Alkaloid-free lupins

Alkaloid concentrations in the plant are in the same order or even higher than the inhibitory concentrations against pathogens that have been established experimentally. Alkaloid-free lupins are highly susceptible to herbivore predation, which shows that the alkaloids are obviously important for the survival of a lupin plant. 

Fig. 1.3 Importance of quinolizidine alkaloids for lupins against herbivores.ln this experiment, lupins with or without alkaloids were grown in the field. When rabbits got into the field, they preferentially consumed the sweet, alkaloid-free lupins. Also larvae of mining flies preferred sweet lupins.

Owing to the use of lupin seeds for feeding animals, much attention has been given to the selection of species free from the more toxic alkaloids of the group, particularly sparteine, to methods of removing alkaloids from the seeds, a subjeet on which there is an extensive literature and to methods of estimating alkaloids in lupins on which a critical review has been published by Brahm and Andresen. ... 

Lupinua alkaloids. In lupines the alkaloids seem to be generated in the sprouts (271, 272), and a downward movement seems to be responsible for the appearance in the roots. Experiments with grafts indicate that low alkaloid yielding strains of lupines are able to metabolize these alkaloids to other substances (271), and Mothes and Engelbrecht (273) confirmed this by grafting lupines on other Leguminosae which do not elaborate alkaloids. They showed that the isolated roots in aseptic cultures synthesized no alkaloid when entirely free of hypocotyls. Wagenbreth (245) draws attention to errors that can result from unobserved adventitious roots, and others (183, 274) stress sources of error which may arise from inadequate analyses. 

The second important mineral nutrient, potassium, seems to be much easier to control, and the results are clear for alkaloids that are derived from amino acids. Smith (1965) found that the degrading enzyme A-carbamyl putrescine to putrescine is greater in leaves of potassium-deficient barley. Depletion of potassium usually results in an increase in the percentage of alkaloids in plants, while the total amount per plant is sometimes decreased. Results for tropane alkaloids were published by James (1950), Dafert and Siegmund (1932), and El-Hamidi et al. (1965). In lupines the results were similar to those obtained for tropane alkaloids, i.e., the potassium-depleted plants had a higher alkaloid level (Mironenko, 1965, 1975 Andreeva, 1952). Alkaloid-free plants, e.g., some species of Trifolium,... 

The function of quinolizidines as defense compounds can be observed in the example of sweet lupins, an alkaloid-free breeding form. In contrast to the alkaloid-containing wild form. 

Has been used for food and feed in both the eastern and western hemispheres. Its seed contain 30-40% protein and 17-23% fat, so, like soybeans, lupine is a high-protein seed as well as a potential oil source (Salunkhe et al, 1992). The fatty acid composition of Lupinus mutabilis is reported to be 1% myristate, 13% palmitate, 1% palmitoleate, 5% stearate, 42% oleate, 34% linoleate and 3% linolenate. The protein is rich in lysine and has good nutritional properties. Lupines contain bitter, toxic alkaloids that limit their appeal. Lupine seeds can be debittered by washing with water. There are sweet lupine varieties that are free of alkaloids, but these varieties contain much less oil. 

Figure 3.4a. The effect of exposure of plants to light on the composition of lupine alkaloids. Top Artificial light plants were grown in July, the plants exposed 18 hr were additionally illuminated with 4000 lux during the twilight hours, and the plants exposed 12 and 9 hr were covered to shorten the time of exposure. Bottom Natural light plants were planted at month intervals hence, their growth rate was according to their location, Poznan, Poland. The curves represent the concentration of free and esterified alkaloids in the total plant in mg/100 g of plant material (dry weight). The numbers represent the milligram contribution of free alkaloids (ALK) and hydroxylupanine ester fraction (HEF). Formulas lupanine (I) a free alkaloid, and cinnamoyloxylupanine (II) a HEF (Nowacki et ai, 1973). Courtesy of the journal.

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