We dried leaves and powder them for increasing surface area, which is resposbile for effecient extraction

Most of the secondary metabolites are useless for the plants and they are not movable from plants and deposited in various place. Drying does not affect the content of these constituent .

Drying leaves correctly is a kind of stabilization of the biological material; so you can store it for a longer time. Dry material can in addition be more easily pulverized for extraction. You can well extract the comminuted material with lipophilic organic solvents; when using water mixable solvents (e.g. alcohols) you can exactly adjust the water content. Solvents can more effectively reach the inner space of the cells because cell walls became permeable during drying.

Careful drying should be performed at ambient temperature under low moisture conditions. However, not all compounds are stable during the normal drying process; if drying is not made cautious enough (e.g. heat drying, stronger violation of the material etc), compartmentation is destroyed and enzymes can become active (e.g. ß-glycosidases which hydrolyse glycosides) or oxidation occurs. Thus for sound research people use liquid nitrogen to frozen the material, then pulverize the material in liquid nitrogen and dry it in a freeze dryer - thawing has to be avoided during the whole process.

To determine the original content of secondary constituents you can of course use fresh material; then take care that extraction is made as soon as possible; determine the water content of the material for exact adjusting the water content of the solvent. Extract with cold solvent using a grinder (e.g. Ultra Turrax).

we can use fresh leaves but we have to avoid chlorophyll pigment

also the plant compounds  will be more stable after ezymes hydrolysis which may happened

to reduce the yield which reduce the time for processing

Three Reasons:

1. To improve Pulverization as the dry leaves will be easy crush or mill

2. Removal of moisture may improve stability due to inhibition of enzymatic reaction

3. To resist growth of microorganisms due to removal of moiture