Phenolic extracts of almond peel containing procyanidins, propelargonidins, and prodelphinidins, and method for preparation thereof
The present disclosure concerns phenolic extracts containing procyanidins, propelargonidins and prodelfinidins obtained from peel of the almond [ Prunus dulcís (Mili.) D. A. Webb, Prunus amygdalus (L.) Batsch., Amygdalus dulcís (Mili.), Amygdalus communis (L.) or Prunus communis (L.)]. In particular, the objective is to obtain extracts rich in proanthocyanidins with type-A bonds. The preparation method disclosed comprises: (a) a maceration of plant material with organic solvents at 25-100° C., (b) purification by liquid-liquid extraction and/or adsorption or ion exchange chromatography, and (c) optionally, a final drying. Also disclosed are the possible activities/properties of these extracts such as anti-oxidant activity and others, which determine the use thereof as a nutritional or health ingredient, and the use thereof in the cosmetic and pharmaceutical industry.
1. An extract of almond skin, wherein said extract of almond skin has a phenolic content greater than about 50 mg/g, and wherein said extract of almond skin comprises dimers and trimers of A-type proanthocyanidinins in a percentage of at least about 1.77% by weight of the total phenolic content, wherein the dimers and trimers of A-type proanthocyanidinins include procyanidins, propelargonidins and prodelphinidins.
2. The extract of almond skin of claim 1 , wherein the percentage of dimers and trimers of A-type proanthocyanidinins is between about 1.77% and 4.61% by weight of the total phenolic content.
3. The extract of almond skin according to claim 1 , obtained by a process comprising:
a) obtaining the almond skin from an almond fruit, said obtaining comprising at least one of blanching, peeling, toasting, grinding, and combinations thereof;
b) extracting the obtained skin with an organic solvent-selected from methanol or ethanol, pure or mixed with water, further comprising an organic or inorganic acid, wherein said extracting step is carried out by at least one of the following:
(i) ultrasound bath,
(ii) overheating the organic solvent at a temperature between about 60° C. and about 180° C. and at a pressure between about 500 psi and about 3000 psi, or
(iii) reflux; and
c) purifying the extract, said purifying comprising at least one of extracting with a solvent, adsorption, and ion exchange chromatography.
4. The extract of almond skin of claim 3 , wherein the process further comprises drying the purified extract.
5. The extract of almond skin of claim 3 , wherein said obtaining step further comprises defatting the skin with an organic solvent.
6. The extract of almond skin of claim 5 , wherein the organic solvent is hexane.
7. The extract of almond skin of claim 3 , wherein the purification step is carried out by extraction with at least one of ethyl acetate, acetone, n-butanol, iso-propanol, and mixtures thereof.
8. The extract of almond skin of claim 3 , wherein the purification step is carried out by adsorption or ion exchange chromatography on a resin by elution in alcohol gradient of 20% and 80%.
9. A pharmaceutical composition comprising the extract of almond skin of claim 1 and a carrier.
10. The extract of almond skin of claim 3 , wherein the acid is selected from the group consisting of HCl, H 2 SO 4 , H 3 PO 4 , acetic acid, citric acid, or a cationic resin in protonated form.
11. The extract of almond skin of claim 4 , wherein the drying is carried out at a temperature below about 40° C.
12. The extract of almond skin of claim 4 , wherein the drying comprises at least one of lyophilisation, concentration, vacuum drying, air drying, and spraying.
13. The extract of almond skin of claim 3 , wherein the extraction step (b) is carried out in an ultrasound bath at a temperature between about 25° C. and about 100° C., for a time between about 2 hours and about 24 hours.
14. The extract of almond skin of claim 13 , wherein the organic solvent of extraction step (b) is methanol/HCl in a proportion of 1000:1 by volume; wherein the extract is purified by extraction with ethyl acetate; and wherein the purified extract is concentrated to dry at a drying temperature below about 40° C.
15. The extract of almond skin of claim 3 , wherein the organic solvent of extraction step (b) is ethanol/HCl at pH=3; wherein the extract is purified by column chromatography; and wherein the purified extract is vacuum dried at a drying temperature below about 60° C.
16. The extract of almond skin of claim 3 , wherein the extraction time is about 4 hours.
17. The extract of almond skin of claim 3 , wherein the extraction step (b) is carried out with the organic solvent overheated between about 100° C. and about 140° C., and wherein the extraction time is between about 1 minute and about 6 hours.
18. A functional food or dietary supplement comprising the extract of almond skin according to claim 1 .
19. The extract of claim 1 wherein the procyanidins comprise catechin units.
20. The extract of claim 1 wherein the propelargonidins comprise afzelechin units.
21. The extract of claim 1 wherein the prodelphinidins comprise gallocatechin units.
22. The extract of claim 1 wherein the procyanidins comprise epicatechin units.
23. The extract of claim 1 wherein the propelargonidins comprise epiafzelechin units.
24. The extract of claim 1 wherein the prodelphinidins comprise epigallocatechin units.