Violacein and its antifungal activity: comments and potentialities.

Violacein is an important natural antimicrobial pigment that is mainly produced by Chromobacterium violaceum and Janthinobacterium lividum. It presents a significant range of effects against phytopathogenic and human fungi, besides being featured as having low toxicity, and by its important ecological role in protecting amphibian species and applications in dyed medical fabric. The hypothesis about violacein's action mechanisms against mucormycosis (Rhizopus arrhizus) and candidiasis (Candida auris) is herein discussed based on data available in the scientific literature.

Investigation of potential inhibitor properties of violacein against HIV-1 RT and CoV-2 Spike RBD:ACE-2.

A violacein-producing bacterium was isolated from a mud sample collected near a hot spring on Kümbet Plateau in Giresun Province and named the GK strain. According to the phylogenetic tree constructed using 16S rRNA gene sequence analysis, the GK strain was identified and named Janthinobacterium sp. GK. The crude violacein pigments were separated into three different bands on a TLC sheet. Then violacein and deoxyviolacein were purified by vacuum liquid column chromatography and identified by NMR spectroscopy. According to the inhibition studies, the HIV-1 RT inhibition rate of 1 mM violacein from the GK strain was 94.28% and the CoV-2 spike RBD:ACE2 inhibition rate of 2 mM violacein was 53%. In silico studies were conducted to investigate the possible interactions between violacein and deoxyviolacein and three reference molecules with the target proteins: angiotensin-converting enzyme 2 (ACE2), HIV-1 reverse transcriptase, and SARS-CoV-2 spike receptor binding domain. Ligand violacein binds strongly to the receptor ACE2, HIV-1 reverse transcriptase, and SARS-CoV-2 spike receptor binding domain with a binding energy of -9.94 kcal/mol, -9.32 kcal/mol, and -8.27 kcal/mol, respectively. Deoxyviolacein strongly binds to the ACE2, HIV-1 reverse transcriptase, and SARS-CoV-2 spike receptor binding domain with a binding energy of -10.38 kcal/mol, -9.50 kcal/mol, and -8.06 kcal/mol, respectively. According to these data, violacein and deoxyviolacein bind to all the receptors quite effectively. SARS-CoV-2 spike protein and HIV-1-RT inhibition studies with violacein and deoxyviolacein were performed for the first time in the literature.

Violacein-embedded nanofiber filters with antiviral and antibacterial activities.

Most respiratory masks are made of fabrics, which only capture the infectious virus carriers into the matrix. However, these contagious viruses stay active for a long duration (∼7 days) within the fabric matrix possibly inducing post-contact transmissions. Moreover, conventional masks are vulnerable to bacterial growth with prolonged exposure to exhaled breaths. Herein, we combined violacein, a naturally-occurring antimicrobial agent, with porous nanofiber membranes to develop a series of functional filters that autonomously sterilizes viruses and bacteria. The violacein-embedded membrane inactivates viruses within 4 h (99.532 % reduction for influenza and 99.999 % for human coronavirus) and bacteria within 2 h (75.5 % reduction). Besides, its nanofiber structure physically filters out the nanoscale (<0.8 µm) and micron-scale (0.8 µm - 3 µm) particulates, providing high filtration efficiencies (99.7 % and 100 % for PM 1.0 and PM 10, respectively) with long-term stability (for 25 days). In addition, violacein provides additional UV-resistant property, which protects the skin from sunlight. The violacein-embedded membrane not only proved the sterile efficacy of microbe extracted pigments for biomedical products but also provided insights to advance the personal protective equipment (PPE) to fight against contagious pathogens.