Natural Stains

Man has used natural Stains for many years for various purposes and few natural dyes are still in use today also. But after availability of artificial or synthetic dyes natural dyes have lost their charm and shine.

Main important natural stains are as follows which are still widely used in the field of bacteriology.

Indigo:

This dye is of basically plant originated and mostly it is obtained from genus indigofera. Te species of this plants contains glucoside named inidican which on fermentation yields the stain indigo

Indigo carmine :

This stain is available in form of sodium salt of indigo disulphonic acid and it is having typical indigo blue color and acidic staining property due to presence of disulphonic acid

Cochineal:

This dye is insect origin and it is obtained by grinding the dried bodies of the female insect coccus cacti and extracting with water. Cochineal has limited affinity for tissues so has limited applicability when used alone. It becomes powerful stain when converted into carmine.

Carmine :

This stain is derivative of cochineal. When cochineal is treated with alum or any other metal stilts it is converted to carmine. Carmine is a valuable nuclear stain and widely used in practicals meiosis and mitosis . exact chemical formula of carmine is not cleared.

Litmus :

Litmus is also obtained from the same lichens as orcien by treating the plants first with lime and soda , followed by ammonia, and air. Litmus is believed to be a mixture of colored compounds but the primary principle is known as azolitmin. Its exact formula is also not cleared

Orcein :

The precursor of orcein is obtained from the lichens lecanora tinctoria and roccella tinctoria so it is lichens based stains. Originally it is colorless crystalline m phenolic compounds, one of these is orcinol which changes to orcein, a violet-colored compound, on the addition of ammonia and oxygen. It is a weakly acidic stain. The formula of orcien is not known.

Brazilin:

This principle is obtained by extracting the bark from brazilwood. It is colorless when freshly extracted but becomes oxidized to the red stain brazilein on exposure to air.