Phytochemistry (v.56, #3)

GRAPHICAL ABSTRACTS (vii-viii).

Appreciation and communications in honour of the retirement of Jeffrey Harborne FRS as Editor of Phytochemistry by G.Paul Bolwell; Norman G. Lewis; Dieter Strack; Phytochemistry Regional Editors (217-218).

Ecological biochemistry and its development by E.Arthur Bell (223-227).
The concept that chemistry and biochemistry may play significant roles in ecological relationships is not a new one. It is only within the last quarter of a century, however, that this concept has gained general acceptance and ecological biochemistry has become a well defined interdisciplinary subject in its own right. Examples are given of different types of biochemical relationships involving plants and animals and reference to other areas of the subject are made.
Keywords: Danaus plexippus; Asclepias species; Cardenolides; Pyrrolizidine alkaloids; Flavonol glycosides; 3-Hydroxy-2-butanone; Caryedes brasiliensis; Dioclea megacarpa; Canavanine; Eumaeus atala florida; Zamia floridana; Cycasin; Feeding deterrents; Polymorphism in plants; Cyanogenic glycosides; Polymorphism in herbivores; Adaptation to monofluoracetate;

Jeffrey Harborne and his co-workers have played a unique role in the over-all study of plant pigments and of anthocyanins in particular through their many publications and through Jeffrey's editorial work with Phytochemistry. Jeffrey has made important contributions to our understanding of the separation and structural identification of anthocyanins; to co-pigmentation; and to the role of anthocyanins in systematics and ecology in both reproductive and vegetative tissues. This work has had considerable influence on much of the current research on the genetics and regulation of anthocyanin biosynthesis.
Keywords: J.B. Harborne; Anthocyanins; Phytochemistry;

Phytochemistry and medicinal plants by J.David Phillipson (237-243).
A truncated history of the contribution of plants to medicine is given with reference to some of the less well known ancestors of the Harborne family. Six of the top 20 prescriptions dispensed in 1996 were natural products and the clinical use of drugs such as artemisinin, etoposide and taxol has once more focussed attention on plants as sources of novel drug entities. High through-put robotic screens have been developed by industry and it is possible to carry out 50,000 tests per day in the search for compounds which have specificity of action against a key enzyme or a subset of receptors. Bioassay-guided fractionation of plant extracts linked to chromatographic separation techniques leads to the isolation of biologically active molecules whose chemical structures can readily be determined by modern spectroscopic methods. The role of academics in the search for new drugs is discussed by reference to some of our research into natural products with activity on the central nervous system, on pain receptors, the malaria parasite Plasmodium falciparum, the wound healing properties of the sap of species of Croton (Dragon's blood), and a traditional Chinese medicine used to treat eczema. Expertise in phytochemistry has been essential for this research and the strong lead shown by Professor Jeffrey Harborne is gratefully acknowledged.
Keywords: J.B. Harborne; Medicinal plants; Phytochemistry; Academics; New drugs; Central nervous system; Eczema; Malaria; Pain; Wound healing;

Jeffrey Harborne and colleagues have been responsible for collating the majority of data on the role of flavonoids in insect–plant interactions. This article examines some of this information and assesses our knowledge about the role flavonoids play in insect feeding and oviposition behaviour. It is clear that insects can discriminate among flavonoids and that these compounds can modulate the feeding and oviposition behaviour of insects, but further work is required to understand the neural mechanisms associated with these behavioural responses. Despite the wealth of data about the diversity of flavonoids in plants, very few of these compounds have been tested against insects and their role in the evolution of host range in insect–plant interactions has yet to be determined.

A brief review is given of some biological, chemical and chemotaxonomic aspects of phytoalexin research. Emphasis is placed on the search for antifungal compounds in the plant families Leguminosae and Rosaceae, and in rice, Oryza sativa. The possible role of phytoalexins in the resistance of rice plants against the fungus Pyricularia oryzae (=Magnaporthe grisea) is discussed, and the future prospects of phytoalexin research are outlined.
Keywords: Leguminosae; Rosaceae; Gramineae; Rice; Oryza sativa; Plant–fungal interactions; Phytoalexins; Preformed antifungal compounds;

Polyhydroxylated alkaloids — natural occurrence and therapeutic applications by Alison A. Watson; George W.J. Fleet; Naoki Asano; Russell J. Molyneux; Robert J. Nash (265-295).
Over one hundred polyhydroxylated alkaloids have been isolated from plants and micro-organisms. These alkaloids can be potent and highly selective glycosidase inhibitors and are arousing great interest as tools to study cellular recognition and as potential therapeutic agents. However, only three of the natural products so far have been widely studied for therapeutic potential due largely to the limited commercial availability of the other compounds.
Keywords: Glycosidase; Inhibitors; Pyrrolidines; Piperidines; Pyrrolizidines; Indolizidines; Nortropanes; N-Containing sugars;

Bryophytes contain a large number of terpenoids and phenolic compounds. Recent topics relating to the chemical constituents found in 36 Japanese, 3 New Zealand, 2 European, 1 Argentinean and 1 Taiwanese liverworts and 2 Japanese mosses and their biological activity are discussed. The chemosystematics of some liverworts as well as the chemical relationship between liverworts and mosses, and bryophytes and ferns are also discussed.
Keywords: Bryophytes; Liverworts; Mosses; Terpenoids; Bibenzyls; Bis(bibenzyl)s; Biological activity; Chemosystematics;