Application of antifungal metabolites from Streptomyces philanthi RL-1-178 for maize grain coating formulations and their efficacy as biofungicide during storage.

The major safety risk of maize grain is contamination with mycotoxins. In this study, a maize-coating formulation containing freeze-dried culture filtrate of Streptomyces philanthi RL-1-178 (DCF RL-1-178) was developed and evaluated to prevent the growth of mycotoxins during maize grain storage. In vitro studies using confrontation tests on PDA plates indicated that S. philanthi RL-1-178 inhibited the growth of Aspergillus parasiticus TISTR 3276 (89.0%) and A. flavus PSRDC-4 (95.0%). The maize grain coating formulations containing the DCF RL-1-178 (0, 5, 10, and 15% (v/v)) and the polymer polyvinylpyrrolidone (PVP-K90, 4.0% (w/v)) were tested for their efficacy in In vitro and during 5 months storage. In In vitro assay, maize coating formular containing the optimum concentration (15.0%, v/v) of the DCF RL-1-178 exhibited 54.80% and 54.17% inhibition on the growth of A. parasiticus TISTR 3276 and A. flavus PSRDC-4 respectively. The inhibition was also illustrated by the microstructures of interactions between the coated maize grains with or without the DCF RL-1-178 and the fungal pathogens observed under microscope and SEM. Incorporating the DCF RL-1-178 or fungicidal Metalaxyl® into the polymer PVP-K90 maize grains coating resulted in the complete inhibition of the production of aflatoxin B1 (analysed by HPLC) by the two aflatoxigenic pathogens after 5 months storage at room temperature. However, the shelf-life was shortened to only 3 months during storage at room temperature with 90% relative humidity. Overall, the application of the 10-15% DCF RL-1-178 into the maize grain coating formular provides a new alternative measure to control the mycotoxins during storage for at least 5 months. The In vitro cell cytotoxicity study showed that a concentration of 15% (v/v) or 1000 µg/mL of the DCF RL-1-178 had a strong cytotoxic effect on Vero cells. These findings indicate that DCF RL-1-178 is a potential biofungicide for controlling mycotoxins contamination in maize seed storage for planting, but not maize grain storage for animal feed.

Exploring the potential of Crotalaria juncea flower extracts as a source of antioxidants, antimicrobials, and cytoprotective agents for biomedical applications.

Plants provide an unlimited source of bioactive compounds, possessing tremendous applications in the pharmaceutical industry. In the search for sources of antioxidants and antimicrobial agents against human pathogens, ethanol extracts of Crotalaria juncea flowers (CJ flower extract) were evaluated. The highest total phenolic (5.65 µg GAE/ml) and flavonoid (0.43 µg QE/ml) contents were observed in the 100 µg/ml CJ flower extract. To assess antioxidant activity, three in vitro antioxidant tests were employed: DPPH radical-scavenging, ABTS+ radical-scavenging, and hydroxyl radical-scavenging assay. The CJ flower extract demonstrated significant (P < 0.05) antioxidant activity, dependent on the percentage of solvent extraction and the specific assays utilized. The highest antioxidant activity was obtained with 100% ethanol extraction and using the hydroxyl radical-scavenging assay (56.63%). Antimicrobial activity was assessed against six human pathogens, including the fungi Microsporum gypseum and five Gram-positive bacteria (Propionibacterium acnes, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and Streptococcus mutans), as well as one Gram-negative bacterium (Escherichia coli ). The CJ flower extract inhibited the growth of both fungal and bacterial pathogens. The cytotoxicity of the CJ flower extract was measured using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the highest concentration of the extract (100 µg/ml) did not affect L929 cell viability. Moreover, the CJ flower extract demonstrated the ability to suppress H2O2-induced toxicity in L929 cells. Overall, the CJ flower extract has potential as an alternative source for exploring new antioxidants, antimicrobial agents, and cytoprotectants that could prove valuable for biomedical applications.

Efficacy of the antifungal metabolites of Streptomyces philanthi RL-1-178 on aflatoxin degradation with its application to prevent aflatoxigenic fungi in stored maize grains and identification of the bioactive compound.

Aflatoxin B1 is a potent carcinogen produced by Aspergillus flavus (A. flavus) and Aspergillus. parasiticus (A. parasiticus), mainly during grain storage. The efficacy of the freeze-dried culture filtrate of Streptomyces philanthi (S. philanthi) strain RL-1-178 (DCF) on degradation of aflatoxin B1 (AFB1) were evaluated and its bioactive compounds were identified. The DCF at a concentration of 9.0% (w/v) completely inhibited growth and AFB1 production of A. parasiticus TISTR 3276 and A. flavus PSRDC-4 after 7 days tested in yeast-extract sucrose (YES) medium and on stored maize grains after 28 and 14 days incubation, respectively. This indicated the more tolerance of A. parasiticus over A. flavus. The DCF and bacterial cells of S. philanthi were capable to degrade AFB1 by 85.0% and 100% for 72 h and 8 days, respectively. This confirmed the higher efficacy of the DCF over the cells. After separation of the DCF on thin-layer chromatography (TLC) plate by bioautography bioassay, each active band was identified by liquid chromatography-quadrupole time of flight mass spectrometer (LC-Q-TOF MS/MS). The results revealed two compounds which were identified as azithromycin and an unknown based on mass ions of both ESI+ and ESI- modes. The antifungal metabolites in the culture filtrate of S. philanthi were proved to degrade aflatoxin B1. It could be concluded that the DCF may be applied to prevent the growth of the two aflatoxin-producing fungi as well as the occurrence of aflatoxin in the stored maize grains.

In vitro platination of human breast cancer suppressor gene1 (BRCA1) by the anticancer drug carboplatin.

Carboplatin is an anticancer drug for the treatment of cancers affecting various organs including ovary and testes. It essentially exerts its cytotoxicity against cancerous cells via covalent attachment of platinum atom to DNA, generating various platinum-DNA adducts. Platinum-DNA adducts inhibit biological processes essential for cellular viability. However, carboplatin interacts nonspecifically with DNA, resulting in damaging of normal cell DNA. Potential in vitro interaction of carboplatin with genes encoding tumor suppressor proteins such as human breast cancer suppressor gene 1(BRCA1) was herein investigated. The 696--bp fragment of the 3'-region of BRCA1 gene (nucleotide 4897--5592) was amplified by RT-PCR using mRNA templates isolated from human white blood cells. Retardation of the electrophoretic migration on agarose gel of drug-treated DNA, in the dose-response manner, was observed. Analysis by restriction digestion with PvuII and Eco O 109I suggested that the platination favorably occurred at the dGpG sequence of Eco O 109I-cleaved site. The semi-quantitative PCR-based assay was used to determine the lesion frequencies produced by carboplatin in the 696-bp fragment of the 3'-region of BRCA1 gene and in the 3,426-bp fragment of the BRCA1 exon 11 of human breast adenocarcinoma MCF-7 cells. A significant decrease in DNA amplification was observed at 400 microM of carboplatin with approximately 1--2 platinum atoms per BRCA1 fragment. Carboplatin caused slightly less damage at equimolar concentrations in cells than in cell-free BRCA1 fragment.