Structural characterisation of rubber from lactarius mushrooms; 1H-NMR analysis of terminal groups in the rubber chain

Ohya Norimasa, . and Tanaka Yasuyuki, . Structural characterisation of rubber from lactarius mushrooms; 1H-NMR analysis of terminal groups in the rubber chain. pp. 84-94. ISSN 1511-1768

The initiating species and termination step of rubber biosynthesis have been identified by structural characterisation of both terminal groups with H-NMR for rubber from sporophores of Lactarius volemus. The sequence of trans- and cis-isoprene units along the chain was determined using polyprenol-18 and ficaprenol-11 containing two-trans and three-trans sequences respectively as models. The initial dimethylallyl-trans-trans- sequence was observed in the rubber from L. volemus. This demonstrates that the initiating species of rubber formation in L. volemus is trans trans-farnesyl diphosphate. The presence of hydroxyl and fatty-acid ester terminal groups in the rubber indicates that the termination reaction can be hydrolysis of polyprenyl diphosphate. The fraction corresponding to the highest molecular weight of L.volemus rubber had the trans-trans-(cis) -sequence but contained only trace amounts of the dimethylallyl group. The occurrence of a selective modification of the dimethylallyl group after polymerisation was presumed for the highest molecular weight rubber. The mechanism of rubber formation in Hevea brasiliensis is discussed on the basis of the structural information obtained from Lactarius mushroom rubber.

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Abstract

The initiating species and termination step of rubber biosynthesis have been identified by structural characterisation of both terminal groups with H-NMR for rubber from sporophores of Lactarius volemus. The sequence of trans- and cis-isoprene units along the chain was determined using polyprenol-18 and ficaprenol-11 containing two-trans and three-trans sequences respectively as models. The initial dimethylallyl-trans-trans- sequence was observed in the rubber from L. volemus. This demonstrates that the initiating species of rubber formation in L. volemus is trans trans-farnesyl diphosphate. The presence of hydroxyl and fatty-acid ester terminal groups in the rubber indicates that the termination reaction can be hydrolysis of polyprenyl diphosphate. The fraction corresponding to the highest molecular weight of L.volemus rubber had the trans-trans-(cis) -sequence but contained only trace amounts of the dimethylallyl group. The occurrence of a selective modification of the dimethylallyl group after polymerisation was presumed for the highest molecular weight rubber. The mechanism of rubber formation in Hevea brasiliensis is discussed on the basis of the structural information obtained from Lactarius mushroom rubber.

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Item Type:	Article
AGROVOC Term:	Rubber
AGROVOC Term:	Hevea brasiliensis
AGROVOC Term:	Lactarius
AGROVOC Term:	Biosynthesis
AGROVOC Term:	Biochemistry
AGROVOC Term:	Sporophores
AGROVOC Term:	Extracts
AGROVOC Term:	Fractionation
AGROVOC Term:	Ginkgo biloba
AGROVOC Term:	Ethanol
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 06:28
URI:	http://webagris.upm.edu.my/id/eprint/23315

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