The antiradical activity of phytol was evaluated by electron paramagnetic resonance towards hydroxyl radical (·OH), superoxide anion radical (·O2(-)), methoxy radical (·CH2OH), carbon-dioxide anion radical (·CO2(-)), as well as towards nitric-oxide radical (·NO) and 2,2-diphenyl-1-picrylhydrazyl (·DPPH) radical. It reduced the production of all tested radicals showing more promising activity against ·CO2(-), ·CH2OH and ·DPPH radicals (56%, 50% and 48%, respectively) in comparison with ·NO, ·O2(-) and ·OH radicals (38%, 23% and 15%, respectively). The antimicrobial activity of phytol was evaluated by the microdilution method against eight bacterial and eight fungal strains. To varying degrees, it was proven to be active against all tested bacteria and fungi (MIC 0.003-0.038 mg/mL and MBC 0.013-0.052 mg/mL, MIC 0.008-0.016 mg/mL and MFC 0.090-0.520 mg/mL, respectively). According to the obtained results, medical foods containing phytol may support development of new therapies for heart disease.

The hydroxyl radical produced in the apoplast has been demonstrated to facilitate cell wall loosening during cell elongation. Cell wall-bound peroxidases (PODs) have been implicated in hydroxyl radical formation. For this mechanism, the apoplast or cell walls should contain the electron donors for (i) H 2 O 2 formation from dioxygen; and (ii) the POD-catalyzed reduction of H 2 O 2 to the hydroxyl radical. The aim of the work was to identify the electron donors in these reactions. In this report, hydroxyl radical (·OH) generation in the cell wall isolated from pea roots was detected in the absence of any exogenous reductants, suggesting that the plant cell wall possesses the capacity to generate ·OH in situ. Distinct POD and Mn-superoxide dismutase (Mn-SOD) isoforms different from other cellular isoforms were shown by native gel electrophoresis to be preferably bound to the cell walls. Electron paramagnetic resonance (EPR) spectroscopy of cell wall isolates containing the spin-trapping reagent, 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N -oxide (DEPMPO), was used for detection of and differentiation between ·OH and the superoxide radical (O 2 -·). The data obtained using POD inhibitors confi rmed that tightly bound cell wall PODs are involved in DEPMPO/OH adduct formation. A decrease in DEPMPO/OH adduct formation in the presence of H 2 O 2 scavengers demonstrated that this hydroxyl radical was derived from H 2 O 2 . During the generation of ·OH, the concentration of quinhydrone structures (as detected by EPR spectroscopy) increased, suggesting that the H 2 O 2 required for the formation of ·OH in isolated cell walls is produced during the reduction of O 2 by hydroxycinnamic acids. Cell wall isolates in which the proteins have been denaturated (including the endogenous POD and SOD) did not produce ·OH. Addition of exogenous H 2 O 2 again induced the production of ·OH, and these were shown to originate from the Fenton reaction with tightly bound metal ions. However, the appearance of the DEPMPO/OOH adduct could also be observed, due to the production of O 2 -· when endogenous SOD has been inactivated. Also, O 2 -· was converted to ·OH in an in vitro horseradish peroxidase (HRP)/H 2 O 2 system to which exogenous SOD has been added. Taken together with the discovery of the cell wall-bound Mn-SOD isoform, these results support the role of such a cell wall-bound SOD in the formation of ·OH jointly with the cell wallbound POD. According to the above fi ndings, it seems that the hydroxycinnamic acids from the cell wall, acting as reductants, contribute to the formation of H 2 O 2 in the presence of O 2 in an autocatalytic manner, and that POD and Mn-SOD coupled together generate ·OH from such H 2 O 2 .

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Plant plasma membranes are known to produce superoxide radicals, while the production of the hydroxyl radical, previously detected in complex plant tissues, is thought to occur in the cell wall. The mechanism of production of superoxide radicals by plant plasma membranes is, however, under dispute. It is shown, using electron paramagnetic resonance spectroscopy with a 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide spin-trap capable of differentiating between radical species, that isolated purified plasma membranes from maize roots produce hydroxyl radicals besides superoxide radicals. The results argue in favour of superoxide production through an oxygen and diphenylene iodonium-sensitive, NADH-dependent superoxide synthase mechanism, as well as through other unidentified mechanism(s). The hydroxyl radical is produced by an oxygen-insensitive, NADH-stimulated mechanism, which is enhanced in membranes in which the superoxide synthase is incapacitated by substrate removal or inhibition.

This review covers the 2003-2012 literature data published for antitumor natural products from marine-derived fungi. The focus is on new and highly potent cytotoxic compounds, together with details related to the relevant fungal species. It describes 22 promising bioactives, originating mainly from symbiotic fungi. The chemical structures of all highlighted organic molecules are briefly discussed.