Medicinal plants in therapy

One of the prerequisites for the success of primary health care is the availability and use of suitable drugs. Plants have always been a common source of medicaments, either in the form of traditional preparations or as pure active principles. It is thus reasonable for decision-makers to identify locally available plants or plant extracts that could usefully be added to the national list of drugs, or that could even replace some pharmaceutical preparations that need to be purchased and imported. This update article presents a list of plant-derived drugs, with the names of the plant sources, and their actions or uses in therapy.

The pharmacologic fate of 2,5-diaziridinyl-3,6-bis(carboethoxyamino) 1,4-benzoquinone (AZQ NSC-182986) by intracarotid or intravenous administration in beagles

Beagle dogs received either intravenous (I.V.) or intracarotid (I.C.) 14C ring labelled 2,5-diaziridinyl-3,6-bis-(carboethoxyamino) 1,4-benzoquinone (AZQ) at a dose of 2 mg/kg. Blood, urine and cerebrospinal fluid (CSF) samples were collected at intervals. At varying times, dogs from each group were sacrificed and histologic examination and drug determinations were performed on the major organs. By both routes of administration, the elimination of AZQ from plasma was biphasic with an initial half-life of 18 min and a terminal half-life of 26 hr. The apparent volume of distribution was 7.9 l/kg and the total clearance was 3.5 ml/kg/h. The 96 hr cumulative urinary excretion of total 14C was 41% of the administered dose, including 4% as the unchanged drug. At 1, 48, and 96 hr after I.C. AZQ, drug concentrations in the brain tissue were twice those by the I.V. route. High drug concentrations in the CSF were produced by both routes, although the CSF to plasma ratio was higher by I.C. than I.V. In extracranial organs, tissue concentrations of AZQ were at least twice as high by I.V. than by I.C. administration. No significant clinical or neurologic toxicity were noted when AZQ was given I.C. In the dog I.C. administration of AZQ seems to accelerate drug entry into the brain tissue.

A comparison of the inhibition of growth of methotrexate-resistant and -sensitive leukemia cells in culture by triazines. Evidence for a new mechanism of cell resistance to methotrexate

Forty-five 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-(3-X-phenyl)-s-triazine inhibitors of dihydrofolate reductase (DHFR) and methotrexate (MTX) were tested on L5178Y/R murine tumor cell culture. The concentration of inhibitor causing a 50% decrease in growth rate was determined, and from these results a quantitative structure-activity relationship (QSAR) was developed. This QSAR is compared with QSAR for the same inhibitors acting on isolated DHFR and on L5178Y cell culture sensitive to MTX. The results show that very potent triazine inhibitors of resistant tumor cell growth can easily be made by making the triazines strongly hydrophobic. The optimum pi value for inhibition of MTX-sensitive cell culture is 0.8, while pi 0 for the resistant cell culture is about 6.0. The QSAR for MTX-sensitive and -resistant tumor cell culture inhibition is compared with the corresponding QSAR for Lactobacillus casei cells. Both the mammalian and bacterial cells appear to protect themselves from the highly hydrophilic MTX by erecting lipophilic barriers.

Comparison of quantitative structure-activity relationships of the inhibition of leukemia cells in culture with the inhibition of dihydrofolate reductase from leukemia cells and other cell types

A set of 2,4-diamino-5-(3-X-phenyl)-s-triazines was used to inhibit the growth of tumor cells (L5178 leukemia) in culture. The molar concentration (C) of triazine causing 50% reduction in the rate of cell growth was used to develop a quantitative structure-activity relationship: log 1/C = 1.32 pi - 1.70 log (beta.10 pi + 1) + 0.44I + 8.10, where pi is the hydrophobic constant for X, beta is a disposable parameter, and I is an indicator variable for congeners containing a -CH2Z-C6H4-Y moiety (Z = O or NH). This equation is compared with similar equations derived for the inhibition of dihydrofolate reductase from leukemia cells and bovine liver.