Medicinal and Aromatic Plants
FOXGLOVE ( Digitals lanata Enrh ). An exotic biennial herb, cultivated mainly in central and southern Europe for leaves which contain glycosides used for heart stimulation. India imports a major parts of its requirements of this drugs. The crop perfers silty-loam to clayey-loam soils, rich in organic matter and temperate climate ( 1200-2000 m above the sea-level ). The seed-rate used is 500 grammes per hectare. The nursery is raised in early spring and seedlings, when 8-10 weeks old, are transplanted, 30×45 cm to 60×60 cm apart, depending upon the soil fertility . It is an irrigated crop and makes only a moderate , mainly as nitrogenous and phosphatic fertilzers. The plants flower in the second year, but the flowering stalks are removed to induce a larger leafy growth . In general, one harvest of the leaf crop is obtained in October in the first year, whereas 3 harvests of leaf crop are obtained in the second year. The average yield recorded in India in the second year is 600 kg/hs ; higher yield up to 1,500 kg are reported from elsewhere. Digitalis leaves are thermolabile and hygroscopic and therefore, should be rapidly dried at 40 C immediately after collection. They should contain 0.1% glycoside ( digoxin , digitoxin, gitoxin , etc. ) calculated as lanatocide-c and not more than 5% moisture. The leaves could be stored in the form of coarse powder in airtight containers placed in a cool and a dry place.
DILL OR SOWA( Anethum graveolens Linn. ). Sowa is a rabi crop grown alomost throughout the country for its fresh aromatic leaves used in cooking, and its fruits are marketed as a common condiment. The fruits contain an essential oil, rich in carvone and is used in pharmacy for the preperation of dill water and similar preperations to treat flatulence, abdominal and colic pain. India exports dill fruits worth about Rs 2 million annually. There are two known varieties, viz. the East Indian Dill ( A. graveolens var. sowa ) and European Dill ( A. graveolens Linn.) ; the former alone is cultivated in India commercially; its oil possesses superior aroma, but is considered inferior in pharmacy owing to the presence of a toxic substance (dillapiole) which is, however, easily removed.
The aromatic plants possess odoriferous and volatile substances which occur as essential oils, gum exudate, balsam and oleo-resin in one or more parts, viz. root, wood, bark, foliage, flower and fruit. The chemical nature of these aromatic substances may be due to a variety of complex the chemical compounds. Many of these aromatics are powerful germicides and have anti-bacterial properties, but the bulk of the produce finds use in perfunery and the food-flavouring industries. Amongst the two, the per-fumeru and allied industries consume much larger amounts of the natural fragrant material. According to the UN Word Statistics (1972), the annual world trade (excluding countries in eastern Europe ) in essential oils and perfummery aromatics for 1969 was of the order of Rs 2250 million; also, a large quantity of the aromatic material of plant orgin is utilized in cosmetics, toiletries and allied industries. Our current volume of foreign trade in the perfumery material, essential oils and aromatic compounds is around Rs 65 million and this amount accounts for 1.6 per cent of the world trade. Some sixty-two types of essential oils come to the international market with a large and consistent demand. However, our treatement of the aromatic plants is confined to a few more important essential-oil crops grown in the country.
The methods employed to obtain aromatic substances from plants are classifed into distillation, enfleurage, maceration, expression and solvent extraction. Expect in the case of flowers crops, such as jasmine and kewara in which the fragrant constituents are likely to be decomposed or destroyed, the essential oils are mostly obtained by distilling the produce; in fact, steam distillation is the oldest method of separation of essential oils. The perfumery material is filled in a large-galvanizediron still over a perforated netal grid. Water is filled in the still below the level of the grid so that it generates a low-pressure steam on heating to pass through the material. The water vapours carry with it the essential oil of the perfumery material. These vapours are passed through a condenser and collected in a vessel where the oil is ecanted with a seperating-funnel.