The chemical composition of St. John's wort has been well-studied. Documented pharmacological activities, including antidepressant, antiviral, and antibacterial effects, provide supporting evidence for several of the traditional uses stated for St John's wort. Many pharmacological activities appear to be attributable to hypericin and to the flavonoid constituents ; hypericin is also reported to be responsible for the photosensitive reactions that have been documented for St. John's wort. With regard to the antidepressant effects of St John's wort, hyperforin, rather than hypericin as originally thought, has emerged as one of the major constituents responsible for antidepressant activity. Further research is required to determine which other constituents contribute to the antidepressant effect.Evidence from randomised controlled trials has confirmed the efficacy of St John's wort extracts over placebo in the treatment of mild-to-moderately severe depression. Other randomised controlled studies have provided some evidence that St John's wort extracts are as effective as some standard antidepressants in mild-to-moderate depression. There is still a need for further trials to assess the efficacy of St John's wort extracts, compared with that of standard antidepressants, particularly newer antidepressant agents, such as the selective serotonin reuptake inhibitors (recent comparative studies with fluoxetine and sertraline have been conducted). Also, there is a need for further studies in well-defined groups of patients, in different types of depression, and conducted over longer periods in order to determine longterm safety. St John's wort does appear to have a more favourable short-term safety profile than do standard antidepressants, a factor that is likely to be important in patients continuing to take medication.Concerns have been raised over interactions between St John's wort and certain prescribed medicines (including warfarin, ciclosporin, theophylline, digoxin, HIV protease inhibitors, anticonvulsants, selective serotonin reuptake inhibitors, triptans, oral contraceptives) ; advice is that patients taking these medicines should stop taking St John's wort, generally after seeking professional advice as dose adjustment of conventional treatment may be necessary.

This paper reviews the chemistry, pharmacology and clinical properties of Echinacea species used medicinally. The Echinacea species Echinacea angustifolia, Echinacea pallida and Echinacea purpurea have a long history of medicinal use for a variety of conditions, particularly infections, and today echinacea products are among the best-selling herbal preparations in several developed countries. Modern interest in echinacea is focused on its immunomodulatory effects, particularly in the prevention and treatment of upper respiratory tract infections. The chemistry of Echinacea species is well documented, and several groups of constituents, including alkamides and caffeic acid derivatives, are considered important for activity. There are, however, differences in the constituent profile of the three species. Commercial echinacea samples and marketed echinacea products may contain one or more of the three species, and analysis of samples of raw material and products has shown that some do not meet recognized standards for pharmaceutical quality. Evidence from preclinical studies supports some of the traditional and modern uses for echinacea, particularly the reputed immunostimulant (or immunomodulatory) properties. Several, but not all, clinical trials of echinacea preparations have reported effects superior to those of placebo in the prevention and treatment of upper respiratory tract infections. However, evidence of efficacy is not definitive as studies have included different patient groups and tested various different preparations and dosage regimens of echinacea. On the basis of the available limited safety data, echinacea appears to be well tolerated. However, further investigation and surveillance are required to establish the safety profiles of different echinacea preparations. Safety issues include the possibility of allergic reactions, the use of echinacea by patients with autoimmune diseases and the potential for echinacea preparations to interact with conventional medicines.

A new microplate assay for cytotoxicity testing using A. salina has been developed and shown to give results comparable to a previously published test-tube method. The assay reliably detected all of the compounds toxic to KB cells in a series of 21 pharmacologically active agents, except for two which require metabolic activation in man. Four quassinoids with cytotoxic and antiplasmodial activity were also toxic to the brine shrimp while quassin itself was inactive in all three systems. It is proposed that this assay provides a convenient means by which the presence of cytotoxic quassinoids may be detected during the fractionation of plant extracts.

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New drugs are urgently required for the treatment of amoebiasis, leishmaniasis, malaria and trypanosomiask. In this review the potential of natural plant products as a source of antiprotozoal drugs is discussed with respect to biochemical differences between protozoa and hosts. Some of the ways in which pathogenic protozoa differ biochemically from their human hosts are described, and the modes of action of some antiprotozoal drugs which exploit these differences are mentioned. A selection of natural products of plant origin (alkaloids, terpenes, quinones and miscellaneous compounds) is illustrated with emphasis on their modes of action and potential for the development of selective antiprotozoal agents.

Protozoa are responsible for a number of serious tropical diseases including amoebiasis, leishmaniasis, malaria, and trypanosomiasis. New drugs are required for the treatment of these diseases and the potential of plants to produce new clinical agents is discussed.

Indian Neem tree is known for its pesticidal and medicinal properties for centuries. Structure elucidation of large number of secondary metabolites responsible for its diverse properties has been achieved. However, this data is spread over various books, scientific reports and publications and difficult to access. We have compiled and stored structural details of neem metabolites in NeeMDB, a database which can be easily accessed, queried and downloaded. NeeMDB would be central in dissipating structural information of neem secondary metabolites world over. Background: Neem tree (Azadirachta indica A. Juss), native to Indian sub-continent, has long been recognized for its pesticidal and medicinal properties[1, 2]. It has gained the distinction of being the most researched tree in the World. Extracts of neem fruit, seeds, seed kernels, twigs, stem bark and root bark have been shown to possess repellent, anti-feedant, insect growth regulatory (IGR), anti ovipositional, fecundity and fitness reducing properties on insects [3]. Many species of insects are known to be sensitized by neem formulations [3, 4]. Diverse biological properties of neem are due to many secondary metabolites found in various parts of the tree. Major constituents of its metabolite pool such as Azadirachtin, Azadirone, Gedunin, Meliacarpin, Nimbin, Salannin, Vilasinin groups were proved to be significant pesticidal and/or medicinal principle [5]. Crude extracts of neem are found to be more potent than pure Azadirachtin [6] suggesting there are many more compounds in the neem extract, which even at low concentration have potentiating abilities.

Interaction between the flavones casticin and artemetin and the antimalarial activity of chloroquine and qinghaosu (QHS) was examined using an in vitro growth assay based on [3H]hypoxanthine incorporation in synchronized cultures of a cloned line of Plasmodium falciparum. Casticin, and to a lesser extent artemetin, selectively enhanced the inhibition of growth by QHS, but had little effect on the activity of chloroquine. The findings suggest that flavones indigenous to Artemisia annua, from which QHS is isolated, might significantly alter the clinical potential of this novel antimalarial drug in the treatment of chloroquine-resistant malaria.