Propolis is a multi-functional bee product rich in polyphenols. In this study, the inhibitory effect of Anatolian propolis against SARS-coronavirus-2 (SARS-CoV-2) was investigated in vitro and in silico. Raw and commercial propolis samples were used, and both samples were found to be rich in caffeic acid, p-coumaric acid, ferulic acid, t-cinnamic acid, hesperetin, chrysin, pinocembrin, and caffeic acid phenethyl ester (CAPE) at HPLC-UV analysis. Ethanolic propolis extracts (EPE) were used in the ELISA screening test against the spike S1 protein (SARS-CoV-2): ACE-2 interaction for in vitro study. The binding energy values of these polyphenols to the SARS-CoV-2 spike and ACE-2 protein were calculated separately with a molecular docking study using the AutoDock 4.2.6 program. In addition, the pharmacokinetics and drug-likeness properties of these eight polyphenols were calculated according to the SwissADME tool. The binding energy value of pinocembrin was highest in both receptors, followed by chrysin, CAPE, and hesperetin. Based on the in silico modeling and ADME (absorption, distribution, metabolism, and excretion) behaviors of the eight polyphenols, the compounds exhibited the potential ability to act effectively as novel drugs. The findings of both studies showed that propolis has a high inhibitory potential against the Covid-19 virus. However, further studies are now needed.

The inhibitory effects of Anatolian propolis were investigated against Human Immunodeficiency Virus type-1 reverse transcriptase (HIV-1 RT). The aim of the study was to assess the antiviral properties of the water-soluble propolis extract and to identify naturally occurring inhibitors within this type of propolis, with a specific focus on compounds demonstrating non-cytotoxic antiviral activity. To accomplish this, propolis extract’s antioxidant capacities (FRAP), radical scavenging activities, total flavonoids (TFC), and phenolic contents (TPC) were determined and found to be 1088.67 ± 43.30 (μmol FeSO₄∙7H₂O/g), 3.19 ± 0.11 mg/mL, 1.05 ± 0.1 (mg QE/g) and 56.31 ± 0.40 mg GAE/g), respectively. The content of the 2-kDa filtrate of extract was identified by the Orbitrap LC-MS, RP-HPLC-UV, HPLC-DAD. HIV-1 RT inhibition assays were performed for identified phenolic compounds, with dioxygen antibody for colorimetric detection and IC₅₀ values were determined against HIV-1 RT. The compounds (pinocembrin, luteolin, myricetin, quercetin, tannic acid, fisetin) with IC₅₀ values below 1 mM have shown a generally synergistic inhibitory effect in their binary combinations at IC₅₀ concentrations. Their combination exhibited an inhibitory effect equivalent to that in positive control presented by Nevirapine. The cytotoxic effects of the most effective 6 phenolic compounds were determined on Jurkat cells by 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide assay. This observation suggests that these compounds are suitable and promising candidates as potential raw materials for the development of anti-HIV-1 drugs.

The molecules that consist of propolis are generally polyphenols, and they have many activities such as antiviral, antibacterial and antifungal activities. In this study, it is aimed to investigate the inhibiting capacity of the interaction between ACE-2 and Spike RBS by propolis samples belong to three different cities (Trabzon, Kocaeli, Kırıkkkale). After determining the propolis sample exhibiting the highest inhibition effect, the phenolics within this sample were identified, individual assessments of the inhibition effects of each phenolic compound were conducted with Spike S1 (SARS-CoV-2): ACE2 Inhibitor Screening Colorimetric Assay Kit and supported by docking studies in silico. Propolis sample with the highest inhibition effect was determined as 'Kocaeli'. Then, the pure molecules known to be present in Kocaeli propolis were tested and found that p-OH benzoic acid, syringic acid, ferulic acid and gallic acid did not have any inhibitory effects on the Spike S1 (SARS-CoV-2): ACE2 interaction. The substances with the greatest inhibitory effect are; protocathecuic acid, caffeic acid, p-coumaric acid with the inhibition of 62.29%, 58.34%, 59.20%, respectively. The lowest IC50 value of the flavonoids was found to be 0.89 mM with caffeic acid. Over all in silico, in vitro experiments, and MTT analyses conducted in the literature have demonstrated that caffeic acid and protocatechuic acid can be used as a highly active compound against COVID-19.

In this study, esterase of Aneurinibacillus sp. PDF24 strain, a thermophilic bacteria, was purified to homogenity (5.25 fold purification) by column chromotography, and characterized. The molecular weight of Aneurinibacillus sp. PDF24 esterase was determined about 40 kDa. The maximum activity of the purified esterase was analyzed at 55°C, pH 8.5. The esterase was found to be stable at 40ºC, 50ºC and 60ºC for 1 hour. Km and Vmax values for p-nitrophenyl butyrate were determined as 0.120 mM and 3164.8 U/mg, respectively. Considering Km values in the literature, Aneurinibacillus sp. PDF24 esterase was found to have a good Km value compared to other esterases. In the presence of 1 mM and 5 mM metal salts of Mg2+, Li+, Ca2+, K+, no significant change occured in enzyme activity. The activity of Aneurinibacillus sp PDF24 esterase was found to be stable also in the presence of ethanol, DMSO, EDTA, DTT and ß-mercaptoethanol. The data obtained suggest that the enzyme is a serine esterase, not a metalloprotein, and that disulfide bonds are not required to maintain enzyme conformation, and therefore, depending on its features, this esterase may be a suitable candidate for industrial applications.