Background The current health concern to the entire world is the chronic respiratory disease caused by coronavirus 2 (COVID-19). A specific treatment or proper therapy is still lacking, and the investigations from across the world for proper drug/vaccine development towards disease control are in progress. The Coronavirus replication takes place by the conversion of the polypeptide into functional protein and this occurs due to the key enzyme Main protease (M pro ). Therefore, identification of natural and effective M pro inhibitors could be a safe and promising approach for COVID-19 control. Methods The present in silico study evaluates the effect of bioactive compounds found in Eucalyptus and Corymbia species essential oil on M pro by docking. Molecular docking of the major seven compounds of essential oil (citronellol, alpha-terpineol, eucalyptol, d -limonene, 3-carene, o -cymene, and alpha-pinene) with M pro was studied by AutoDock 4.2, and the properties were analysed by PreADMET and Biovia Discovery Studio visualizer. Results The calculated parameters such as binding energy, hydrophobic interactions, and hydrogen bond interactions of 6LU7 (M pro ) with Eucalyptus and Corymbia volatile secondary metabolites represented its scope as an effective therapy option against covid-19. Among the docked compounds, eucalyptol shows the least binding energy without toxicity. Conclusions The outcome of this study reported that the essential oil of Eucalyptus and Corymbia species, mainly eucalyptol can be utilized as a potential inhibitor against COVID-19 and also it can be used in its treatment. Hence, further analysis was required to explore its potential application in medicine.

Coringa mangrove forest is located in the Godavari delta, Andhra Pradesh, India. The mangrove community consisted of more than 13 species of mangrove and other plants in the present study area. The following three dominant mangrove plants, Avicennia marina, Excoecaria agallocha and Sonneratia apetala were found to be present on the banks of a major channel of the Godavari river running through the forest. The structure and species distribution of mangrove, in the Channel Nagathana Kalava has been described. The area behind the belt consisting of Acanthus ilicifolius and Myriostachya wightiana is generally colonized by E. agallocha and A. marina. The zone has been called the Avicennia and Excoecaria zone. Adjacent to this zone species like Aegiceras corniculatum and A. oficinalis were the common species. In the flat clayey soil, Suaeda maritima was found to grow. In areas of high elevation, devoid of inundation of tidal seawater during the high tidal period, species such as M. wightiana and Acanthus were found to colonize both the banks of the channels.

Muthupet mangrove ecosystem (loo 25' N and 79" 30' E) is located at the southern end of the Cauvery delta on the east coast of India. The swamp is characterized by the presence of only 4 species of exclusive mangroves namely Avicennia marina, Excoecaria agallocha, Aegiceras corniculatum and Acanthus ilicifolius.Community structure analysis carried out at four randomly selected quadrats showed that the relative density, relative dominance, relative frequency and importance value of A. marina was relatively higher than for the other three species. Hence, Muthupet mangrove ecosystem is characterized by the mono-specific dominance ofA. marina. Earlier palynological studies indicate that species like Rhizophora were present in this swamp some 200 years ago. It is believed that the past management practices together with the present poor scientific policy of the decision makers and harsh environment conditions may be considered as a few factors responsible for the disappearance of Rhizophora from this mangrove swamp.

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