Hibiscus sabdariffa LINN. (roselle) is widely cultivated in tropical areas and its red persistent calyx is the major component possessing a sour taste that is used as beverage and food colorants. It contains many chemical constituents including alkaloids, L-ascorbic acid, anisaldehyde, anthocyanin, bcarotene, b-sitosterol, citric acid, cyanidin-3-rutinoside, delphinidin, galactose, gossypetin, hibiscetin, mucopolysaccharide, pectin, protocatechuic acid, polysaccharide, quercetin, stearic acid and wax. As a traditional medicine, it is claimed to be effective against kidney stones and urinary bladder stones.1,2) It is also used for its antibacterial, antifungal, hypocholesterolemic, antispasmodic and antihypertensive actions. [3][4][5][6] Numerous studies have linked the elevation of plasma low-density lipoprotein (LDL)-cholesterol (LDL-C) level with the increased incidence of atherosclerotic events. LDL particles undergo extensive lipid peroxidation, resulting in generation of oxidized LDL and formation of atherosclerotic lesions. [7][8][9][10][11] Predictably, antioxidants such as a-tocopherol and probucol have been found to reduce LDL oxidation. [12][13][14][15] Various antioxidant constituents have been found in the calyx of Hibiscus sabdariffa LINN., including hibiscus anthocyanin, quercetin, L-ascorbic acid and protocatechuic acid (PCA). Antioxidant effects of roselle extracts have been investigated in many experimental models, [16][17][18][19] however the antioxidant effects of Hibiscus sabdariffa LINN. on LDL oxidation have so far not been fully determined. The present study was designed to quantitatively investigate the antioxidant effect of roselle on the oxidative modification of LDL induced by CuSO 4 in vitro by monitoring the formation of conjugated dienes and the formation of thiobarbituric acid reactive substances (TBARs). MATERIALS AND MATHODS Plant Material and ExtractsThe dried calyxes of roselle were blended to a fine powder and one kilogram of powders was extracted with 1 l of water and filtered through filter paper by suction. The filtrates were pooled and dried at 50°C in a rotary evaporator. The average yield of the extract was 45.0%. The extracts were stored in a dark, moisture-free container at 4°C. The antioxidant effect of PCA, a polyphenolic compound, has been investigated and found to exhibit potent action in primary cultures of rat hepatocytes induced by tert-butylhydroperoxide (t-BHP).18) Therefore, in the present experiment, PCA content in the calyx of roselle was used for the standardization of batches; 25 mg of dried calyx extracts contained 10.98 mg of PCA. For this experiment, 150 mg of the crude extracts were dissolved in 1 ml of distilled water.Reagents Disodium ethylene diamine was purchased from Mallinckrodt Inc. (St. Louis, MO, U.S.A.) and sodium chloride, sodium carbonate and sodium hydroxide from Merck (Haar, Germany). Diethylether was purchased from BDH laboratory supplies (Poole, England). Thiobarbituric acid, potassium bromide, disodium phosphate, sodium phosphate, sod...

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Doxorubicin is an important and effective anticancer drug widely used for the treatment of various types of cancer but its clinical use is limited by dose-dependent cardiotoxicity. Elevated tissue levels of cellular superoxide anion/ oxidative stress are a mechanism by which doxorubicin-induced cardiotoxicity. Selected medicinal plant extracts were tested for their antioxidant capacity and cardioprotective effect against doxorubicin-induced cardiotoxicity. The cardiac myoblasts H9c2 were incubated with the antioxidants ascorbic acid, trolox, N-acetylcysteine or selected medicinal plant extracts including; 1) ethanolic extracts from Curcuma longa L-EtOH Phyllanthus emblica L-EtOH, and Piper rostratum Roxb-EtOH; and 2) water extracts from Curcuma longa L-H 2 O and Morus alba L-H 2 O. The cardioprotective effects of these extracts were evaluated by crystal violet cytotoxicity assay. IC50s of doxorubicin were compared in the presence or absence of ascorbic acids, trolox, N-acetylcysteine or plant extracts. Morus alba L-H 2 O showed the highest antioxidant properties evaluated by ferric reducing/antioxidant power assay. Ascorbic acid and N-acetylcysteine had modest effects on the protection of doxorubicin-induced cytotoxicity while trolox showed insignificant protective effect. All plant extracts protected cardiac toxicity at different degrees except that Curcuma longa L-EtOH had no protective effect. Phyllanthus emblica-EtOH (100 mg/ml) showed the highest cardioprotective effect (∂12-fold doxorubicin IC50 increase). The data demonstrate that antioxidants from natural sources may be useful in the protection of cardiotoxicity in patients who receive doxorubicin.Doxorubicin is an effective and broadspectrum antineoplastic agent used in the treatment of a variety of haematologic and solid malignacies, such as leukaemias, bladder, lung, and breast cancers, Hodgkin's and non-Hodgkins lymphomas, and ovarian cancer. Its clinical uses are often limited by the adverse effect cardiotoxicity. An initial acute effect includes hypotension and transient electrocardiographic abnormalities reported up to 41% of patients. The chronic effects may occur several weeks or months after cumulative doxorubicin administration, and the occurrence is dose-dependent cardiomyopathy which accounts for as high as 50% mortality within 2 years after diagnosis (Felker et al. 2000;Jensen et al. 2002). Recent studies demonstrate that increased reactive oxygen species generation, especially superoxide and hydrogen peroxide, is implicated in the mechanisms of doxorubicin-induced cardiotoxicity (Kalivendi et al. 2001;Wang et al. 2004). The high level of doxorubicin could damage membranes, proteins (e.g., enzymes, structural, and receptors), and DNA that may lead to cardiac dysfunction and apoptosis (Arola et al. 2000;Yamaoka et al. 2000;Green & Leeuwenburgh 2002;Kumar et al. 2002). While the cytoprotective effect of the commonly used antioxidant vitamins (ascorbic acid and vitamin E) remains controversial (Legha et al. 1982;Shimpo et al. 1991b;Q...

Three new dammarane triterpenes, bruguierins A-C (1-3), were isolated from a petroleum ether extract of the flowers of Bruguiera gymnorrhiza. Their structures were determined on the basis of physical and spectroscopic data interpretation. With stably transfected HepG2 cells, the three isolates activated antioxidant response element (ARE luciferase activation) with EC(50) values of 7.8, 9.4, and 15.7 microM, respectively. Bruguierin A (1) also inhibited phorbol ester-induced NFkappaB (nuclear factor-kappaB) luciferase activation with an IC(50) value of 1.4 microM and selectively inhibited cyclooxygenase-2 (COX-2) activity with an IC(50) value of 0.37 microM. Compounds 2 and 3 were not active in these bioassays.