Agree with both comments above, the best bet is to dry on shade at room temperature. This way the metabolites get concentrated from the moist loss.

On the other hand extraction with high temperature may destroy many metabolites, especially those of medicinal interest. If you are using polar solvents; i.e. ethanol, extraction at room temperature may yield better results as you can "rinse" the vegetal samples up to four times. If you really need to use water you may use other extraction methods like soxhlet, to avoid the loss of some volatile compounds. But again, be advised hydrolysis is favored at higher temperatures.

UNDERSTAND THE PLANTS AND ITS PHYTOCHEMISTRY are keyed in the use of herbal medicine. Sometimes plant matters are boiled fresh, some times it is boiled dried at high or low temperature---these different methods are done for reasons. If we look for heat extraction materials and do not want any other lighter molecules or compounds, we want to use high heat so that these unwanted materials would be "denatured" or evaporated and leave us with what we seek from high heat. What is left should be what we want. In a simple case of using strong tea against running stomach, we want high heat and boil the tea down to a concentrate. In this case, we are not interested in flavanoids or aroma; we just need tanin to obtain anti-emitic effect. However, if we use the tea for other purpose, we might extracted differently, i.e. different temperature, dried, or fresh, etc. 

If we look for something that is not water soluable, we may extract through the use of alcohol. Somethings we use both to be efficient in the extraction. Working with the same plant, we may use alcohol extraction first and then remove the plant matter into a secondary extraction by boiling water.

DRYING depends on the availability of resources. In ethnomedicine where drying equipment may not be available, sun dry is a common practice. If properly laid, sun dry could be very effective. Generally, the length of time of sun exposure in order to fully dry the materials does not lead to significant denaturing of the compounds we seek from the plant. Sun dried tea leaves still makes the dried leave smell and taste "tea."

I agree with above comment.. As for my experience, using drying cabinet (even-though we used low temperature) were not suitable for rhizome with essential oil as main  compound, or compound that we intent to isolate

thank you for all guidance...., my topic is using dried young leaves part and planned for water boiling method, in order to mimick regular oral administration of drug by human...