This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
Kava rhizome is the rhizome of Piper methysticum Forster (N.O. Piperacece), a shrub indigenous to the Sandwich Islands. The plant produces a large rhizome which should be freed from roots and periderm, cut into pieces and dried.
Although the British Pharmacopoeia requires that the periderm should be removed, much of the commercial drug is unpeeled. The larger rhizomes are cut into irregularly cubical or wedge-shaped pieces or slices about 1 to 5 cm. thick; the smaller may be entire and have numerous stout roots attached, the drug then exhibits a dark grey periderm within which is a whitish or pale brownish grey cortex and a narrow ring of whitish wood enclosing a large, dense, often discoid pith of the same colour. In the wood slender vascular bundles with distinct vessels alternate with wide medullary rays. This structure is best seen in the smaller rhizomes.
The parenchymatous medullary rays readily break down and the vascular bundles then separate into strands giving to the drug a coarsely fibrous appearance. All the parenchymatous cells are loaded with starch in simple or compound (two to three) grains. The odour is slight and agreeable; the taste at first bitterish but subsequently distinctly numbing.
Kava rhizome contains about 5.8 per cent. of resin, part of which (a-kava resin) is soluble in petroleum spirit, the remainder (β-kava resin) being soluble in ether. In addition it contains methysticin (colourless crystals melting at about 137°; 0.3 per cent.), yangonin (colourless crystals melting at 151°; 0.18 per cent.), and pseudomethysticin (yellowish crystals melting at 113°; 0.18 per cent.); these readily crystallise from a concentrated alcoholic tincture of the drug. Further constituents are an alkaloid, kavaine, two glucosides and an abundance of starch. The medicinal activity appears to be due to the resins.
Kava rhizome is employed medicinally as an antiseptic and diuretic in gonorrhoea and cystitis. The purified resin dissolved in sandalwood oil forms a proprietary preparation for gonorrhoea. It is used in the South Sea Islands for preparing an intoxicating drink, the intoxication being said to affect the power of movement while leaving the intellect clear.