Chemical Constituents of Rhododendron lepidotum
Two new coumarin glycosides, 7-O-β-D-glucopyranosyl-8-methoxybenzopyranone (1) and 7-hydroxy-8-O-β-glycosylbenzopyranone ((2), are reported along with the isolation of 7,8-dihydroxy coumarin (daphnetin) from Rhododendron lepidotum (aerial part).
Chemical Constituents of Rhododendron lepidotum from Nepal Himalayas
Rhododendron lepidotum (family Ericaceae) is a highly variable, low and compact to upright, lean shrub, up to 2 m tall. The flowers are of open type, having a white, yellow, pink, or purple color. The leaves are elliptic with a dark green upper surface and a lower surface with large brownish scales. The distribution of R. lepidotum is from Kashmir to southeastern Tibet at an altitude ranging from 2400 to 4900 m. The genus Rhododendron has a long history of use as folk medicine in various countries. Rhododendron adamsii Rehder is used as a stimulant and tonic [1, 2]. Dried leaves of R. dauricum are used as an expectorant and in the treatment of acute and chronic bronchitis [3, 4]. The leaves and twigs of R. dauricum display significant anti-HIV activity [5]. The leaf and flower powder of R. lepidotum have been used as a snuff in the treatment of headache [6], etc. Coumarin glycosides such as rhodonin and rhodonetin [7], 7-O--D-glucopyranosyl-8-methoxybenzopyranone and 7-hydroxy-8-O--glycosylbenzopyranone [8], coumarins named daphnin, daphnetin, daphnetin glucoside, rhodonetin, rhodonin, and umbelliferone [9], 2,4,6-trihydroxacetophenone3,5-di-C--D-glucoside, lupeol, ursolic acid, avicularin, quercetin, myricetin, hyperoside, myricetin-3-O--Dxyloside, (+)-taxifolin-3-O--L-arabinopyranoside, (+)-taxifolin-3-O--D-glucopyranoside, lyoniside, confluentin, 2-(4-hydroxyphenyl)-ethyltriacontanoate, 2,6-dimethoxy-4-hydroxyphenyl-1-O--D-glucopyranoside, (–)-2-hydroxy-5-(2-hydroxyethyl)phenyl-O--D glucopyranoside, (–)-isolariciresinol, and isofraxoside [10] have been isolated from R. lepidotum. The leaves and twigs of Rhododendron lepidotum were collected from Godha Tabala Village of Langtang National Park (3800 m) of Nepal during November 2008. Four new compounds have been characterized from its biologically active crude methanol extract. Previously, the activity of the crude extract was determined by antimicrobial, IC50, brine shrimp, and antiproliferative (HeLa cell) tests [11]. The water-insoluble portion of the methanol extract was subjected to column chromatography to afford four triterpenoids (1–4). Compound 1 was obtained as a white solid on crystallization from acetone. The IR spectrum showed an ester carbonyl, and three methyl protons appeared in the 1H NMR spectrum, which was further supported by a peak at m/z 408 (M – CH3CO2H) in addition to the [M]+ 468 corresponding to the molecular formula C32H52O2 for 1. The 1H NMR spectrum showed the presence of a terminal alkene besides a vinylic methyl. The 13C NMR and DEPT confirmed CHEMICAL CONSTITUENTS OF Rhododendron lepidotum FROM NEPAL HIMALAYAS
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.