This review describes our recent studies on the carbon-carbon bond forming reactions of a-chlorosulfides with arenes, alkenes, and alkynes. Applications of these reactions to the synthesis of natural products are also presented.
The progress of the asymmetric syntheses of nitrogen-containing biologically active compounds such as pyrrolidine, pyrrolizidine, indolizidine alkaloids, and unusual amino acids has been reviewed. Our recent advances in taking advantage of stereoselective aminocyclization of homochiral N-alkenyl urethanes and thioimidates containing allylic hydroxyl group have provided an attractive entry into the functionalized pyrrolidine skeletones as chiral building blocks. A promising approach to a number of biologically active compounds such as alkaloids has emerged.
The methanol extract from the bark of Myrica rubra SIEB. et ZUCC. showed protective effects on liver injuries induced by carbon tetrachloride(CCl4) and α-naphthylisothiocyanate (ANIT) in rats. In this study, the fractions and some compounds from the bark of M. rubra were investigated for the protection against CCl4 inducing liver injuries in rats. The active principles for the protection were recognized in two fractions(M-3 and M-5 Fr. 1) obtained from the methanol extract, and one of the active principles in the fraction (M-3) was found to be myricanol 5-O-β-D-(6'-O-galloyl)-glucopyranoside. In addition, these fractions protecting liver injuries induced by CCl4 showed significant protective effects against cholestasis induced by ANIT.
The distribution and the anti-lipidperoxidative effects of porphyrins in the hepatic subcellular fractions in rats were studied after intravenous administration of protoporphyrin (PP). PP and/or PP-derived porphyrins were mainly distributed in the membrane-containing fractions of 600×g-, 10000×g- and 100000×g-sediment from the liver homogenates of rats receiving a 20 mg/kg dose of PP. The lipid peroxidation induced by L-ascorbic acid in the fractions of 600×g-, 10000×g-and 100000×g-sediment from the PP-treated rats was suppressed during 1-168 h, 1-168 h and 12-168 h, respectively, after the PP treatment. The suppression of the peroxidation in the liver mitochondria from the PP- treated rats was further enhanced by the addition of the hepatic cytosol from the PP-treated rats. The extent of the suppression by the addition of the cytosol from the PP-treated rats at 24 h after the PP administration was greater than those at 0 and 168 h after the PP administration. These results indicate that PP and/or PP-derived porphyrins distributed in the liver still exert antioxidative actions and that there might exist some unknown factors enhancing the actions in the hepatic cytosol.
Of twelve reduced and acetylated derivatives of shikonin, a chemical constituent of Shikon, the accelerating activity on granuloma formation and the inhibitory activity on delayed-type allergy were investigated in order to find a compound having more characteristic effect than shikonin on wound healing in experimental animals. As a result, it was found that a reduced and pentaacetylated derivative of shikonin, MDS-004, has more excellent pharmacological activity. MDS-004 (0.1-1 mg/pellet) accelerated dose-dependently felt-pellet-induced granuloma formation when given topically together with felt-pellets in rats. It also produced strong inhibition against delayed-type allergies (ear edema) caused by oxazolone and dinitrofluorobenzene by topical application of up to 1 mg/ear to the ear skin of mice; its potency was far superior to that of shikonin. Orally administered MDS-004, unlike shikonin, inhibited carrageenan-induced hind paw edema, and exhibited tendency to heal acetic acid-induced gastric ulcer in rats. However, MDS-004, as well as commercial wound healing drugs tested and shikonin, did not show any healing action in the incised and open wound models in rats, if applied topically to the wound as 5 and 10% powders. On the other hand, MDS-004 did not produce irritative action on the ear skin at a topical dose of 1 mg/ear different from shikonin, and any behavioral changes after oral administration of 100 mg/kg in mice. These results suggest that a white powder MDS-004, different from deep purple shikonin, has accelerating action on glanuloma formation without irritative action and stronger inhibitory action on delayed-type allergy by topical application than shikonin.
A simple method using ion-pair high-rerformance liquid chromatography was established for the rapid and precise determination of sennoside A in oriental pharmaceutical decoctions containing Rhei Rhizoma. This method was compared with other two methods, i.e. ion-suppression and phosphate buffer methods. Sennoside A was eluted without interference in this ion-pair method, while the determination of sennoside A was interfered by co-existing components in the other two methods.
Effects of 50% methanolic extract (U-ext) from the leaf of Arctostaphylos uva-ursi (L.) SPRENG, (bearberry leaf) on melanin synthesis were investigated in vitro. The U-ext and arbutin isolated from the bearberry leaf had an inhibitory effect on tyrosinase activity. Furthermore, the U-ext inhibited the production of melanin from dopa by tyrosinase and from dopachrome by autoxidation. These results suggest that the bearberry leaf was found to be an effective inhibitor of the production of melanin.