Synthesis and anti-SARS-CoV-2 activity of amino acid modified cephalotaxine derivatives.

The severe acute respiratory syndrome coronavirus (SARS-CoV-2) pandemic has triggered a significant impact on global public health security, it is urgent to develop effective antiviral drugs. Previous studies have found that binding to ACE2 is a key step in the invasion of SARS-CoV-2 into host cells, so virus invasion can be inhibited by blocking ACE2, but there are few reports on this kind of specific inhibitor. Our previous study found that Harringtonine (HT) can inhibit the entry of SARS-CoV-2 spike pseudovirus into ACE2h cells, but its relatively high cytotoxicity limits its further development. Amino acid modification of the active components can increase their solubility and reduce their cytotoxicity. Therefore, in this study, seven new derivatives were synthesized by amino acid modification of its core structure Cephalotaxine. The target compounds were evaluated by cell viability assay and the SARS-CoV-2 spike pseudovirus entry assay. Compound CET-1 significantly inhibited the entry of pseudovirus into ACE2h cells and showed less cytotoxicity than HT. Molecular docking results showed that CET-1 could bind TYR83, an important residue of ACE2, just like HT. In conclusion, our study provided a novel compound with more potential activity and lower toxicity than HT on inhibiting the SARS-CoV-2 spike pseudovirus infection, which makes it possible to be a lead compound as an antiviral drug in the future.

HPLC-fluorescence detection for stability of harringtonine, and identification of degradation products by UPLC-Q-TOF-MS.

Harringtonine (HT) is an anticancer alkaloid early extracted and isolated from cephalotaxus fortunei Hook. f., also has various pharmacological activities such as antiviral, antibacterial, antimalarial, anti-inflammatory, antioxidant, herbicidal and insecticidal. However, the factors affecting the stability of HT, the main degradation sites and mechanisms involved in its disposal process in vivo have not yet been elucidated. This study utilized HPLC-fluorescence detection method to establish a simple quantitative detection method for HT with good accuracy, precision, and high sensitivity. Temperature and pH were the main factors affecting the stability of HT, which underwent significant degradation in high temperature and alkaline environments because of the occurrence of hydrolysis reactions. In isolated biological homogenates of SD rats, except gastrointestinal tract, HT was degraded in other sites, especially respiratory, mainly in airway and lungs, and systemic metabolism, mainly in livers, spleens, and kidneys. Through UPLC-Q-TOF-MS, three forced degradation products were identified as 4'-demethyl HT, cephalotaxine, and dehydrated HT, respectively. However, the degradation product in isolated biological homogenates of SD rats was only 4'-demethyl HT due to the relatively mild environment. Our findings contributed to a necessary study basis for HT in terms of structural optimization, dosage form selection, storage and transportation.