Floral attractants in the black orchid Brasiliorchis schunkeana (Orchidaceae, Maxillariinae): clues for presumed sapromyophily and potential antimicrobial activity.

BACKGROUND: Orchids have evolved various strategies that aim to ensure their reproduction success. These may include the production of rewards for pollinators, or on the contrary, deception. Specific sets of features such as flower morphology, color, nectar, and odor presence (or lack thereof) are considered to determine suitability for pollination by different groups of animals. Stingless bees are thought to be the primary pollinators of the orchids of the Neotropical subtribe Maxillariinae. However, almost black flowered Brasiliorchis schunkeana at first glance presents floral adaptations that may suggest another pollination syndrome-sapromyophily. RESULTS: A few traces of secretion were noticed on the glabrous lip callus and lip apex built by conical to villiform papillae (SEM analysis). Histochemical studies revealed huge amounts of lipids in the epidermis, subepidermis, and some parenchyma cells (SBB test) with various stages of lipids accumulation between cells. Further TEM analysis showed a heterogeneous (lipoid and phenolic) nature of secretion. The dense osmiophilic cytoplasm contained organelles (RER, free ribosomes, dictyosomes, plastids with plastoglobuli, nucleus) and vesicles migrating to plasmalemma. The vesicles, osmiophilic globules, and flocculent material were visible in periplasmic space. The central vacuole possessed osmiophilic phenolic content and flocculent material. GC-MS analysis revealed in floral extract the presence of 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione (77.06%) and 2,5-di-tert-butyl-1,4-benzoquinone (16.65%). Both compounds are known for their biological activity. CONCLUSIONS: The juxtaposition of results led us to the conclusion that the labellar tissue produces lipoid and phenolic material, which is responsible for the glossiness and rotten herring scent. This type of secretion could be classified as a phenolic resin. The chemical analysis revealed the presence of five semiochemicals that are known to be attractants for some Diptera, which together with the rest of the results constitutes a strong premise that representatives of this order could be potential pollinators of B. schunkeana. Field observations however are still needed to confirm this pollination syndrome.

Identification and assessment of residual levels of the main oxidation product of tert-butylhydroquinone in frying oils after heating and its cytotoxicity to RAW 264.7 cells.

tert-Butylhydroquinone (TBHQ) losses and the residual levels of 2-tert-butyl-1,4-benzoquinone (TBBQ) in tripalmitin at different heating temperatures with or without reflux over various time intervals were investigated. Heating at 120 °C resulted in the slowest TBHQ loss and the highest TBBQ levels (52.61-62.93 µg/mL). The highest TBBQ concentrations (111.73-164.67 µg/mL) at 5 and 8 h and residual concentrations of 10.23-46.95 µg/mL during heating at 170 °C over 24 h were observed. Furthermore, the potential cytotoxicity of TBBQ to RAW 264.7 cells was evaluated with the MTT assay, Hoechst 33258 staining test, and flow cytometry analysis. Results indicate that TBBQ dose- and time-dependently decreased the growth of cells and inhibited DNA synthesis by regulating the S/G2 transition. The TBBQ concentration giving 50% inhibition in RAW 264.7 cells was 10.71 µg/mL. This threshold value is lower than the residual level of TBBQ in oil, indicating the necessity for concerns over the safety of fried food in terms of TBBQ residues.

Preclinical evaluation and molecular docking of 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ) from Streptomyces sp. VITVSK1 as a potent antibacterial agent.

The incidence of bacterial disease has increased tremendously in the last decade, because of the emergence of drug resistance strains within the bacterial pathogens. The present study was to investigate the antibacterial compound 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ) isolated from marine Streptomyces sp. VITVSK1 as a potent antibacterial agent. The antibacterial potential of DTBBQ was investigated against RNA Polymerase (PDB ID-1I6V) by in silico molecular docking tools. Results of our study showed the high affinity interaction between DTBBQ and RNA polymerase and also confirmed the drug likeliness of DTBBQ using ADMET in silico pharmacology tools. Our findings suggest that DTBBQ could be used as antibacterial drug to defend the emerging antibacterial resistance.