Anti-oxidative Effects of Rooibos Tea Extract on Autoxidation and Thermal Oxidation of Lipids.

J Oleo Sci. 2009; 58(6): 275-83Fukasawa R, Kanda A, Hara SPowdered rooibos tea extract (RTE), which is rich in polyphenols, is made from rooibos tea by freeze-drying. "Rooibos" is Afrikaans for "red bush," and the scientific name is "Aspalathus linearis." It is a broom-like member of the legume family of plants and is used to make an herbal tea which has been popular in South Africa for generations and is now consumed in many countries. In the present work, the anti-oxidative effect of RTE on oils and fats in autoxidation or thermal oxidation was studied, and it was confirmed that RTE has a very strong anti-oxidative effect on emulsifying oils owing to the water-soluble polyphenols such as rutin and quercetin contained in RTE. RTE was found to have a strong ability to quench radicals generated in the water phase, and to confer higher thermal stability against deep fat frying than tocopherol. But RTE showed little anti-oxidative effect on frying oil because of its lower oil-solubility.

Evaluation of the hepatotoxic and hepatoprotective effect of Rwandese herbal drugs on in vivo (guinea pigs barbiturate-induced sleeping time) and in vitro (rat precision-cut liver slices, PCLS) models

Exp Toxicol Pathol. 2009 Jun 1; Mukazayire MJ, Allaeys V, Buc Calderon P, Stévigny C, Bigendako MJ, Duez PPrecision-cut liver slices (PCLS) preserve the tissular organization of the organ and represent an in vitro model closer to in vivo conditions than hepatocytes cultures. As this may be an interesting tool not only for the investigation of hepatotoxic and protective effects but also for bioguided fractionations schemes, the usefulness of PCLS was compared with an in vivo test of liver function. Crude extracts derived from five herbs used in Rwanda for hepatoprotective activity were tested on CCl(4)-treated guinea pigs by the method of barbiturate-induced sleep modification. Aqueous extracts of Ocimum lamiifolium, Crassocephalum vitellinum, Guizotia scabra and Vernonia lasiopus leaves allowed animals to recover barbiturate sleep duration in proportions of 88%, 78%, 61% and 34%, respectively and Microglossa pyrifolia was found inactive. Dried methanolic extracts of the 5 plants were then tested in vitro on rat PCLS for protection against acetaminophen-induced hepatotoxicity. In this model, G. scabra, M. pyrifolia and V. lasiopus were found hepatotoxic by themselves and unable to prevent acetaminophen toxicity. The most active extract, obtained from O. lamiifolium, was subjected to bioassay-guided fractionation by chromatography on Si-C(18) to yield two quite active fractions. From a single animal, at least 50 PCLS explants can be prepared, which allows testing large amounts of samples, strengthening ethnopharmacological data on hepatoprotective medicinal plants and investigating hepatotoxic effects.