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The emergence of resistant strains of Plasmodium falciparum and Mycobacterium tuberculosis underscores the need for novel drugs that are effective against these microorganisms. As part of our screening programme of the flora of Puerto Rico, we tested a number of ethanol extracts of higher plants for antiplasmodial and antimycobacterial activities. A total of 40 extracts belonging to 23 plant families and 37 species were tested for antiplasmodial activity. Five extracts demonstrated activity against Plasmodium falciparum in vitro (50%-100% parasite suppression at 5 microg/mL). Another 63 extracts belonging to 30 plant families and 50 species were tested in vitro against Mycobacterium tuberculosis. Two extracts were found to be active, Ficus citrifolia and Pisonia borinquena (85% or more inhibition of microbial growth at 100 microg/mL of extract)., (Copyright 2001 John Wiley & Sons, Ltd.)

Three man synthetic routes to analogues of tacrine are described: reaction of anthranilonitriles with cyclohexanone and other ketones, reaction of various anilines with alpha-cyanoketones, and reactions involving anilines and cyclic beta-ketoesters. Although tacrine has a wide range of pharmacological effects, it is best known as an inhibitor of cholinesterase enzymes. Many of the analogues that have been made have not been tested against acetylcholinesterase or butyrylcholinesterase activity. Consequently, there is limited information from which a detailed understanding of structure-activity relationships can be derived. However, some halogenated derivatives are not only more potent acetylcholinesterase inhibitors than tacrine, they are also more selective for acetylcholinesterase than for butyrylcholinesterase.

Several novel analogues of tacrine have been synthesized and tested for their ability to inhibit acetylcholinesterase, butyrylcholinesterase, and neuronal uptake of 5-HT (serotonin) and noradrenaline. Changes in the size of the carbocyclic ring of tacrine produced modest potency against cholinesterase enzymes. Addition of a fourth ring resulted in compounds with marked selectivity for acetylcholinesterase (AChE) over butyrylcholinesterase (BChE): e.g. 6-amino-4,5-benzo-5H-cyclopenta[1,2-b]-quinoline (14a) had an IC50 of 0.35 microM against AChE and 3.1 microM against BChE. Some tetracyclic compounds are 100-400 times more active than tacrine as inhibitors of neuronal uptake of serotonin, in particular 13-amino-6,7-dihydro-5H-benzo-[3,4]cyclohepta[1,2-b]quinoline (18), which had an IC50 of 20 nM. These compounds would be expected to facilitate both cholinergic and monoaminergic transmission. They should be worth investigating in models of memory impairment.

From the bulbs and leaves of Hymenocallis expansa (Amaryllidaceae), three alkaloid constituents were identified: (+)-tazettine, (+)-hippeastrine, and (-)-haemanthidine. These alkaloids demonstrated significant cytotoxicity when tested against a panel of human and murine tumor cell lines.

Catalytic antibodies have created a new dimension in protein chemistry. In these studies it is particularly valuable to investigate systems for which natural enzymic catalysts are unknown. At Strathclyde we have examined several ways of preparing homochiral building blocks for organic synthesis. Antibodies that catalyse the Diels-Alder reaction have been characterized. The target reaction was the addition of acetoxybutadiene to N-substituted maleimides, a reaction that should give a pentafunctional homochiral building block. Catalytic antibodies can give insight into the mechanism of catalysis by proteins. We have investigated an adventitious hydrolytic antibody that cleaves activated esters. We have also shown that an antibody raised to ampicillin for analytical purposes catalyses hydrolysis of the beta-lactam ring.

Pyridone structural requirements for activity against murine P-388 leukemia have been extended to isosteric analogs of 3-hydroxy-4-pyridone, a compound previously found to have activity. An amino group can be substituted for the 3-hydroxyl function with retention of activity. A sulfur, but not an amino function, can replace the lactam oxygen in the 2-position. Relocation of the lactam oxygen from the 2- to the 4-position in the pyridine ring also produces active pyridones, including 2-methyl-3-acetoxy-4-pyridone. This compound, which has a T/C value of 179%, is the most active material discovered thus far in the pyridone studies.