Medicinal Plants against Viral Infections: A Review of Metabolomics Evidence for the Antiviral Properties and Potentials in Plant Sources

Most plants have developed unique mechanisms to cope with harsh environmental conditions to compensate for their lack of mobility. A key part of their coping mechanisms is the synthesis of secondary metabolites. In addition to their role in plants' defense against pathogens, they also possess therapeutic properties against diseases, and their use by humans predates written history. Viruses are a unique class of submicroscopic agents, incapable of independent existence outside a living host. Pathogenic viruses continue to pose a significant threat to global health, leading to innumerable fatalities on a yearly basis. The use of medicinal plants as a natural source of antiviral agents has been widely reported in literature in the past decades. Metabolomics is a powerful research tool for the identification of plant metabolites with antiviral potentials. It can be used to isolate compounds with antiviral capacities in plants and study the biosynthetic pathways involved in viral disease progression. This review discusses the use of medicinal plants as antiviral agents, with a special focus on the metabolomics evidence supporting their efficacy. Suggestions are made for the optimization of various metabolomics methods of characterizing the bioactive compounds in plants and subsequently understanding the mechanisms of their operation.

Tea Harvesting and Processing Techniques and Its Effect on Phytochemical Profile and Final Quality of Black Tea: A Review

Tea (Camellia sinensis) has grown for over 300 years and is recognized worldwide as among other well-renowned crops. The quality of black tea depends on plucking (method, standard, season, and intervals), withering and rolling (time and temperature), fermentation (time, temperature, and RH), drying (temperature and method), and storage conditions, which have a high influence on the final quality of black tea. At the rolling stage, the oxidation process is initiated and ends at the early drying stage until the enzymes that transform tea polyphenols into thearubigins (TRs) and theaflavins (TFs) are denatured by heat. By increasing fermentation time, TRs increased, and TF decreased. Each is liable for black tea's brightness, taste, and color. The amino acids and essential oils also grant a distinctive taste and aroma to black tea. Throughout withering, rolling, and fermentation, increases were found in essential oil content, but during drying, a decrease was observed. However, the Maillard reaction, which occurs when amino acids react with sugar during drying, reimburses for this decrease and enhances the flavor and color of black tea. As compared to normal conditions, accelerated storage showed a slight decrease in the total color, TF, and TRs. It is concluded that including plucking, each processing step (adopted technique) and storage system has a remarkable impact on black tea's final quality. To maintain the quality, an advanced mechanism is needed to optimize such factors to produce high-quality black tea, and an objective setting technique should be devised to attain the desirable quality characteristics.

Antiviral Potential of Plants against COVID-19 during Outbreaks-An Update

Several human diseases are caused by viruses, including cancer, Type I diabetes, Alzheimer's disease, and hepatocellular carcinoma. In the past, people have suffered greatly from viral diseases such as polio, mumps, measles, dengue fever, SARS, MERS, AIDS, chikungunya fever, encephalitis, and influenza. Recently, COVID-19 has become a pandemic in most parts of the world. Although vaccines are available to fight the infection, their safety and clinical trial data are still questionable. Social distancing, isolation, the use of sanitizer, and personal productive strategies have been implemented to prevent the spread of the virus. Moreover, the search for a potential therapeutic molecule is ongoing. Based on experiences with outbreaks of SARS and MERS, many research studies reveal the potential of medicinal herbs/plants or chemical compounds extracted from them to counteract the effects of these viral diseases. COVID-19's current status includes a decrease in infection rates as a result of large-scale vaccination program implementation by several countries. But it is still very close and needs to boost people's natural immunity in a cost-effective way through phytomedicines because many underdeveloped countries do not have their own vaccination facilities. In this article, phytomedicines as plant parts or plant-derived metabolites that can affect the entry of a virus or its infectiousness inside hosts are described. Finally, it is concluded that the therapeutic potential of medicinal plants must be analyzed and evaluated entirely in the control of COVID-19 in cases of uncontrollable SARS infection.

Entry-inhibitory role of catechins against SARS-CoV-2 and its UK variant

BACKGROUND

The global pandemic caused by a RNA virus capable of infecting humans and animals, has resulted in millions of deaths worldwide. Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) infects the lungs, and the gastrointestinal tract to some extent. Rapid structural mutations have increased the virulence and infectivity of the virus drastically. One such mutated strain known as the UK variant has caused many deaths in the United Kingdom.

HYPOTHESIS

Among several indigenous natural ingredients used for prevention and cure of many diseases, the catechins have been reported for their antiviral activity, even against SARS-CoV-2. Characteristic mutations present on the spike protein have presented the newer strain its enhanced infectivity. The spike protein helps the virus bind to ACE2 receptor of the host cell and hence is a drug target. Catechins have been reported for their entry-inhibitory activity against several viruses.

METHOD

In this study, we performed molecular docking of different catechins with the wild and mutant variants of the spike protein of SARS-CoV-2. The stability of the best docked complexes was validated using molecular dynamics simulation.

RESULTS

The in-silico studies show that the catechins form favourable interactions with the spike protein and can potentially impair its function. Epigallocatechin gallate (EGCG) showed the best binding among the catechins against both the strains. Both the protein-ligand complexes were stable throughout the simulation time frame.

CONCLUSION

The outcomes should encourage further exploration of the antiviral activity of EGCG against SARS-CoV-2 and its variants.

Validated HPTLC and antioxidant activities for quality control of catechin in a fermented tea (Camellia sinensis var. assamica)

Miang, a Thai traditional fermented tea (Camellia sinensis var. assamica), is exploited as nutraceutical and cosmeceutical ingredients despite limited standardization studies. Thus, this research aimed to develop a simple and rapid method for miang quality control using catechin and high-performance thin-layer chromatography (HPTLC) validated according to the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) and the Association of Official Analytical Collaboration (AOAC). The developing solvent consisting of toluene: ethyl acetate: acetone: formic acid (6:6:6:1 v/v/v/v) showed acceptable specificity with R f value of 0.54 ± 0.02 and linearity with correlation coefficient of 0.9951. The recovery was 98.84%-103.53%, and the RSD of intra- and inter-day precision was 0.70%-3.00% and 1.93%-4.94%, respectively. Miang ethyl acetate fraction is suggested to be attractive ingredient due to rich catechin (25.78 ± 0.53%), prolonged stability at 40 ◦C, and strong antioxidants determined by the assays of ABTS (IC50 = 3.32 ± 0.74 mg/ml), FRAP (89.05 ± 15.49 mg equivalent of FeSO4/g), and inhibition of lipid peroxidation (IC50 = 4.36 ± 0.67 mg/ml).