In dry part no further enzymatic or metabolic alteration  of natural plant product would become possible further. All compounds can be recovered in a natural un altered form, while green leaves due to presence of  chloroplast and active metabolic and protein synthesizing machinery there remains a possibility of formation of new compounds or intermediates or secondary metabolites in respsones to light and other factors.

Thanks Dr. Ravi Kant Upadhyay. Can you please answer the question in the same chain that is there not any possibility of loss of some compound during whole drying process?

There are the reason up their for Ravi Kant Upadhyay gave you.

During extraction process, we always use many chemical solvent. According to those method relate to the plant itself. Dry weight from plant alway give less error from plant while they are still fresh. Because fresh plant materials can changed according to the climate, weather, plant itself when it have grown and transportation before plant were extracted in the laboratory.

Thus, the moisture content in plant can varies from many reason.

For future or reference extraction, dry materials can refer as the portion of how much dry materials (g): solvent or solution (ml) that were used in the protocal. That mean we can repeat many time with less error.

As we are always interested in secondary metabolites of the plants component.  Which is mostly is an exudation of plants and might be present in cell sap. Drying process help us to remove excess water and enzyme action present in the cell. Which restricted plant metabolites mobility and any further degradation. This may also useful in extraction of secondary metabolite from plant material. As loss of unnecessary pigments during drying, loss of extra water during drying, and total mass become higher due to increase in total surface area are some key feature for efficient extraction process.

• As we are concerned with the secondary metabolite prepared in the diferent parts of the plant. if the plant is in dried form then it can be easily extracted with different organic solvents like MeOH, EA, BuOH, DCM, Hexane etc. But if is fresh it contain water in thier parts which alter with different solvent providing opponency for extraction of metabolite in small amounts. the another reason is that fresh plant have chances that compounds present can be converted due to functioning of green parts of the plants.

An increase in a certain compound per fresh weight (e.g. in fruits or vegetables) could be solely accounted for a decrease in fresh weight caused by water loss; thus there could be a difficulty in comparing obtained results with those of other groups, which its turn may cause difficulty in developing standardised protocols.

As per literature review i have found that fresh plant tissue should be used as in fresh tissue there are very less metabolic changes occurrs.

True, the dried parts do not undergo further biochemical reactions. Also there is less chances of contamination with dried parts prior to extraction such as bacteria or fungi. So far better working with dried parts.

Check this related thread for some more opinions on the subject

https://www.researchgate.net/post/Which_do_you_recommend_fresh_or_semi-dry_or_dry_biomass_tissue_for_an_aqueous_solvent_extract_or_for_extracting_isolating_separating_phytochemicals

Dried plant material is free from unuseful matters.Theophin Okay described in his answer.When plant part dried there is no loss of properties and chemicals present in material got in saturated condition. This gives us better result.

• I think I have come little too late to this topic. Whatsoever, let me put another perspective to this topic.
• Sarangadhara ( An eminent Ayurvedic physician, 1400 AD ) had emphasized on fresh drugs ( just collected/ wet ) to prepare the prescribed formulations. In this context, he was also aware of the fact that it is not always possible to get the drugs in fresh condition. So he had also mentioned the dried drugs ( within 1 year of collection ) to use in the formulations.
• The point to be noted here is that when he mentioned about the fresh drugs ( wet/ just collected), he prescribed the amount of the fresh drugs  should be double in quantity to the specified amount mentioned in the formulations. In contrast to this, he prescribed the amount of dry drugs ( within 1 year of collection) should be equal in quantity to the specified amount mentioned in the formulations.
• Whatsoever, he had also mentioned about the exceptional cases. These exceptions are categorized in two groups.
• In first category, he had enlisted the number of substances which should be always taken when they are old ( more than 1 year after the collection). Because he believed this would be beneficial for the curing of disease. The list goes like this ..... E. ribes, P. longum, Jaggery, Coriandrum sativum, Ghee/ Clarified butter & honey.
• In contrast to this, he has mentioned about drugs like T. cordifolia, H. antidysenterica,  A. vasica, B. hispida, A. racemosus, W. somnifera, B. cristata & P. foetida. He prescribed these drugs should always be taken as fresh & should not to be doubled in quantity to the specified amount mentioned in the formulations.

In my own opinion, dried powdered materials will create more space for the solvent to penetrate the cells and collect the secondary metabolites.

Also, rate of biochemical reactions with the dried materials are very poor.

Thanks 

Better to do the experiment, and the target would be the response factor. As for the simple example: one must fermenting the tea or coffee from the fresh before further process; one must keep fresh flower to get different scent of its essential oil; one must do the drying or freeze it before the fishes decay.

When the result of your study shows no different between fresh and dried one, the handling of the production scale would become the major consideration.

So... the target is the answer for answering dried or fresh material.

For the production point of view, handling the fresh material need more energy and attention. Easier to handle the dried one.

First of all we have to dry the product and remove moisture in order to facilitate entry of the organic solvent. Because moisture restricts the entry of organic solvent...in addition; Reducing error in weighting (to calculate extraction efficiency) and also preventing secondary metabolite to occur, could be the reasons.

several consideration:

1. Solvent: if you like to use non-polar; fresh raw material would be not suitable as it's water content. If the solvent is water miscible one, you may calculate its water content

2. Taste matter: if the final extract should represent "freshness" savory or its lie, fresh material would give better taste (not always, some material better on the dried state)

3. Metabolite: there is a biochemical reaction during drying.

4. Cost: the final cost on the production would mostly based on Solvent vs Raw material ratio. More solvent means more energy to evaporate.

The presence of water will effect the extraction while dried plants will will allow the solvent to work without any interactions .