Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

An on-line HPLC method for detection of radical scavenging compounds in complex mixtures

A rapid on-line method for screening of complex mixtures for radical scavenging components was developed using a methanolic solution of 2,2'-diphenyl-1-picrylhydrazyl (DPPH) stable free radical. The HPLC-separated analytes react postcolumn with the DPPH solution, and the induced bleaching is detected as a negative peak by an absorbance detector at 517 nm. An optimized instrumental setup is presented. The method is suitable for both isocratic and gradient HPLC runs with mobile-phase compositions ranging from 10 to 90␘rganic solvent in water or buffer (pH 3-6). The method is simple, has a broad applicability, and uses common instruments, inexpensive and stable reagents, and a time-saving and nonlaborious experimental protocol. It can also be used for quantitative analysis. The method was applied to several pure natural antioxidants and plant extracts. The limits of detection were 0.33-94 g/mL, depending on the compound tested

Polar constituents composition of endemic Sideritis italica (MILL.) GREUTER et BURTER from Central Italy

Endemic Sideritis italica (MILL.) GREUTER et BURTER (Lamiaceae) occurs mainly in Southern Italy and Sicily and has previously only been studied for the essential oil composition. In this paper, we complete the phytochemical study of a sample of S. italica, previously analysed for its volatile constituents, occurring in the Appennino Umbro-Marchigiano (Central Italy), which is the northern border of the areal distribution of the species. The analysis of medium polarity constituents led to the isolation of several glycosides, such as flavonoids, i.e. scutellarein derivatives; phenylethanoids, i.e. verbascoside; and iridoids, i.e. melittoside and 5-allosyloxy-aucubin, besides the diterpene siderol. The data reported have chemotaxonomic relevance, since they are in contrast with the hypothesis that in Lamiaceae the species producing iridoids do not usually have relevant essential oil production and vice versa

Chemical components and antioxidant activity of the volatile oil from Cassia tora L. seed prepared by supercritical fluid extraction

The seed of Cassia tora L. has been used as a traditional Chinese medicine for a long time and it is also an herbal tea in China. In this research, its volatile oil was recovered by employing supercritical fluid extraction using carbon dioxide and analyzed by gas chromatography (GC) and GC-mass spectrometry. The main components of the volatile oil were elucidated as (Z,Z)-9,12- octadecadienoic acid (26.74%), oleic acid (24.15%), n-hexadecanoic acid (13.99%), chrysophanol (7.26%), (E)-9-octadecenoic acid (4.52%) and octadecanoic acid (4.44%). This volatile oil was characterized by a high content of aliphatic acids (75.90%) and anthraquinones (7.26%). In the antioxidant assays, the volatile oil from C. tora L. seed demonstrated 2,2′-diphenyl-1- picryhydrazyl radical-scavenging activity in the concentration range from 20 to 500 g/mL, with the 50% inhibitory concentration (IC 50) value at 137 g/mL; it also showed a significant inhibitory effect against hydroxyl radicals with an IC 50 value of 67 g/mL, lower than that of quercetin (IC 50 = 8.15 g/mL), but superior to that of 4-terpineol (IC 50 = 87.5 g/mL). The observed antioxidant activity of this volatile oil is probably caused by the presence of high levels of chrysophanol and, possibly, (Z,Z)-9,12-octadecadienoic acid. © 2007, Blackwell Publishing.link_to_subscribed_fulltex