Adopting a method for extraction of secondary plant metabolites will depend on the type of plant material and the nature of the compound to be extracted. Initial fractionation by using solvents of different polarity to obtain a fraction rich in the interested group followed by separation & isolation of individual compounds by using different chromatographic and partition techniques will be very much helpful.

Very Lengthy answer!!!

This is the answer that I got from a Yahoo Answers:

Are you talking about the precursors to polymers like all the celluloses and lignins, or about the polymers themselves? Are you talking about small molecule hormones like auxins, gibberellins, and other plant regulators? Isoprenoids and terpenoids? Xanthophylls?

A great deal depends on the CLASS or TYPE of target molecule.

It also depends on the stage of development and tissue you plant to extract: seedling leaf, root, or stem? seed/embryo? the flower of a flowering plant? cultured single plant cells? Extraction often needs to consider the type of cell wall: does it have just a primary cell wall (cellulose) or secondary cell wall too (lignified)?

Classic extraction: tissue of most, if not all types, are cut into small pieces (roots and stems not more than 3-5 mm cubed, leafs into 5 x 5 mm squares) and placed in a ceramic mortar. Pour in liquid nitrogen and let free. While in the liq N2, start pulverizing into fine powder with pestle

Other extraction: cut into pieces and homogenize in aqueous buffer (use phosphate or tris buffers at pH 7.0-8.0). You might require additives, such as metal chelators, reducing agents (thiols) or other anti-oxidants (make sure additives do NOT react with your class of compounds and only put in additives if they provide a protective function against loss or conversion of your target metabolites!)

Centrifuge well (maybe 20,000 g for 15-30 min). If your metabolites are lipophilic, consider liq-liq organic separation of the supernantant in a separatory funnel. Solvents to consider using are methanol, diethyl ether (explosive! use peroxide-free), dichloromethane and/or chloroform, hexane, and petroleum ether.

Your centrifuge pellet may also contain the target metabolites, especially if potentially insoluble in aqueous extraction buffer or it partititions to lipophilic membranes that pellet out. Consider using a 50-100% methanol, ether, or hexane extraction of the pellet too.

Work up your sample for analysis (by SPE, GC-MS, HPLC, TLC, capillary electrophoresis) as usual.

Also Attaching some important link and pdf's.

http://link.springer.com/protocol/10.1007%2F978-1-61779-624-1_13

I fully support Mr. Arvind Negi. No doubt he contribute well in giving answer of a very typical question.

Regards

SALMAN AHMED

Ph.D Fellow

Hello there,

As for my knowledge, rotary evaporator is used to recover the solvent after solvent extraction finally getting crude extract free from solvent. If you are doing hot soxhlet extraction, then you can recover your solvent just by simple distillation method. But care should be taken that secondary metabolites you are concentrating will not get denatured during distillation. Hope this helps... 

Adopting a method for extraction of secondary plant metabolites will depend on the type of plant material and the nature of the compound to be extracted. Initial fractionation by using solvents of different polarity to obtain a fraction rich in the interested group followed by separation & isolation of individual compounds by using different chromatographic and partition techniques will be very much helpful.

i do agree with subrata de it depends upon the plant material and the secondary metabolite you are wishing to extract even methanol  can extract a wide variety of compounds keeping for maceration 1:10  ratio. methanol has boiling point of 64.7 °C so if you don't have rotary evaporator simply dry it in hot plate with 40°C it will evaporate very fastly

Since the solvent used for extraction, methanol, is hygroscopic in nature, it easily absorbs moisture from the air. So the extract could not be left open as for other solvents (which evaporate when left open). It is advisable that you go for simple distillation and condensation (not exceeding 40 °C ). Hot plate might sometimes result in charring thereby degrading the bioactive principles.

yes charging may take place so care should be taken but at min temp there is   less chances for  formation of artifacts 

You can use a water bath to evaporate the methanol.

2.2 实验方法

2.2.1 代谢物萃取

1)        取100mg葡萄样品于2ml 离心管里，加入60μl 核糖醇（0.2mg/ml in dH2O）。Sample grape (100mg) in 2ml tubes. Add 60 ml of  Ribitol (0.2 mg ml_-1 stock in dH2O) as an internal standard;

2)        加入0.5 ml甲醇氯仿混合液（体积比3:1），70Hz 5min研磨仪处理，70℃烘箱10min；

Add 0.5ml of the extraction liquid (Vmethanol: Vchloroform=3:1). To homogenize the tissue, place steels balls into the sample tubes and insert samples into the tubes. Homogenize in ball mill for 5 min at 70 Hz. Treat for 10 min at 70 ℃;

3)        紧接着将样本4℃，12000rpm离心15min；

Centrifuge for 15 min at 12000rpm,4℃;

4)        小心地取出0.4ml上清于2ml进样瓶（甲烷硅基化的）中；

Transfer 0.4 ml from the supernatant into a fresh 2ml GC/MS glass vial.

2.2.2代谢物衍生化

1)        在真空浓缩器中干燥提取物；

Dry in a vacuum concentrator without heating;

2)        向干燥后的代谢物加入80μl甲氧胺盐试剂（甲氧胺盐酸盐，溶于吡啶20mg/ml），轻轻混匀后，放入烘箱中37℃孵育2h；

Add 80μl of methoxyamination reagent (20mg/ml. in pyridine), Shake for 2 h at 37 ℃;

3)        向每个样品中迅速加入100μl BSTFA（含有1% TCMS，v/v）,将混合物70℃孵育1h；

Add 0.1 ml of the BSTFA regent (1% TMCS,v/v) to the sample aliquots. Shake for 1 h at 70 ℃;

4)        冷却至室温，上机检测。

GC-MS analysis when the temperatu res get down to the room temperature

These books may be useful:

Plant Secondary Metabolites

Makkar, Harinder P.S., Sidhuraju, P., Becker, Klaus

2007, XII, 130 p. 18 illus. A product of Humana Press. ISBN 978-1-58829-993-2

----------

Protocols for In Vitro Cultures and Secondary Metabolite Analysis of Aromatic and Medicinal Plants

Jain, Shri Mohan, Saxena, Praveen K. (Eds.) 2009. A product of Humana Press.ISBN 978-1-60327-286-5

---------

Plant Secondary Metabolites (Methods in Molecular Biology)

Hardcover – August 28, 2007

by Harinder P.S. Makkar (Author), P. Sidhuraju (Author). ISBN-13: 978-1588299932

--------

and maybe:

Official Methods of Analysis of AOAC INTERNATIONAL

Kindly Refer to the papers/book chapters of T.W.Goodwin and Loomis. They are old but very helpful.

As far as I know there is no a standard protocol for plant extraction yet. Hence,  choosing a method  depends on your preference and justifications.