 μg/mL. The synergistic antiviral effect of cherylline with other <i>C. jagus</i> alkaloids was also evaluated, revealing that a combination of cherylline with gigantellinine strikingly reduced the flavivirus replication. These findings underscore the potential of <i>C. jagus</i> as a source of bioactive compounds with antiviral properties and highlight the importance of optimizing extraction methods to enhance specific applications.