The bio-chemistry of alkaloids / by T.A. Henry.

  • Henry, Thomas Anderson, 1873-1958.
Date:
[1927]
Catalogue details

Licence: Public Domain Mark

Credit: The bio-chemistry of alkaloids / by T.A. Henry. Source: Wellcome Collection.

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    difficult than that of alkaloids in the other group. We may however take some encouragement from the fact that it is not many years since it was found that Bil- harziosis, which is such a plague in Egypt, can be effectively treated by this drug. With the characteristic exasperation of therapeutic research, another specific for this disease, namely tartar-emetic, was discovered almost at the same time. IV. GENERAL DISCUSSION. Chairman: One of the questions raised by Dr Henry was the reason for these alka¬ loids in plants, and he mentioned the suggestion, though I do not think he proved it, that they might be protective. Plants run great risk from insects, and I think it can be said with certainty that the presence of alkaloids is no protection. I remember how greatly the seed and seed capsules of a poppy in Ceylon were attacked by a butterfly which ate them, and in this country the Hemlock has a moth that eats inside it. There is not much evidence that alkaloids are a protection. One question I would like to ask is whether you (Dr Henry) think there is any prospect of replacing the plant as a maker of alkaloid. In my business, as an Economic Entomologist, we are very dependent on nicotine as an insecticide, but getting it from the tobacco plant is expensive, and if we could have nicotine replaced com¬ mercially, we think perhaps it would make a difference. Dr Pethybridge: I should like to know if it holds good in most cases that manuring has no effect on the quantity of alkaloid developed. I remember trying to grow tobacco in Ireland, which could be smoked, and in our first efforts the proportion of nicotine was about something like 14 per cent., and the smoking of it was perfectly vile. We were told that the reason was that it had had too much nitrogenous manure, and certainly the fact was proved. i Mr Howes : I should like to ask Dr Trevan why it is that any native races who make use of arrow poisons can eat the fish without fear of consequences; they use poisoned arrows for game and eat the flesh. Surely these things have alkaloids in them. Is it merely distributed all over the animal and dispersed in small quantities? Chairman : One of the things which attracts one about all the alkaloids is how extra¬ ordinarily specific they are in their action. In the use of alkaloids as insecticides, it is found that one will be extraordinarily toxic, and a closely related one will have no action whatever. I assume that nicotine is present as nicotine in growing leaves of the tobacco plant, but in spite of that there are a large number of caterpillars which will live and flourish on these leaves, whereas if one gets the nicotine out and puts it on the outside, the caterpillar will eat it and die. It may be that the nicotine is not present in the plant but is produced by fermentation? Dr Henry : With regard to the synthesis of alkaloids, it is very unsatisfactory for a chemist to have to confess that although we have been at work on these things for a long time, there is not, at the present time, any case in which a natural alkaloid has been replaced commercially by its synthetic equivalent. The nearest approach is cocaine, which has been developed by Robinson’s process, and sparteine has been put on the market, which is not a very good substitute. In the special case of nicotine, I do not think very much attention has been given to that, but it is a more promising