Hops have been used in the brewing of alcoholic beverage for over 3000 years. Due to new consumer preferences towards sweeter drinks or 'Alcopops', beer consumption has taken a drastic decline. This has caused the economic value of hops as a commodity to decline, therefore new applications for this material are required. The hop extracts humulone (8) and lupulone (22) exist in several tautomeric forms. We present unequivocal evidence for the existence of the major tautomer of lupulone, colupulone and a derivative of humulone in polar media. The evidence has been obtained from single X-ray crystallographic data and computer modelling as well as IH and 13e NMR spectroscopy. The first 2D INADEQUATE spectrum of the tautomer of lupulone provides unambiguous chemical shift assignments for all of the structural carbon atoms. This project has also involved the investigation into known and novel derivatives of the major constituents of hops, humulone (8) and lupulone (22), as possible bactericides. The main mode of action of these compounds activity against bacterial cells is their ability to chelate metal ions and allow passive diffusion of these complexes out of cells. A number of chemical derivatives have been synthesised and, using a model developed as part of this research, tested for their potential to pass metal ions from aqueous to non-polar organic media. In addition to this some of the novel compounds have been screened on bacterial samples to determine the structure activity relationship of the known and novel derivatives. Chapter 1 covers the background ofhumulone (8) and the hop acids. Chapter 2 covers the biology ofthe hop acids including biological activity. Chapter 3 covers the structural analysis of the hop acids. collected during this project and the derivatisation work. Chapter 4 covers the physical property data and biological data collected during this project. Chapter 5 gives a brief summary of the achievements of this project and future directions. Chapter 6 covers the experimental techniques and collected data.

Fusarium oxysporum Schl. var. vanillae (Tucker) Gondon is known to cause root rot in Vanilla planifolia Andrews in most regions where it is grown, including the major plantations in Xishuangbanna, Yunnan Province of China. This is of serious economic concern to the Province since the vanilla flavouring extractable from the beans of the plant is a valuable food product and an important export commodity. There are no fungicides registered for the control of Fusarium root rot and the only available chemical control methods are ineffective and cause serious contamination of the soil. Breeding for resistance is difficult when no dominant gene is known or where little information is available on fungal pathogenicity. Biocontrol is the main alternative for disease control in this crop, an attractive approach because of increasing concerns for environmental protection. The investigation considers two biocontrol strategies: first the introduction of virulent, antagonistic, non-pathogenic strains, closely-related to the pathogen, to overcome pathogenic populations in infected soils; second the use of essential oils with antimicrobial properties when applied to infected soils. Pathogenicity tests have been done on 81 out of 87 F. oxysporum isolates collected in Yunnan Province. Among these, 32 isolates were non-pathogenic and 49 were pathogenic. The pathogenicity results showed the complexity of F. oxysporum in Yunnan. Seventeen isolates were recovered from the Daluo plantation, of which 14 were pathogenic isolates and 3 non-pathogenic isolates; 26 from the Menglun plantation, in which 12 were pathogenic and 14 were non-pathogenic; 18 isolates from the Manjingdai plantation, in which 12 isolates were pathogenic, whilst the other 6 were non-pathogenic and 20 were obtained from the plantation in Hekou i County, of which 11 were pathogenic isolates and 9 were non-pathogenic. Genetic diversity within this population of F. oxysporum has been investigated with respect to vegetative compatibility and to determine the relationship between VCGs and virulence. The VCG results showed that the 87 strains of Fusarium oxysporum f.sp vanillae isolated from Yunnan Province were complex. They could be distributed into 12 different VCGs and that a direct relationship between VCGs group and virulence could not be drawn. Two non-pathogenic strains, ML-5-2 and HK-5b-4-1, have been screened from 87 strains as candidate biocontrol agents by pathogenicity and VCG, which are self-incompatible and closely related to the pathogens. These two strains were effective in vanilla root rot control in controlled environments, but their effects in field experiments were less conclusive. Seven essential oils, which have long been regarded as having inhibitory effects on pathogens in nature, have also been investigated as biocontrol agents. Three oils, cinnamon oil, thyme oil and clove oil, were effective in inhibiting the growth of pathogen in vitro. These oils may develop into useful components of different management strategies with non-pathogenic strains. For the future, consideration will need to be given to the mechanism(s) of the interaction of the antagonistic components with the soil microbe population and host plant and also to appropriate formulation, to take account of soil type, crop status, cultural practices, environmental and economic factors. Biocontrol methods have considerable potential but must be acceptable to farmers as part of an overall crop management programme.