Art. LIII.—Preliminary Notes on the Isolation of the Bitter Substance of the Nut of the Karaka Tree (Corynocarpus lævigata).
[Read before the Wellington Philosophical Society, 1st July, 1871.]
A very interesting as well as a most important investigation in any country, whether for toxological or for scientific purposes generally, is that which has for its object the identification and examination of the particular principle to
which is due those poisonous or other marked effects which may have been observed on the administration of certain of its plants or herbs, or parts of them, to the animal system.
But especially is this the case in the country we are now setting, the character of its Flora being in certain respects peculiar, and in many cases greatly divergent from that of any other country we are yet acquainted with, any addition, therefore, from such a quarter to the number of active principles recognised can hardly fail to be of value, as enabling us to attain to a more comprehensive view of the whole subject of vegetable medicinals or poisons—the manner of their association with other principles or with particular orders or parts of plants—and lastly, the mode in which they operate in producing their individual effects; while there is besides the chance that any principle so isolated and identified may be more useful medicinally, and more readily administered when separated from the plant.
Altogether the subject appears to be one eminently worthy of careful attention, and I have therefore from time to time examined many of those plants which have come the more prominently under notice by reason of their acknowledged potency in respect of the characters stated.
The last subject of these investigations has been the kernel of the fruit of the Karaka tree, which, as is pretty well known, is extremely poisonous to man if taken in an unprepared state; and though I have not yet completed it, sufficient knowledge has I think been arrived at to render a statement of the results so far obtained interesting.
Not having personal acquaintance with the mode in which the karaka berry is prepared as food by the natives, nor of its action as a poison, I am indebted to Mr. W. Colenso, F.L.S., for the following accurate information:—
“1. Preparation as food.—The kernels were prepared for food thus:—In the autumn a large party would go to the karaka woods on the sea-coast, which were mostly rigidly preserved (tabooed), to gather the fruit; this was generally done by beating them down with a long pole (hence the term, “ka haere ki te ta karaka”—the verb ta, to hit, or strike, sharp, short, sudden blows with a stick; the same verb is used in speaking of the operation of tattooing), after which they gathered them up into baskets. In, or near, the adjoining beach large pits were dug for earth ovens, into which, when ready, the karakas were poured, and the earth banked up in the usual way. These ovens were left several hours before they were opened, generally till the next day, or even longer, when the karakas were taken out, put in baskets, laced up, and placed under water, often at the mouth of some neighbouring stream or quasi lagoon, where also they remained some time (I believe a day or two at least), for the double purpose of destroying all remains of the poisonous quality, and for the loosening and getting rid of the skin and flesh (sarcocarp) of the fruit. When
they were washed clean by knocking them about pretty roughly to rid them of the outer skin, etc., taken out, spread in the sun on mats and stages, and carefully dried; and when quite dry again put up in new baskets for winter use, for feasts, for distinguished visitors, and for gifts to friendly chiefs and tribes residing inland.
“As the same karaka woods did not bear alike plentifully every year, the years of barrenness were to the tribe seasons of calamity and want, the karaka being one of their staple vegetable articles of food.
“2. The symptoms attending cases of poisoning through eating the raw kernel were—violent spasms and convulsions of the whole body, in which paroxysms the arms and legs were stretched violently and rigidly out, accompanied by great flushings of heat, protrusion of the eyes and tongue, and gnashing of the jaws, but unattended by vomiting (very different in appearance and result from the bite of the poisonous spider, katipo, of which I have also seen and attended several cases, which are of a much more mild type, and never fatal). I mention this as both were likely to be caused in the same locality (near the uninhabited sea-shore) and season, and at first by a tyro might be mistaken. Unless speedily attended to the poisoning by karaka quickly proved fatal; and even in those few cases in which I have known natives to recover very likely it was more owing to the small quantity of the poison received into the system, than to the means used as internal remedies. As the sufferers were invariably little children, they were more easily dealt with; and to prevent the limbs becoming distorted, or stretched and rigid, a pit was quickly dug, into which the child was placed in a standing posture, with its arms and legs bound in their natural position, and the mouth gagged with a bit of wood to prevent the sufferer biting its own tongue; and there the child was left, buried up to its chin, until the crisis had passed by; sometimes it was also plunged repeatedly into the sea before being pitted. Fortunately the cases of karaka poisoning were but few, owing, no doubt, to the hard texture and disagreeable taste of the karaka kernel in its raw state; very much fewer than those arising from the eating of the sweet fruit of the tutu (Coriaria, which latter, however, were more easily managed by the natives.
“The writer well recollects having seen at Wangarei (Bream Bay), in the years 1836–9, a fine healthy youth of about 12 years of age, who had been recovered from poisoning by karaka kernels. He, however, had not been properly attended to, as to the tying of his limbs in their right position while under the influence of the poison, and he was therefore now a curious spectacle, reminding one of the instrument called a caltrops more than anything else. One leg was curved up behind to his loins, and the other bent up in front with the foot outwards; one arm inclined behind his shoulder, and the other
slightly bent and extended forwards; and all, as to muscles, inflexibly rigid. He could do nothing, not even turn himself as he lay, nor drive off the sandflies (which were there in legions) from feasting on his naked body, nor scratch himself when, itching, nor put any food to his mouth. He was the only child of his parents, who, fortunately for him, were both alive and took great care of him, turning and shifting his position very often by day and night, as, from his body not evenly resting, he could not possibly remain long in one position. When not asleep he was laughing (if not eating), and greatly enjoyed his being so placed that he could see the children at play, in which he always encouraged them by his voice, often seeming the merriest of the village. I frequently sat by his side during my visits, to talk with him, and to drive away the tormenting sandflies, which he would beg me to do. His skin was remarkably fine and ruddy—I might call it pretty—being wholly without eruption, blemish, or scar; his teeth pearly white, and voice and laugh regularly strong, hearty, and ringing. His eyes were very brilliant and of an intelligent cast; but in conversing with him I always thought his intellect was not so sharp (or developed) as ordinarily that of Maori boys of his age.”
This interesting account discloses the fearful nature of the poison of the karaka nut, and also that the Maoris employ two distinct processes—baking and washing—in their mode of preparation of this article for food; but it cannot be gathered therefrom whether both processes are necessary for the removal of the poison from the kernel, and if not which is the essential one.
It will be noticed that the kernel only is spoken of as being poisonous, the fruit which surrounds it in its natural and ripened state being, as is well known, wholesome and pleasant, though not powerfully flavoured.
In pursuance of my object, therefore, I gathered a quantity of the kernels from which the fruit had completely rotted off, and after removing the woody husk I bruised them very finely and put part to bake at a temperature of 212° for four hours, when it appeared their bitter flavour was destroyed.
The other part I steeped in successive quantities of cold water for two days. The steep-water separated from the bruised nut contained a great variety of substances, those positively identified therein being approximately in the order of their relative abundance, -as follows:—vegetable albumen (emulsin), casein (legumin), grape sugar, gum, a bitter substance, and a tasteless essential oil, which latter floated in greater part on its surface. The solid insoluble part of the nut left after the successive additions and abstractions of water was nearly tasteless, and completely devoid of all bitterness, and showed a resemblance in chemical composition to the insoluble part of hazel nuts.
The competence of either of the processes used by the Maoris (baking or washing) in the preparation of the nut, for the decomposition or removal
of the bitter part of it, being thus shown, it naturally occurred to me that this bitter might be the poisonous part of the nut. I therefore made the isolation of this principle for the present my first object.
The bitter part in question was soon found to be capable of absorption, by animal charcoal, and of removal therefrom by hot alcohol. I therefore took advantage of this deportment to obtain it in a pure state for examination. The details of this process are as follows:—
The kernels are well crushed and triturated with successive quantities of water (cold) till their bitter taste is gone. The solutions thus obtained are rendered distinctly acid to the taste by acetic acid, by which the casein and emulsin present are precipitated, and the filtrate therefrom agitated with animal charcoal till the bitter substance is removed. The charcoal is then collected and mixed with boiling alcohol, and the pure alcoholic solution of the bitter substance thus obtained is allowed to remain for two or three days at common temperatures, when the bitter part crystallizes out in beautifully radiating acicular forms.
The characters of these crystals are as follows:—Intensely bitter; colour white; lustre pearly; feebly acid; at 212° Fahr. melts; gives a dark rose colouration with warm sulphuric acid; soluble in hot water, and feebly so in cold water; soluble in alcohol, also in hydrochloric and acetic acids; soluble in ammonia and potash; insoluble in ether and chloroform; does not give any precipitate with tannic acid, nor with potasso-iodide of mercury, nor potasso-sulpho-cyanide of zinc; does not contain nitrogen.
The evidence as submitted above shows that the principle is not of an alkaloidal nature.
Its deportment with sulphate of copper and potash is strikingly similar to that of digitaline to the same tests. Both give green precipitates of a tint very similar to arsenite of copper. This property of either of these vegetable principles to give green precipitates with copper under these circumstances seems characteristic of them, as, among the numerous substances the most likely of any I know to give this reaction, not one has, on experiment, been ascertained to deport itself in this manner. Thus either of these principles is readily distinguishable in this way from picrotoxia, resins generally (including common resin), soaps, gums, and the bitter principle of Phormmium tenax.
The green precipitates formed in this way by the bitter of the karaka and digitaline respectively are, however, readily distinguished from each other by subjecting them to a rise of temperature (120° Fahr. to 212° Fahr.); that containing the digitaline is unaffected, while the other precipitate speedily changes its colour to yellow, the copper being reduced to the sub-oxide, as if grape sugar were present. Further, if the proportion of the karaka bitter to the copper and potash is not properly adjusted, reduction commences at once.
It appears, however, that if the solution of digitaline is boiled with acid prior to the mixing with copper and potash, a great reduction of the copper will take place on raising their temperature to 200° Fahr.
Taking all these facts into consideration, I am inclined to believe that the bitter of the karaka nut is a glucoside, and that digitaline falls into the same class, though I have not known-this character imputed to it before.
An appropriate name for this bitter principle of the karaka will be, I think, karakine, and this name, therefore, I propose to give it.
Having failed, after a careful examination of the nut for vegetable alkaloids, to find any principle having the characters of these bodies, I conclude that the bitter substance bere treated of (karakine) is the poisonous part of it; but not having sufficient of this principle separated to allow of a proper trial of its effects upon the animal system, I am unable to confirm or disprove the correctness, of these surmises, but I hope at an early date to be able to supplement this paper by a statement of results of experiments undertaken to settle the question.
As being connected with this subject I may state, in conclusion, that the inner bark of the tree is also bitter, probably from the presence of karakine. The outer bark is not bitter, but astringent from the presence of tannin, while the sap, the wood, and the leaf (which is, I hear, wholesome to cattle) taste sweet (sugar), with not the least bitterness. These observation were taken in July.