Effects of zinc supplementation on the plasma glucose level and insulin activity in genetically obese (ob/ob) mice.

The effects of zinc supplementation (20 mM ZnCl2 from the drinking water for eight weeks) on plasma glucose and insulin levels, as well as its in vitro effect on lipogenesis and lipolysis in adipocytes were studied in genetically obese (ob/ob) mice and their lean controls (+/?). Zinc supplementation reduced the fasting plasma glucose levels in both obese and lean mice by 21 and 25%, respectively (p < 0.05). Fasting plasma insulin levels were significantly decreased by 42% in obese mice after zinc treatment. In obese mice, zinc supplementation also attenuated the glycemic response by 34% after the glucose load. The insulin-like effect of zinc on lipogenesis in adipocytes was significantly increased by 80% in lean mice. However, the increment of 74% on lipogenesis in obese mice was observed only when the zinc plus insulin treatment was given. This study reveals that zinc supplementation alleviated the hyperglycemia of ob/ob mice, which may be related to its effect on the enhancement of insulin activity.

Synthesis and antithrombotic effect of xanthone derivatives.

A series of xanthone derivatives was synthesized and tested in-vitro for their ability to inhibit aggregation of rabbit washed platelets and human platelet-rich plasma (PRP) induced by various inducers. 2-Prenyloxyxanthone showed the most potent inhibition of rabbit washed platelet aggregation induced by arachidonic acid (1C50 = 10.2 microM). Of the compounds tested in human PRP, 2-[3 (propylamino)-2-hydroxypropoxy]xanthone (4) hydrochloride salt exhibited the most potent inhibition of platelet aggregation induced by adrenaline (IC50 = 4.4 microM), whereas in evaluation of mouse antithrombotic activity, compound 4 exhibited the most potent protection of mice from thrombotic challenge. Compound 4, 2-[3-(isopropylamino)-2-hydroxypropoxylxanthone hydrochloride salt and 2,5 dihydroxyxanthone suppressed the secondary aggregation induced by adrenaline in human PRP. We conclude that the antiplatelet effects of these compounds are mainly due to an inhibitory effect on thromboxane formation.

Synthesis and anti-inflammatory effects of xanthone derivatives.

Eighteen synthetic xanthone derivatives were tested for their inhibitory effects on the activation of mast cells and neutrophils. 1,3- and 3,5-Dihydroxyxanthone showed strong inhibitory effects on the release of beta-glucuronidase and histamine from rat peritoneal mast cells stimulated with compound 48/80. 1,6-Dihydroxyxanthone and 1,3,8-trihydroxyxanthone showed strong inhibitory effects on the release of beta-glucuronidase, and beta-glucuronidase and lysozyme, respectively, from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP). 1,3- and 1,6-Dihydroxyxanthone, 1,3,7-trihydroxyxanthone, and 1,3,5,6-, 2,3,6,7-, and 3,4,5,6-tetrahydroxyxanthone showed potent inhibitory effects on superoxide formation of rat neutrophils stimulated with fMLP. 1,6- and 3,5-Dihydroxyxanthone showed remarkable inhibitory effects on hind-paw oedema induced by polymyxin B in normal as well as in adrenalectomized mice. These data indicated that the anti-inflammatory effect of these compounds is mediated through the suppression of chemical mediators released from mast cell and neutrophil degranulation.

Xanthone derivatives as potential anti-cancer drugs.

Xanthone derivatives have been shown to be potent inhibitors of tumour growth. Oxygenated xanthones and [3-(dialkylamino)-2-hydroxypropoxy]xanthones have been prepared and tested for in-vitro inhibition of human PLC/PRF/5, KB and 212 cells. Structure-activity analysis indicated epoxidation of the hydroxyxanthone increased cytotoxicity against tumour cells but ring-opening of the epoxide group with dialkylamine did not enhance the anti-tumour activity. Further evaluation of three of the most active compounds 2, 6-, 3, 6-, and 3, 5-di(2,3-epoxypropoxy)xanthone (compounds 10a, 11a, and 12a, respectively) in DNA, RNA and protein synthesis of tumour cells showed potent inhibitory activity. The 3,5-di(2,3-epoxypropoxy)xanthone also showed potent inhibitory activity against 212 cells, a Ha-ras oncogene-transformed NIH 3T3 cell line. The results indicated that compounds 10a and 12a are potent anti-tumour agents which not only suppressed cellular DNA, RNA and protein synthesis but also specifically inhibited the Ha-ras oncogene in 212 cells.

Guaiacoxypropanolamine derivatives of capsaicin: a new family of beta-adrenoceptor blockers with intrinsic cardiotonic properties.

A series of guaiacoxypropanolamine derivatives of capsaicin was synthesized by replacing the phenolic OH of N-nonanoylvanillamide with epichlorohydrin, followed by cleavaging the obtained epoxide compound with alkylamines. Intravenous injection of these propanolamine derivatives (1 mg/kg) in normotensive Wistar rats induced a transient fall in blood pressure but significantly reduced the heart rate for more than 30 min. These derivatives (10(-8)-10(-6) M) inhibited isoproterenol (10(-10)-10(-5) M)-induced positive chronotropic and inotropic effects in isolated guinea pig atrium. On the other hand, these derivatives (10(-5)-10(-4) M) exhibited a positive cardiotonic effect that is independent of intrinsic sympathomimetic effects. Investigation of the structure-activity relationship of these derivatives revealed that the position of the oxypropanolamine side chain and substituents of the 4-OH position play significant roles in imparting their pharmacological effects. Of the derivatives tested, the most effective one was compound 9. In conclusion, the results obtained from in vitro and in vivo studies suggested that these derivatives and compound 9 may be expected to be beta-adreneoceptor blocking agents with nonadrenergic positive chronotropic and inotropic properties.

Xanthonolol: a calcium channel and beta-adrenoceptor blocker with vasodilating properties.

1. Xanthonolol (0.1-5.0 mg/kg, i.v.) reduced the blood pressure, heart rate, and L-isoproterenol (0.05 microgram/kg, i.v.)-induced tachycardia in rats. 2. In the isolated guinea-pig right atrium, xanthonolol (10(-6)-3 x 10(-4) M) produced long-lasting negative, inhibited L-isoproterenol-induced positive chronotropic effects, prevented the rate-increasing effects of increased extracellular Ca2+ (3.0-9.0 mM), and inhibited Ca2+ (3.0-9.0 mM)-induced heart rate-increase. 3. In the isolated guinea-pig thoracic aorta, the contractions induced by CaCl2 (0.1-5.0 mM) were inhibited by xanthonolol (10(-6)-10(-4) M). 4. Xanthonolol is suggested to have a calcium channel and beta adrenergic blocking effect with vasodilating properties.