Thea sinensis, presence

CS103 Chaboud, A., J. Rayaud, L. Debourcieu and J. Reynaud. The presence of apigenin-2 -0-glucosyl-6-C-glucosylapigenin or 2 -)-glucosylisovi-texin in the leaves of Thea sinensis Sims. var. macrophylla. Pharmazie 1986 41(10) 745-746. 

Microanalytical techniques, consisting of methaneboronation of the vicinal hydroxyls ( bismethaneboronate or methaneboronate-TMS-ether ) have been developed by Takatsutoet al. for the GC/MS or GC/SIM of brassinosteroids (16). Consequently brassinone (15), 24-ethylbrassinone (12) and 28-norbrassinolide (14) were detected by GC/MS without isolation from Chinese cabbage ( Brassica campestris ), green tea ( Thea sinensis ) and chestnut insect galls ( Distilium racemosum ) (17-19). The presence of brassinolide and castasterone in the tissues of these plants has been also detected. 

Camellia (Thea) sinensis (tea) and Cqffea arabica (coffee) plants. Caffeine was formed rapidly by extracts of green coffee berries, but little by more mature ones, and not at all by seedlings. Biosynthesis of caffein proceeds from 7-methylxanthosine in the presence of an active purine nucleoside phosphorylase or 7-methyl-A -nucleoside hydrolase. Methionine and 5-adenosylmethionine serve as precursors for the methyl groups of purine alkaloids. These act in the presence of methyltransferases on 7-methylxanthine (38) and theobromine (31) to produce caffeine. A pathway for the origin of these compounds in coffee and tea plants has been proposed (Suzuki et al., 1992 Waller and Dermer, 1981) (Fig. 37.10). 

Fluorocitrate. Fluoroacetate is toxic because it is converted in vivo to the (2R, 3R) stereoisomer of 2-fluorocitrate which is a potent inhibitor of citrate transport across the mitochondrial membrane (7) and is also an inhibitor of the citric acid cycle enzyme, aconitase (8,9). Accumulation of 2-fluorocitrate induces convulsions and ultimately heart failure and death. It is interesting that certain plants such as alfalfa Medicago sativa ssp sativa) (10) soya bean Glycine max) (11) and tea Thea sinensis) (12) can accumulate low levels of 2-fluorocitrate when grown in the presence of fluoride suggesting that a wide range of plants possess the ability to biosynthesise fluoroacetate and convert it to 2-fluorocitrate in small quantities. 

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