Re: Re: Mildred's question on Retinoic Acid...Rooibos

[Guest guest]

An even better tea is Rooibos, with lots of antioxidants.

Subject: Recent Rooibos Research

Date: Sun, 29 Apr 2001 10:33:45 -0500

J Agric Food Chem 2001 Jan;49(1):114-7

Influence of processing stages on antimutagenic and antioxidant

potentials of rooibos tea.

Standley L, Winterton P, Marnewick JL, Gelderblom WC, Joubert E, Britz

TJ.

Department of Food Science, University of Stellenbosch, Private Bag X1,

Matieland 7602, South Africa.

The antimutagenic and antioxidant potentials of rooibos (Aspalathus

linearis) tea samples, collected from each of its major processing

stages, were evaluated according to the Salmonella typhimurium

mutagenicity test and the hydrogen donating ability and superoxide anion

radical scavenging assays, respectively. Ten random samples were

collected before and after fermentation, as well as after sun-drying,

sieving, and steam pasteurization. Results indicated that the fermented

tea had a significantly (P < 0.05) lower antimutagenic and antioxidant

potential than the unfermented tea. Of the different processing stages,

the most significant reduction in the antimutagenic and antioxidant

property of the tea was found during the " fermentation " step.

Sun-drying, sieving, and steam pasteurization also reduced the

antimutagenic potential of the tea, although not to the same extent as

the first processing step. The hydrogen donating ability was

significantly increased after steam pasteurization in comparison to

those of fermented and sun-dried tea. Pasteurization did not affect

superoxide anion radical scavenging in comparison to fermented tea.

Differences seem to exist in the antimutagenicity and antioxidant

potencies of the tea sampled at the various stages during processing. A

possible role of tea polyphenols in the antimutagenic and antioxdant

activities of the tea is suggested as processing caused a significant

reduction in the total polyphenolic content.

PMID: 11170567 [PubMed - in process]

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Mutat Res 2000 Nov 20;471(1-2):157-66

An investigation on the antimutagenic properties of South African herbal

teas.

Marnewick JL, Gelderblom WC, Joubert E.

Programme on Mycotoxins and Experimental Carcinogenesis, Medical

Research Council, P.O. Box 19070, Tygerberg 7505, South Africa.

@

The antimutagenic properties of South African herbal teas were

investigated using the Salmonella typhimurium mutagenicity assay.

Aqueous extracts of fermented and unfermented rooibos tea (Aspalathus

linearis) and honeybush tea (Cyclopia intermedia) both possess

antimutagenic activity against 2-acetylaminofluorene (2-AAF) and

aflatoxin B(1) (AFB(1))-induced mutagenesis using tester strains TA98

and TA100 in the presence of metabolic activation. A far less inhibitory

effect was noticed against the direct acting mutagens, methyl

methanesulfonate (MMS), cumolhydroperoxide (CHP), and hydrogen peroxide

(H(2)O(2)) using TA102, a strain designed to detect oxidative mutagens

and carcinogens. Depending on the mutagen used, the unfermented tea

exhibited the highest protective effect. A similar response regarding

the protection against mutagenesis was obtained when utilising different

variations of the double layer Salmonella assay. The double layer

technique proved to be more effective to detect the protective effect of

the different tea preparations against the direct acting mutagens. With

respect to indirect mutagens, the highest protection was noticed when

the carcinogen was metabolically activated in the presence of the tea

extract as compared with when the tea extract was incubated in a

separate layer with the bacteria. The current data suggest that two

mechanisms seem to be involved in the antimutagenicity of the tea

extracts towards carcinogens that require metabolic activation: (i) the

tea components may interfere with cytochrome P450-mediated metabolism of

these mutagens and (ii) the direct interaction between the tea

constituents, presumably the polyphenolic compounds, with the

promutagens and/or the active mutagenic metabolites. However, the mild

and/or lack of protection and in some cases even enhancement of

mutagenesis induced by direct acting or oxidative mutagens, provide new

perspectives regarding the role of the polyphenolic compounds known to

exhibit antioxidant properties, in the protection against mutagenesis in

the Salmonella assay. The present study provides the first evidence on

the antimutagenic activity of honeybush tea and further evidence on the

antimutagenicity of rooibos tea.

PMID: 11080671 [PubMed - indexed for MEDLINE]

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