Mohamed Abbas Umare Faruk, Michal Kořínek, Keerthana Shanmuganathan, Soundar Rajan Kulandhaivel, Sheng-Fan Wang, En-Liang Chu, Hui Chun Wang
The COVID-19 pandemic has underscored the urgent need for novel antiviral therapeutics that simultaneously target underlying inflammatory and allergic responses. M. koenigii (curry leaves), widely used in traditional medicine and culinary practices, is an abundant source of bioactive compounds. This study investigated the antiviral, anti-allergy, and anti-inflammatory properties of M. koenigii extracts and their purified constituents against SARS-CoV-2. Ethanolic leaf extracts were subjected to acid-base partitioning to enrich for alkaloid-containing fractions, which were further separated via medium-pressure and high-performance liquid chromatography. Bioactivity-guided fractionation yielded five major compounds, mahanimbine ( 1 ), mahanimbicine ( 2 ), mahanine ( 3 ), pheophorbide a ethyl ester ( 4 ), and pheophorbide b ethyl ester ( 5 ), which were identified by NMR and mass spectrometry. Compounds 4 and 5 were isolated for the first time from this genus and family. The isolated compound 4 inhibited SARS-CoV-2 spike RBD-ACE2 binding, docked with spike RBD, and reduced pseudoviral entry in cell-based assays. Compound 3 showed the strongest inhibitory effect in both antigen- and A23187-induced mast cell degranulation assays, supporting its anti-allergic potential. Compound 1 showed the strongest inhibition of TNF-α-induced NF-κB reporter activity in HEK-293T cells, indicating anti-inflammatory activity. Compounds 1 – 3 suppressed mast cell degranulation (40-75% inhibition at 40 μM) and TNF-α-induced NF-κB activation (45-90% inhibition at 20 μM). Compound 4 inhibited SARS-CoV-2 spike RBD-ACE2 binding (76% at 100 nM) and pseudovirus entry (68% at 30 μM). This study highlights curry leaf-derived alkaloids and chlorophyll derivatives with novel bioactivities, providing preliminary leads for research and development toward antiviral, anti-allergic, and anti-inflammatory properties.