Exobasidium vexans infection of Camellia sinensis increased 2,3-cis isomerisation and gallate esterification of proanthocyanidins
2004
Punyasiri, P.A.N. | Tanner, G.J. | Abeysinghe, I.S.B. | Kumar, V. | Campbell, P.M. | Pradeepa, N.H.L.
Infection of leaves of tea (Camellia sinensis (Kuntze) L, cv TRI 2025) which was susceptible to blister blight (Exobasidium vexans Massee), resulted in a shift of the proanthocyanidin stereochemistry away from 2,3-trans (e.g. catechin and gallocatechin) and towards 2,3-cis (e.g. epicatechin and epigallocatechin). Infection also resulted in increased gallic acid esterification of the initiating subunits of proanthocyanidins. This was shown by both mass spectroscopy and phloroglucinolysis. Proanthocyanidins isolated from healthy tissue had a predominantly 2,3-trans stereochemistry which accounted for 53% and 61% of the total initiating and extension units of proanthocyanidin, respectively. Conversely in infected tissue, proanthocyanidin subunits with a 2,3-trans stereochemistry accounted for 26% and 40% of the total initiating and extension units, respectively. Infection had little impact on the hydroxylation state of the B-rings of proanthocyanidins. The products of acid hydrolysis under oxidative conditions had a slight excess of di-hydroxylated B-rings with cyanidin accounting for 58.3 +/- 0.05% and 60.4 +/- 0.2% of the total anthocyanidin recovered following hydrolysis of proanthocyanidin isolated from infected and healthy leaves, respectively. Similar results were obtained by phloroglucinolysis.
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