1. Introduction

In December 2019, Wuhan, Hubei province, China, became the center of

an outbreak of pneumonia of unknown cause; see Wang et al. (2020). The

emergence of a SARS-like coronavirus (SARS-CoV-2) and its rapid spread

through many countries have been labeled as an international emergency.

The antiviral activity of some metabolites (from the group known as

avonoids) against CoVs is presumed to be caused directly by inhibition of

3C-like protease (3CLpro). In Jo et al. (2020) a avonoid library was used

to systematically probe inhibitory compounds against SARS-CoV 3CLpro.

Rhoifolin, pectolinarin and herbacetin were found to eciently block the enzymatic activity of SARS-CoV 3CLpro. Based on the systematic analysis, the three avonoids were suggested to serve as templates to design functionally improved inhibitors. Simplifying, all coronaviruses produce proteins that have a negative eect on our immune system. Jo et al. (2020)

found that especially three natural plant products, rhoifolin, pectolinarin

and herbacetin, block the activity of these proteins. They attach to active sites of proteins and thereby inactivate them, thus neutralizing the

viruses. All three compounds belong to the group of phenolic structures with

avonoid skeleton, which have many functions in plants; see Decker (1997).

The bioactivity of avonoids may be related to their ability to chelate metals, inhibit lipoxygenase and remove free radicals. In addition, they can act

as free radical scavengers and terminate radical chain reactions that occur

during the oxidation of triglycerides; see Das et al. (1990).

2. Materials and methods

We have conducted bioinformatic meta-analyses of the world's largest

publicly available scientic repository databases: Metabolights

(https://www.ebi.ac.uk/metabolights/) and Prime (http://prime.psc.riken.

jp/menta.cgi/prime/drop_index), as well as scientic publications in which

the described substances have been identied. These datasets contain publicly available metabolic data matrices deposited by scientists and derived

from high-throughput analytical methods, including liquid chromatography coupled with mass spectrometry. The databases were searched with

the keywords rhoifolin, pectolinarin, herbacetin. A set of experiments was

identied for each of the searched phrases. Our analysis concerned experiments in which these pro-health phytochemicals were reported. We found

data matrices for plants known for their high phytochemical activity: barley,

wheat and Brachypodium distachyon from the grass family, as well as thistle, sundew, soybean and Ficus. These plants were selected as plants having

publicly available data that can be used for statistical analysis. Each of

these plants has exactly one of the three considered compounds.

All data sets concerned different types of plant treatment and experimental conditions. Therefore only samples subject to control conditions were selected for analysis. 

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