Inulin

Inulin is the reserve carbohydrate material found in the plants of the composite family.

The medicinal plants containing inulin are dandelion, chicory, elecampane, Pyrethrum, and burdock. Plate 77, Figs. 1 and 2 show masses of inulin in dandelion and Pyrethrum.

In these plants the inulin occurs in the form of irregular, structureless, grayish-white masses (Plate 77). In powdered drugs inulin occurs either in the parenchyma cell or as irregular isolated fragments of variable size and form. Inulin is structureless and the inulin from one plant cannot be distinguished microscopically from the inulin of another plant. For this reason inulin has little or no diagnostic value. The presence . or absence of inulin should always be noted, however, in examining powdered drugs, because only a few drugs contain inulin.

When cold water is added to a powder containing inulin it dissolves. Solution will take place more quickly, however, in hot water. Inulin occurs in the living plant in the form of cell sap. If fresh sections of the plant are placed in alcohol or glycerine, the inulin precipitates in the form of crystals.

Plate 77. Inulin (Inula helenium, L.).

1. Inulin in the parenchyma cells of dandelion root.

2. Inulin from Roman Pyrethrum root (Anacydus Pyrethrum, [L.] D. C.)

Mucilage

Mucilage is of common occurrence in medicinal plants. Characteristic mucilage cavities filled with mucilage occur in sassafras stem (Plate 66, Fig. 2), in elm bark (Plate 66, Fig. 1), in althea root, in the outer layer of mustard seed, and in the stem of cactus grandiflorus. In addition, mucilage is found associated with raphides in the crystal cells of sarsaparilla, squill, false unicorn, and polygonatum.

When drugs containing mucilage are added to alcohol, glycerine, and water mixture, the mucilage swells slightly and becomes distinctly striated, but it will not dissolve for a long time. Refer to Plate 79, Fig. 6.

Mucilage, when associated with raphides, swells and rapidly dissolves when added to alcohol, glycerine, and water mixture. The mucilage is, therefore, different from the mucilage found in mucilage cavities, because it is more readily soluble.

In coarse-powdered bark and other mucilage containing drugs the mucilage masses are mostly spherical or oval in outline (Plate 66, Figs. 2 and 3) the form being similar to the cavity in which the mass occurs.

Acacia, tragacanth, and India gum consist of the dried mucilaginous excretions.

Hesperidin

Hesperidin occurs in the epidermal cells of short and long buchu. It is particularly characteristic in the epidermal cells of the dried leaves of short buchu. In these leaves the hesperidin occurs in masses which resemble rosette crystals (Plate 54, Fig. 1).

Hesperidin is insoluble in glycerine, alcohol, and water, but it dissolves in alkali hydroxides, forming a yellowish solution.

Volatile Oils

Volatile oils occur in cinnamon stem bark, sassafras root bark, flowers of cloves, and in the fruits of allspice, anise, fennel, caraway, coriander, and cumin.

In none of these cases is the volatile oil diagnostic, but its presence must always be determined.

When a powdered drug containing a volatile oil is placed in alcohol, glycerine, and water mixture the volatile oil contained in the tissues will accumulate at the broken end of the cells in the form of rounded globules, while the volatile oil adhering to the surface of the fragments will dissolve in the mixture and float in the solution near the under side of the cover glass. Volatile oil is of little importance in histological work.

Tannin

Tannin masses are usually red or reddish brown. Tannin occurs in cork cells, medullary rays of white pine bark (Plate 48, Fig. B), stone cells, and in special tannin sacs.

The stone cells of hemlock and tamarac bark and the medullary rays of white pine and hemlock bark contain tannin.

Tannin associated with prisms occurs in tannin sacs in white pine and tamarac bark. These sacs are frequently several millimeters in length and contain a great number of crystals surrounded by tannin.

Deposits of tannin are colored bluish black with a solution of ferric chloride.

Aleurone Grains

Aleurone grains are small granules of variable structure, size, and form, and they are composed of reserve proteins. They occur in celery, fennel, coriander, and anise, fruits, in sesame, sunflower, curcas, castor oil, croton oil, bitter almond, and other oil seeds.

In many of the seeds the aleurone grains completely fill the cells of the endosperm, embryo, and peristerm. In wheat, rye, barley, oats, and corn the aleurone grains occur only in the outer layer or layers of the endosperm, the remaining layers in these cases being filled with starch.

In powdered drugs the aleurone grains occur in parenchyma cells or free in the field.

Structure Of Aleurone Grains

Aleurone grains are very variable in structure. The simplest grains consist of an undifferentiated mass of proteid substance surrounded by a thin outer membrane. In other grains the proteid substance encloses one or more rounded denser proteid bodies known as globoids. In other grains a crystalloid - crystallike proteid substance - is present in addition to the globoid. In some grains are crystals of calcium oxalate, which may occur as prisms or as rosettes. All the different parts, however, do not occur in any one grain. In castor-oil seed (Plate 77a, Fig. 8) are shown the membrane (A), the ground mass (B), the crystalloid (C), and the globoid (D).