Drying in direct sunlight is not recommended. You should spread the material sparsely and dry under shade.

I always avoid direct sunlight. Air drying is more suitable for most phytochemical analysis.

In my lab we air dried them in room temperature with the aid of circulating air flow using fan... direct sunlight may destroy some heat sensitive phytochemicals

Yes I agree with Jovale Vincent Tongco that heat sensitive phytochemicals may denature or destroy under hear. Some are photo sensitive too.

Lyophilize. Freeze drying preserves the phytochemicals quite well. Enzymes are inactive, no microbes can grow, there is no heat, and hydrolytically-unstable compounds remain stable. We freeze dry all leaf, stem, bark, root, and cell culture tissue before analysis. It works great. The dried material can be stored in a freezer for years without significant degradation of phytochemicals. Oily materials, like seeds, do not freeze dry. Also, you are will lose a certain fraction of volatile compounds to evaporation.

As everyone answered, the shade drying is recommended for almost plants, however some of the plants are also dry in sunlight or artificial heat. Its only depends on its phytoconstituents.

Dear Syed Omar,

you may check the link http://www.gardenherbs.org/preserving_herbs.htm

to view complete information and of-course it may depends on nature of the plant,volatile principles present etc.,

cover your parts of plants by paper and put this in dry & dark area for few days. After drying; colour of leaflets remain green, and you observed minimun loss of constituents.

We use standard methods ( for prevent destroy phytochemicals, and especially antioxidants): for beads, leaves, grass, flowers - in tracing paper, no direct sun, at room temperature and in a well-ventilated area (3 days - 1 week). For seeds, fruits, berries, tubers and so forth we use drying oven with natural convection (60 degrees Cels.) - 1-2 nights enough. This way show good results for antioxidants and polyphenol assays.

Lyophilization is the best way to get sample dry but as it is costlier process and can be applied for small quantity of sample or sample that are very precious.

But drying at 40 dgree C in oven is economical and also it doesn't effect the phytoconstituents of sample.

Thanks to all: Really interesting and helpful answers. We almost use the same shedding and air dry proceedure but I got some good ideas as well, eg, low heat ovens, lyophilization, vacuun drying and covering of plants by means of paper etc. Thank you indeed for the nice and good suggestions.

Thank you Dr. Chando for the goog and valuable site on herbs. Our area (Balochistan) is one of the reachest medicinal plants province but unfortunately no resources /experties for exploration and identification of these plants. Very few plants have been explored and worked upon until now. Thank you indeed.

Our area (Balochistan) is one of the reachest medicinal plants containing province but unfortunately no resources /experties are available for exploration and identification of these plants. Very few plants have been explore, identified and worked upon until now.

Indeed, it depends on the phyto-constituent of interest. But the most common technique we use is shade drying!!

Thank you Harita.

Syed, it sounds like you have exciting opportunities for discovery of medicial plants. Botanical identification is a rare skill anywhere, I imagine even more so in your area.

I know of a group that may be able to help you: The Global Institute for BioExploration (GIBEX) at http://www.gibex.org. They are a non-profit group dedicated to teaching scientists, students, and non-scientists with innovative, very low-cost, and portable drug-discovery tools and technologies that can be used directly in the field. GIBEX members merely educate and consult, they respect local intellectual property rights and do not seek anything in exchange.

As a start, you can train students or non-technical people to deploy GIBEX tools to collect data in remote regions. The costs for materials are very low and you can build the kits yourself. You can evaluate some potential biological activities of plants and use local common names if botanical expertise is unavailable. With preliminary pharmacological data, you may find it easier to locate experts to take the next steps. It is definitely worth contacting GIBEX.

Respected Justin Maresh, Thank you very much for your valuable information. Yes indeed I will definately contact GIBEX. I had no idea of it before. Thank you indeed.

Chukwunonye Ojinnaka, University of Port Harcourt.

In tropics where freeze drier may not be very available, medicinal plants (roots, leaves and seeds) are air dried, spread the material on a filter paper and leave on a bench with the windows open allowing limited light. Turn the material constantly for three or more days. The organic components will not be photo- oxidized.

Respected Chukwunonye Ojinnaka, We do use the same proceedure as you mentioned above. It was interesting in our case that the part having some light was ok instead some part of having no light was degraded. May be due to moisture or any other reason. Any how thank you indeed for your reply.

This is my opinion based on experience.The best way to drying of medicinal plants is in the room under sunlight exposure (not directly under sunlight) with good air ventilation. But to stored the medicinal plants for certain period without change the chemical ingredient, it should be firstly process via grinding and extraction. The extracted medicinal plants solution could be dry wether via freeze-dried method or drying in the incubator under 35c temperature. The extract powder should be packed in the air-proof container before store in the cool room or freezer untill use.

Thank you Ahmad for your interesting and important procedure. Indeed it will help us in future. Regards

Step 1: Plant material should be shade dried before its extraction without direct sunlight exposure

Step 2: Course grinding of the plant material

Step 3: Desired method of extraction i.e. cold or hot maceration

Step 4: Filtration of the extract

Step 5: Concentrate the extract as desired in a rotary evaporator under vacuum

Step 6: Store the final concentrated extract in air tight container under dark conditions in a refrigerator

Thank you Tariq bhai. Regards

My suggestion is to use freeze dryer, otherwise shade drying could be an alternative way.

You are right Mahdi, thank you indeed.

Freeze-drying I think its the best option to dry your samples and preventing oxidation of important compounds like phenolics.

Thank you Dr.D. Pandya and V. Spinola for your interesting answers and suggestions.

Regards

Dear Syed,

We use following conditions at our institute.

After collection and the taxonomic identification, the plant sample is shade dried for x days (depend upon plant sample) followed by drying in an oven preset at 45 degree C for x days (depends on plant sample). The sample is then powdered in a mixer grinder, sieved through 85 mesh (BSS) and stored in an air tight container.

Thank you Bhavesh for the method. Yes this is a good way as well.

Hi Syed Umer,

For the pharmacological evaluation, shade drying in laboratory conditions would be preferable and easier. Exposure to direct sun light may induce phytochemical reactions since the cells will be alive. 

Thank you indeed Ali A. Razzaq and Aditya Rao.

Many natural product chemists have put forward different ways of drying plant materials based on locality and avalaibility of equipment but the best method is still AIR DRYING THE PLANT MATERIAL IN AN AIRY LABORATORY (PREFERABLY, NEAR A WINDOW) WITH LIMITED SUNLIGHT.

Yes exactly well established method. Thank you indeed Chukwunonye M S.

I supported to Justin J Maresh answer, for ideal method for the drying the plant sample. It works well and can be use further up to 1 year without any significant changes. 

you can see this article Article Effect of Drying Temperature and Air Velocity on the Essenti...

freeze drying is the best method .

as my knowledge, suitable and easy method is dry using dehydrator with fan under 40 to 45 C, 24 to 48 hours.

Very true

• I think one of the methods/instruments that can be useful and has less been considered for this category of sensitive products is the use of a dehumidifier (even home type) that can be used to dry the product at low temperatures, in complete darkness and at the same time to recycle essential oils/volatile substances.

Very right

According to standard procedure, plant materials have to dried under shade for 2 weeks

Plant phytochemicals basically cannot be destroyed by direct sunlight drying. The plants needs and used the the same sunlight energy for phytochemicals metabolism, so its ironical to say sunlight destroy phytochemicals,and as such sunlight heat can not destroy plant phytochemicals. In a nut shell phytochemicals cannot be destroyed by any amount of temperature, but at very high temperatures Above 300 degrees Celsius it can only be transformed to another active compound. So I suggest you dry your plants before pulverisation with direct sunlight taking it back to its source from where it was harvested( sunlight) for reasonable yield or else experience microbial degradation and poor extract yield