SARS-CoV-2 is a very well-known and ongoing disaster in humankind. It had devastating effects on people worldwide and for the last three years, humankind had to suffer a consistent fear of death. The day-by-day mutating variants of the virus are increasing the problems of medicinal scientists and researchers. It is the very first known and the globally distributed variant was the Alpha (B.1.1.7 linage) variant [1]. After that, various variants emerged like beta, gamma delta, mu, and many more [2]. These variants mutated and their genome leads to the modulation of the virus. The results of the mutations of these variants are in our sights. Various vaccines were also introduced and a large part of the global population was given vaccines. But the virus is still developing its variants. Recently, in November 2021, Omicron infected cases arrived in South Africa and the World health organization (WHO) declared Omicron as a new variant of COVID-19 [3]. This variant has shown numerous spike-mutations as compared to the other previously known variants [4]. Thus, this variant was named the variant of concern (VOC) by WHO [5]. In a very less time of about two months, this variant has infected at least 108 countries and more than 15 lakh cases have been reported worldwide [6]. Structural changes in the spike-glycoprotein are observed in the Omicron which leads to a large number of mutations in the angiotensin-converting enzyme2 (ACE2) binding sites [7]. Major known mutations of Omicron are SARS-CoV-2501.V2 (B.1.351 lineage), variant B.1.1.529, and VOC 202012/01 (B.1.1.7 lineage) [8]. These variants hold on to mutations of spike protein receptor-binding domain (RBD) that result in the binding of virus proteins to human ACE2 [9]. The study so far claimed the higher binding of Omicron spike-glycoproteins with the ACE2 results in a rise in infection and transmission [10]. However, the high fatality rate of this variant is not recorded so far, but the sustained mutation of this variant may lead to tragic conditions. Thus, drug development is highly needed to terminate this mutation.
On the other hand, herbal extracts had been the frontline warriors throughout the pandemic. People were seen to depend on the herbal aids to revolt against COVID-19. Many homemade remedies for improving the immunity of the body. The literature survey accounts for numerous simulation studies that targeted various variants of COVID-19. Various herbal extracts like I-Asarinin [11], Parthenolide [12], Berberine [13], beta-sitosterol [14], choline [15], etc have been used for inhibiting the proteins of COVID-19.
The Himalayan region is known as the heart of medicinal herbs. Thousands of the varieties of medicinal plants are found in the Himalayan region that holds many medicinal benefits and is known to cure many diseases since Vedic times. One such herbal plant namely, Aconitum Heterophyllum is targeted for this study. This plant is a native of Himalayan foothills, and apart from Uttarakhand, it is also found in Nepal [16]. Regionally, it is named “atish” or “ativisha” and it is a flowering plant [17]. It is found at altitudes between 2,500 m to 4,000 m [18]. This plant has lots of health benefits like they are used as an expectorant, febrifuge, anthelmintic, anti-diarrhoeal, anti-emetic, and anti-inflammatory [19]. The toxicity of the extracts of this plant makes it usable as an anti-poison agent against scorpion or snake bites [20]. Many studies report the use of Aconitum heterophyllum extracts for the treatment of breast cancer [21], artiritis [22], Alzheimer's [23], diarrhea [24], and many more. It is also used to cure fever and contagious diseases which is the main reason to target it as an inhibitor against the COVID-19 variant. As the primary symptom of the Omicron is fever, this is believed that this plant can inhibit the virus and work against its symptoms. This study leads to the identification of a novel phytocompound of Aconitum heterophyllum that can show the inhibitory potentiality against the COVID-19 Omicron variant. The morphology of the plant is illustrated in Fig. 1.
Aconitum heterophyllum has a wide variety of phytochemicals like 14-Anisoylaconine, 6-Acetylheteratisine, 6-Benzoylheteratisine, Aconitine, Atidine, Atisine, Benzoylmesaconine, Dihydroatisine, Heterophyllisine, heterophylloidine, Hetidine, Hetisine, Hetisinone, Isoatisine, Jesaconitine, Lappaconitine, Mesaconitine, Phytosterols, Aricine, beta-carotene, Delphatines, Hypaconitine, lactone atisenol, Lycoctonine, and Veratridie. Molecular docking was performed for all the fifteen phytochemicals and the best-docked ligands were selected. Pharmacokinetic properties of the best-docked ligands were also analyzed to check the proper drug-like behavior. The chemical reactivity of the selected ligand was computed using density functional theory (DFT). The structure optimization was done to fetch the reactivity parameters within the ligand. The Molecular Dynamics (MD) simulation was performed for the best protein-ligand complex to check the stability of the complex. The MD Simulation reveals the stability of the complex and also justifies whether the ligand can be a potential inhibitor or not.