Physical and chemical properties of sporopollenin exine particles

Barrier, Sylvain

Abstract

The chemical structure of sporopollenin was extensively reviewed, along with some considerations pertaining to its physical and biological properties. A comparative study is presented of extraction protocols to isolate exines from L. clavatum, in particular, but with extension to spores from other species, namely, Lycopodium spec., Ambrosia trifida, Aspergillus niger and Chlorella vulgaris. Physical aspects of the materials extracted were studied, including size (highlighting large and small types of commercial “Lycopodium”), wall thickness, mechanical resistance and density.

Encapsulation of a wide variety of compounds in sporopollenin microcapsules was investigated using passive, vacuum, compression and centrifugation methods. Diverse products, with molecular weights ranging from less than 1kDa to 464kDa, were successfully encapsulated in exines, including both polar (e.g. dyes, proteins, carbohydrates and oligonucleotides) and non-polar products (e.g. oils and waxes). It was shown that a protein, alkaline phosphatase, does not lose its initial activity after it has been encapsulated in exines and subsequently released.

Sporopollenin was found to grant oils protection against photooxidation triggered by UV light and the extinction coefficient of sporopollenin was determined (20,000-40,000m¯¹). Protective abilities offered by exines to oils against aerial oxidation, and refining effects of sporopollenin on rancid fats, were studied, completed by a preliminary investigation of sporopollenin’s redox characteristics. A flavour test on 20 volunteers showed that exines mask the taste of encapsulated cod liver oil up to a 1/1 (w/w) loading level.

Sporopollenin was also used in solid-phase organic synthesis. It was established that the reaction of ammonia, primary aliphatic amines and aniline with sporopollenin formed an amide bond on a carboxylic group of the sporopollenin. A short diamine was attached to sporopollenin in order to construct a spacer arm by further reaction between the free amino end and succinic anhydride. Sporopollenin was derivatised with bromine and chlorine by addition to the unsaturated functional groups, substitution of the hydroxyl groups and chloromethylation of the aromatic rings. The attached halogen atoms were then successfully substituted by azide and thiols. The thiol availability to nucleophilic substitution and formation of disulphide bridges was assessed.

Citation

Barrier, S. Physical and chemical properties of sporopollenin exine particles. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4213615

• Thesis Type: Thesis
• Deposit Date: Jan 14, 2013
• Publicly Available Date: Feb 22, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4213615
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Jul 1, 2008