Curcuma sp. “Khamin Oi” extracts inhibit human coronavirus OC43 replication in HCT-8 colorectal cell line

Plants belonging to the genus <i>Curcuma</i> have shown promise in exerting antiviral activity. In this study, <i>Curcuma</i> sp. "Khamin Oi" (CKO), a traditional Thai medicinal herb listed in Thai herbal pharmacopoeia, was subjected to extraction using a variety of solvents. Consequently, LC-MS/MS and GC-MS/MS analyses were conducted to assess the phytochemical profiles of all the crude extracts and identify the compounds potentially responsible for their antiviral effects. The antiviral effects of these extracts against the human coronavirus OC43 (HCoV-OC43) were also investigated. An in-cell ELISA was used to investigate the anti-HCoV-OC43 replication activity of the crude rhizome extracts of CKO. Among the extracts, the crude hexane extract of CKO exhibited the lowest IC₅₀ (3.62 μg/mL), with a high selectivity index (SI) of 31.90, despite having the lowest curcuminoid content. While the methanolic extract of <i>Curcuma longa</i> L., known for its high curcuminoid content among <i>Curcuma</i> species, showed an IC₅₀ of 14.83 μg/mL with an SI of 2.80. Further <i>in vitro</i> and <i>in vivo</i> investigations of CKO crude extract are necessary to understand its potential anti-HCoV-OC43 properties.