Modeling studies on the role of vitamins B1 (thiamin), B3 (nicotinamide), B6 (pyridoxamine), and caffeine as potential leads for the drug design against COVID-19.

In response to the COVID-19 pandemic, and the lack of effective and safe antivirals against it, we adopted a new approach in which food supplements with vital antiviral characteristics, low toxicity, and fast excretion have been targeted. The structures and chemical properties of the food supplements were compared to the promising antivirals against SARS-COV-2. Our goal was to exploit the food supplements to mimic the topical antivirals' functions but circumventing their severe side effects, which has limited the necessary dosage needed to exhibit the desired antiviral activity. On this line, after a comparative structural analysis of the chemicals mentioned above, and investigation of their potential mechanisms of action, we selected caffeine and some compounds of the vitamin B family and further applied molecular modeling techniques to evaluate their interactions with the RDB domain of the Spike protein of SARS-CoV-2 (SC2Spike) and its corresponding binding site on human ACE-2 (HssACE2). Our results pointed to vitamins B1 and B6 in the neutral form as potential binders to the HssACE2 RDB binding pocket that might be able to impair the SARS-CoV-2 mechanism of cell invasion, qualifying as potential leads for experimental investigation against COVID-19.

Trace determination of lead, chromium and cadmium in herbal medicines using ultrasound-assisted emulsification microextraction combined with graphite furnace atomic absorption spectrometry.

INTRODUCTION: The World Health Organization (WHO) recommends that medicinal plants should be checked for the presence of heavy metals. A preconcentration and separation technique for trace amounts of heavy metals from plant matrix is necessary in order to increase the sensitivity and precision of their determination. OBJECTIVE: Lead, chromium and cadmium contaminations in herbal medicines were monitored using ultrasound-assisted emulsification microextraction (USAEME) combined with graphite furnace atomic absorption spectrometry (GF-AAS). METHODS: In this work, the metal ions in the aqueous solution were complexed with ammonium pyrrolidine dithiocarbamate (APDC) and were extracted into 45 µL of toluene that was sonically dispersed in the aqueous phase. The emulsion formed was centrifuged and 20 µL of separated toluene was injected into a GF-AAS for analysis. Several factors including the kind of extraction solvent and its volume, sample pH, ionic strength and concentration of APDC were optimised. RESULTS: The linear dynamic range (LDR) values were in the range of 0.05 to 20 µg/L and the limit of detection values were in the range of 0.002-0.03 µg/L for target heavy metals. Enrichment factors were obtained in the range of 70-500. The precision of the proposed method was ≤ 8% (n = 5). The obtained amounts of Pb, Cr and Cd in selected herbal medicines were in the standard range, according to the WHO reports. CONCLUSION: The USAEME with GF-AAS procedure was shown to be an efficient, rapid, inexpensive and eco-friendly method for the determination of lead, chromium and cadmium in herbal medicines. Application of the USAEME method leads to an increased extraction efficiency with satisfactory precision in a short time using an extraction solvent volume at the microlitre level.