Photoprotection of Wood Surfaces by Wood-Ion Complexes

Mechanisms for protection of wood surfaces against weathering imparted by metal ions of inorganic salts, namely ferric ions and chromium ions, were elucidated. The lignin model compounds study revealed that the effectiveness of weathering protection is likely due to formation of complex between wood components and ferric chloride as well as chromium trioxide, which induced energy transfer to provide protection. The complex formation between lignin model compounds and metal ions was confirmed by the analyses of their infrared spectra, ultraviolet-visible spectra, and nuclear magnetic resonance spectra. These findings revealed that guaiacol and catechol reacted with metal ions to form water-insoluble complexes. Although cellobiose-ion complex was not isolated, it was evident by IR study that cellobiose participated in complex formation and accelerated the rate of complex formation. Like model compounds, it is plausible that wood-ion complexes being formed at the wood surfaces effectively blocked the free phenolic hydroxy groups, which are the reactive centers to initiate photochemical reactions, and thereby provided photoresistance to wood surfaces. It is likely that the complex systems are capable of minimizing photochemical reactions by energy transfer from wood to wood complexes, to emit effective energy harmlessly from wood surfaces. In addition, it is possible that wood-ion complexes might decompose peroxide impurities formed at wood surfaces to avoid photodegradation chain reactions

Photodegradation and Photoprotection of Wood Surfaces

Photodegradation of southern yellow pine and its protection have been studied. Scanning electron micrographs showed that most of the cell walls on exposed transverse surfaces were separated at the middle lamella region after only 500 h of ultraviolet light irradiation. Fibers at the surface were degraded severely after 1,000 h of irradiation. Half-bordered pits and bordered pits on exposed radial surfaces were severely damaged by ultraviolet light. Enlargement of pit apertures as well as loss of pit domes was observed. However, wood irradiated on tangential surfaces was quite resistant to UV irradiation; only microchecks were observed. The photodegradative effect on wood surfaces can be mitigated by treating with aqueous solutions of chromic acid or ferric chloride. Only relatively small amounts of these chemicals are needed for effective protection. Possible chemistry and mechanisms of degradation and protection are discussed

Activity of Cinnamomum Osmophloeum Leaf Essential Oil Against Anopheles gambiae s.s

The increasing status of insecticide resistant mosquitoes in sub-Saharan Africa is a threatening alert to the existing control efforts. All sibling species of An. gambiae complex have evolved insecticide resistance in wild populations for different approved classes of the insecticides currently in use in the field. An alternative compound for vector control is absolutely urgently needed. In this study, the larvicidal activity and chemical composition of the Cinnamomum osmophloeum leaf essential oils were investigated. C. osmophloeum leaf essential oils were extracted by hydrodistillation in a Clevenger-type apparatus for 6 hours, and their chemical compositions identified using GC-MS. These oils were evaluated against An. gambiae s.s. in both laboratory and semi-field situations. The WHO test procedures for monitoring larvicidal efficacy in malaria vectors were used. The composition of C. osmophloeum leaf essential oil has been found to have 11 active compounds. The most abundant compound was trans-cinnamaldehyde (70.20%) and the least abundant was caryophyllene oxide (0.08%). The larvicidal activity was found to be dosage and time dependant both in laboratory and semi-field environments with mortality ranging from 0% to 100%. The LC50 value was found to vary from 22.18 to 58.15 µg/ml in the laboratory while in semi-field environments it was 11.91 to 63.63 µg/ml. The LC90 value was found to range between 57.71 to 91.54 µg/ml in the laboratory while in semi-field environments was 52.07 to 173.77 µg/ml. Mortality ranged from 13% to 100% in the laboratory while in semi-field environments it ranged between 43% to 100% within mortality recording time intervals of 12, 24, 48, and 72 hours. The larvicidal activity shown by C. osmophloeum leaf essential oil is a promising alternative to existing larvicides or to be incorporated in integrated larval source management compounds for An. gambiae s.s control. The efficacy observed in this study is attributed to both major and minor compounds of the essential oils. \u