Chromatographic separation of extracts from the fungal biomass of a plant pathogenic fungus, Myrothecium roridum, yielded 8 trichothecene toxins including 6 type D trichothecenes (1–6) and 2 type A trichothecenes (7–8). 6′,12′-Epoxymyrotoxin A (1) and 7′-hydroxymytoxin B (2) were new macrocyclic trichothecenes, while the other trichothecenes were identified as myrotoxin B (3), myrotoxin D hydrate (4), 2′,3′-epoxymyrothecine A (5), miotoxin A (6), and 2 trichothecenes lacking the macrocyclic lactone system, roridin L-2 (7) and trichoverritone (8). The structures of these mycotoxins were characterized using spectroscopic methods. The absolute configurations of 1 and 2 were determined by NOESY and a comparison of their experimental and calculated ECD spectra. Most of these mycotoxins (1–4 and 6) exhibited highly potent antimalarial activity against Plasmodium falciparum. They also showed strong cytotoxicity towards KB and NCI-H187 cell lines (IC50 0.60 – 112.28 nM), as well as the Vero cell line (IC50 1.50 – 46.51 nM).
Essential parameters related to the photoelectrochemical properties, such as ground state geometries, electronic structures, oxidation potential and electron driving force, of cochineal insect dyes were investigated by DFT and TDDFT at the B3LYP/6-31+G(d,p) level of the theory. The results show that the major charge flow dynamic for all dyes is the HOMO→LUMO transition. The bi-coordinated binding mode, in which the dye uses one carboxyl- and hydroxyl oxygen bound to Ti(IV), is found for all dye-TiO(2) systems. Additionally, the doubly bi-coordinated binding mode in which the dye used both carboxyl groups bound to two Ti(IV) is also possible due to high energy distribution occupied at anchoring groups. This study highlights that most of these insect dyes can be good photosensitizers in dye-sensitized solar cells based on their strong binding to the TiO(2) surface, good computed excited state oxidation potential and thermodynamically favored electron driving force.
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