New extraction method for Mitragyna speciosa L.

The investigation carried out with several samples showed unmistakable the

great advantage of the extraction in water. Worth to know that the extract in pure

ethanol cannot be carried out at industrial level for the flammability of the

solvent and the risk of fire or explosion.

1. CAPEX. Although the extraction unit for the extraction in subcritical

water is could cost 50% more of a conventional extractor for hydroalchoholic

solutions we have to consider additional costs for the latter. An

extraction plant that uses ethanol has to be designed ATEX due to the risk

of solvent flammability and explosion. Moreover, the downstream for

ethanol distillation is another relevant cost that makes the choice of

extraction in subcritical water more convenient.

2. Permission, cost, and bureaucracy of ethanol. The use of ethanol

requires an official permission related a well-defined amount declared.

This implies the excise duty, and a regular control of the authorities on the

amount in storage. In Italy the cost of ethanol to extract 250 kg of plant

material is 3,000 euro. This means that the OPEX of ethanol-water

extraction is much higher, water only need a simple plant of filtration and

pretreatment. Employees working with ethanol need to follow courses for

safety.

3. Extraction yields. The overall yield in weight of the extract in subcritical

water is 8-17% higher compared to ethanol or ethanol-water extraction.

4. Extract aspect. The extract in subcritical water is a brownish solid

powder easy to handle. The extract in ethanol or ethanol-water is a

viscous sticky paste very dark because it contains chrophyll and other

pigments.

5. Alkaloids extraction yields. The extract in subcritical water and the

extract in ethanol-water are comparable in term of overall yield. However,

the extraction in water is more selective. If necessary, a preliminary plant

wash with a little volume of water could eliminate salts and sugars.

Selective alkaloids extraction is already observed at 80° and 100°C, then

completed at 150°C.

6. Extracts concentration. The extract in subcritical water can be easily

concentrated by ultrafiltration on polymeric membranes that concentrates

the solution without heating, while the extract in ethanol-water cannot be

treated with membranes (damaged by ethanol).

7. Innovative extraction unit design. The innovative engineering design for

the subcritical water extractor, enables a competitive process with

economic and environmental benefits. Each semicontinuous extraction

step last only 15-25 minutes.