Antifungal and antioxidant effects of phenolic acids and flavonol glycosides from Tetraclinis articulata

The present study investigated the crossing of extraction solvent with vegetative stage of Tetraclinis articulata to result in an extract having a strong antifungal and antioxidant activities. Results showed that dichloromethane extract at vegetative stage were the most active to inhibit Botrytis cinerea mycelial growth and conidia germination. The identification by HPLC-MSn of active extract revealed that phenolic acids (sandaracopimaric, communic, and cupressic acids) were responsible for antifungal activity. However, methanol and fructification stage were the best solvent and phonological stage to extract bioactive compounds with antioxidant activity. This methanolic extract from fructification stage was also characterized by the highest contents of polyphenols and flavonoids. According to HPLC-MSn, flavonol glycosides (myricetin 3-O-rhamnoside, quercetin-7-O-rhamnoside, quercetin-7-O-rutinoside, and trimeric form of kaempferol) were responsible for antioxidant activity of T. articulata. Consequently, T. articulata extracts could be used as an alternative to chemical pesticides for the treatment of grey mould disease and oxidative stress

Fragment orbital based description of charge transfer in peptides including backbone orbitals

Charge transfer in peptides and proteins can occur on different pathways, depending on the energetic landscape as well as the coupling between the involved orbitals. Since details of the mechanism and pathways are difficult to access experimentally, different modeling strategies have been successfully applied to study these processes in the past. These can be based on a simple empirical pathway model, efficient tight binding type atomic orbital Hamiltonians or ab initio and density functional calculations. An interesting strategy, which allows an efficient calculations of charge transfer parameters, is based on a fragmentation of the system into functional units. While this works well for systems like DNA, where the charge transfer pathway is naturally divided into distinct molecular fragments, this is less obvious for charge transfer along peptide and protein backbones. In this work, we develop and access a strategy for an effective fragmentation approach, which allows one to compute electronic couplings for large systems along nanosecond time scale molecular dynamics trajectories. The new methodology is applied to a solvated peptide, for which charge transfer properties have been studied recently using an empirical pathway model. As could be expected, dynamical effects turn out to be important, which emphasizes the importance of using effective quantum approaches which allow for sufficient sampling. However, the computed rates are orders of magnitude smaller than experimentally determined, which indicates the shortcomings of present modeling approaches