Discovery of diminazene as a dual inhibitor of SARS-CoV-2 human host proteases TMPRSS2 and furin using cell-based assays.

The proteases TMPRSS2 (transmembrane protease serine 2) and furin are known to play important roles in viral infectivity including systematic COVID-19 infection through priming of the spike protein of SARS-CoV-2 and related viruses. To discover small-molecules capable of inhibiting these host proteases, we established convenient and cost-effective cell-based assays employing Vero cells overexpressing TMPRSS2 and furin. A cell-based proteolytic assay for broad-spectrum protease inhibitors was also established using human prostate cancer cell line LNCaP. Evaluation of camostat, nafamostat, and gabexate in these cell-based assays confirmed their known TMPRSS2 inhibitory activities. Diminazene, a veterinary medicinal agent and a known furin inhibitor was found to inhibit both TMPRSS2 and furin with IC50s of 1.35 and 13.2 µM, respectively. Establishment and the use of cell-based assays for evaluation TMPRSS2 and furin inhibitory activity and implications of dual activity of diminazene vs TMPRSS2 and furin are presented.

Maytenin Plays a Special Role in the Regulation of the Endophytic Bacillus megaterium in Peritassa campestris Adventitious Roots.

Peritassa campestris (Celastraceae) root bark accumulates potent antitumor quinonemethide triterpenes (QMTs). When grown in their natural habitat, plants of the family Celastraceae produce different QMTs such as celastrol (3) and pristimerin (4). However, when they are inserted in in vitro culture systems, they accumulate maytenin (1) as the main compound. Recently, Bacillus megaterium was detected as an endophytic microorganism (EM) living inside P. campestris roots cultured in vitro. We hypothesized that compound (1) controls EM growth more efficiently, and that the presence of EMs in the root culture causes compound (1) to accumulate. For the first time, this work has explored plant-microorganism interaction in a species of the family Celastraceae by co-culture with an EM. Live endophytic bacteria were used, and QMT accumulation in P. campestris adventitious roots was our main focus. The antimicrobial activity of the main QMTs against endophytic B. megaterium was also evaluated. Our results showed that compound (1) and maytenol (5) were more effective than their precursors QMTs (3) and (4) in controlling the EM. Co-culture of B. megaterium with roots significantly reduced bacterial growth whereas root development remained unaffected. Compound (1) production was 24 times higher after 48 hr in the presence of the highest B. megaterium concentration as compared to the control. Therefore, P. campestris adventitious roots affect the development of the endophyte B. megaterium through production of QMTs, which in turn can modulate production of compound (1).

Histochemical investigation of Cochlospermum regium (Schrank) Pilg. leaves and chemical composition of its essential oil.

Essential oil from Cochlospermum regium (Schrank) Pilg. leaves (CR-EO) has been extracted by hydrodistillation; we analysed the CR-EO by gas chromatography coupled with mass spectrometry. We also conducted histochemical analysis on cross-sections of the central vein of young and adult leaves. A total of 32 compounds were qualitatively and quantitatively analysed, which represented 94.87% of the total CR-EO oil content. The CR-EO basically consisted of sesquiterpenes (96.87%); its main component was ß-copaen-4-α-ol (18.73%), followed by viridiflorol (12.67%). The histochemical analyses identified the main classes of compounds present in both young and adult leaves.

Production of the quinone-methide triterpene maytenin by in vitro adventitious roots of Peritassa campestris (Cambess.) A.C.Sm. (Celastraceae) and rapid detection and identification by APCI-IT-MS/MS.

Establishment of adventitious root cultures of Peritassa campestris (Celastraceae) was achieved from seed cotyledons cultured in semisolid Woody Plant Medium (WPM) supplemented with 2% sucrose, 0.01% PVP, and 4.0 mg L⁻¹ IBA. Culture period on accumulation of biomass and quinone-methide triterpene maytenin in adventitious root were investigated. The accumulation of maytenin in these roots was compared with its accumulation in the roots of seedlings grown in a greenhouse (one year old). A rapid detection and identification of maytenin by direct injection into an atmospheric-pressure chemical ionization ion trap tandem mass spectrometer (APCI-IT-MS/MS) were performed without prior chromatographic separation. In vitro, the greatest accumulation of biomass occurred within 60 days of culture. The highest level of maytenin--972.11 µ g·g⁻¹ dry weight--was detected at seven days of cultivation; this value was 5.55-fold higher than that found in the roots of seedlings grown in a greenhouse.

Germinação de sementes in vitro e desenvolvimento de plantas ex vitro de algodãozinho-do-campo / in vitro seeds germination and ex vitro plants development of algodãozinho-do-campo

Este estudo teve por objetivo avaliar a assepsia, quebra de dormência e germinação das sementes de Cochlospermum regium in vitro e o desenvolvimento ex vitro de plantas dessa espécie. Na assepsia das sementes, foram utilizados benlate, hipoclorito de cálcio e ácido sulfúrico. A superação da dormência foi realizada com sementes imersas em ácido sulfúrico por diferentes períodos. Para verificar a influência do tamanho das sementes na germinação, estas foram classificadas em grandes (A=34,08mm²), médias (A=27,74mm²) e pequenas (A=17,99mm²). No desenvolvimento de plantas ex vitro, foram utilizados substratos areia ou solo de Cerrado+esterco. Eficiente assepsia das sementes foi obtida com a utilização do ácido sulfúrico. A imersão por 146 e 144 minutos, para quebra de dormência, proporcionou maior porcentagem de germinação (63 por cento) e IVG (0,78) respectivamente - sem nenhuma contaminação. As sementes maiores apresentam maior IVG (0,61) em relação a sementes menores. Embora o desenvolvimento das plantas em solo de Cerrado+esterco ou areia tenha sido semelhante, no primeiro substrato, as mudas mostraram-se mais vigorosas.

This study was designed to conduct experiments with germination and dormancy breaking in in vitro seeds of Cochlospermum regium in vitro and evaluate the development of plants ex vitro for this species. For the sterilization of seeds introduced in vitro, were used benlate, calcium hypochlorite and sulfuric acid. The break dormancy was realized with seeds immersed in sulfuric acid for different periods. To check the influence of seed size on germination, they were classified as large (A=34.08mm²), medium (A=27.74mm²) and small (A=17.99mm²). For the development of ex vitro plants were used sand substrate or Cerrado soil + manure. Efficient sterilization of seeds was achieved with the use of sulfuric acid. The immersion for 146 and 144 minutes, to break dormancy, showed higher germination rate and germination speed of 63 percent and 0,78 respectively - with no contamination. Larger seeds germinated faster (0.61) than smaller ones. Though ex vitro development of plants cultured in both substrates was similar, plantlets cultured in soil + manure were more vigorous.