Research progress of effect and mechanism of 1,8-Cineole on IBV
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1,8-Cineole is the main component of eucalyptus oil, which has antibacterial, anti-inflammatory,and parasite repellent effects. At present, it is widely used in medicine, food, daily chemical and other fields. In the field of medicine, it is mainlyused in the treatment of influenza, colds, bacillary dysentery, enteritis andvarious infections (including mumps, meningitis, suppurative tonsillitis,pediatric head ulcers, erysipelas, trauma infections), etc. At present, thereare many researches on the mechanism of antibacterial, anti-inflammatory and deworming, but not many researches on the role of anti-virus.
Avian infectiousbronchitis (IB) is a highly contagious infectious disease caused by infectiousbronchitis virus (IBV). IBV-infected chickens are mainly characterized bypathological changes in the respiratory tract, kidney and reproductive system.IB is widespread worldwide, causing great economic losses, and is one of themost serious diseases that endanger the poultry breeding industry. IBV iscurrently mainly prevented by attenuated vaccines or inactivated vaccines.
However, due to the large number of IBV serotypes, there is a lack of effectivecross-protection between different serotypes, and new variant strains continueto appear, which brings great chanllenge to the diagnosis and prevention ofthis disease.
IBV belongs to thefamily of coronaviruses. It has a spherical structure and is a single-strandedRNA virus with an envelope. The genome consists of structural proteins andnon-structural proteins. The structural proteins of IBV are composed of spikeprotein (S), membrane protein (Membrane, M), small envelope protein(Smallenvelope, E) and Nucleocapsid (Nucleocapsid, N). The structural proteinis used in virus adsorption, replication and the transcription process plays arole. The non-structural proteins of IBV are two polyproteins, PP1a and PP1b.These two polyproteins are cleaved into 16 functional proteins nsp1-16 by theprotease encoded by IBV in the body. Changes in the functions of thesenon-structural proteins will affect the evolution of IBV.
Figure 1 IBV virus structure
Research on1,8-cineole in anti-IBV, Wu Nan et al. (2008) studied the mechanism of1,8-cineole against IBV at the cellular and molecular level, and the resultsshowed that: 1,8-cineole has the inhibitory effect of IBV is mainly reflectedin the direct inactivation effect. It also has a certain effect in the IBVadsorption and replication stage. In addition, its mechanism of action is thatthe receptor binding site of 1,8-cineole has a strong effect on the N protein.Inhibit the replication and assembly of the virus.
Zhiwei Yang et al.(2010) also proved that 1,8-cineole's anti-IBV activity is the main mechanismof action. The binding site of 1,8-cineole is located at the N-terminus ofphosphorylated nucleocapsid (N) protein. And through MTT analysis, it showedthat the inhibitory effect of 1,8-cineole on IBV occurred moderately beforeentering the cell, and was significantly stronger after the virus penetratedinto the cell. It also compared the effect of ribavirin against IBV.
The results showedthat the CC50 (50% cytotoxic concentration) of 1,8-cineole was higher than10mM, while the CC50 of ribavirin was 1mM. The maximum TD0 (non-cytotoxicconcentration) of 1,8-cineole was determined to be 3.90±0.22mM, much higherthan ribavirin (0.78±0.15mM). 1,8-Cineole can inhibit IBV with an IC50 (50%viral inhibitory concentration) of 0.61mM.