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Fullerene-DBP conjugates: Their co-occurrence in meteorites, ammonites and Shilajit, and application in systemic drug delivery
Abstract
A unified manifestation of the macrocosmic and microcosmic actions is expressed by the co-occurrence of C60-fullerene-dibenzo-α- pyrone (DBP) conjugates in meteorites, ammonites, and Shilajit. The crystal forms of mineral (aragonite) deposition in ammonites (the major marine precursors of Shilajit), are distinctly different in many respects from the inorganic mineral, aragonite. The mineral deposition in the living ammonite shells is under strict biological control and involves organo-mineral complexes received from meteorites. These constituents in ammonites are eventually transformed into Shilajit by humification. Hence, the supramolecular assemblies of complex chemical constituents of ammonites, in many respects, show striking similarities with the humic constituents (FAs, HAs and HMs) of meteorites and of Shilajit. Some selected assemblies, viz. fusoms and DCPs, of Shilajit, comprising of fullerene-DBP conjugates in their inner core, were found to confer facile water-solubility, stability and superior bioavailability (Yogabahi in Ayurveda) to a host of chemical agents that are ordinarily water-insoluble, thermolabile, autoxidizable, and/or prematurely biodegradable before reaching the target site. The potential of this superior drug delivery system is evaluated.
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The Tagish Lake meteorite fell last year on a frozen lake in Canada and may provide the most pristine material of its kind. Analyses have now shown this carbonaceous chondrite to contain a suite of soluble organic compounds (approximately 100 parts per million) that includes mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic hydrocarbons. The insoluble carbon exhibits exclusive aromatic character, deuterium enrichment, and fullerenes containing "planetary" helium and argon. The findings provide insight into an outcome of early solar chemical evolution that differs from any seen so far in meteorites.
The carbonaceous chondrite meteorites are fragments of asteroids that have remained relatively unprocessed since the formation of the solar system 4.6 billion years ago. These carbon-rich objects contain a variety of extraterrestrial organic molecules that constitute a record of chemical evolution prior to the origin of life. Compound classes include aliphatic hydrocarbons, aromatic hydrocarbons, amino acids, carboxylic acids, sulfonic acids, phosphonic acids, alcohols, aldehydes, ketones, sugars, amines, amides, nitrogen heterocycles, sulfur heterocycles and a relatively abundant high molecular weight macromolecular material. Structural and stable isotopic characteristics suggest that a number of environments may have contributed to the organic inventory, including interstellar space, the solar nebula and the asteroidal meteorite parent body. This review covers work published between 1950 and the present day and cites 193 references.
A fundamental problem of tracing the sequence of primordial organic chemistry is the identification of the primitive organic molecules, from among the currently known millions of possible compounds. The observed intimate association, for ages, of a selected group of organic compounds, e.g. hydroxyacetophenones and oxygenated dibenzo-α-pyrones (DBPs), and of the Ayurvedic maharasas (inorganic minerals), in their natural habitats, is regarded as a strong circumstantial evidence in support of an organized sequence of primordial organic chemistry. These phenolic compounds also occur, selectively and consistently within the core of 'till' and boulders of the Gangotriglacier (1 to 60 million-year-old). Another unique feature of these compounds is that the DBPs are found in the organ deposits of several insects (haemolymph gland), animals (scent-gland, clover-stone), and in man (kidney and gall stone), but rarely so in plants. This phenomenon suggests their non-photosynthetic (abiotic) origin, at least partly, which is also supported from their high δ13C values. These organic compounds seem to bear a link between the primordial and the modern eras of organic chemistry on earth.
Liposome entrapped adriamycin retains its full cytotoxic potential when tested under conditions against murine leukemia L-1210 cells. drug distribution studies indicate that, relative to the free drug, a lower proportion of adriamycin administered in the liposome form is delivered to the heart and kidneys at one and four hours after injection. When administered to normal mice in high doses, anionic adriamycin liposomes appear less harmful than equal doses of the free drug as judged by alterations in animal weight gain. In these studies, a noval double packing procedure has been used for the entrapment of adriamycin in phospholipid vesicles.
In recent years, there has been an increased understanding of P-glycoprotein (P-GP)-mediated pharmacokinetic interactions. In addition, its role in modifying the bioavailability of orally administered drugs via induction or inhibition has been also been demonstrated in various studies. This overview presents a background on some of the commonly documented mechanisms of multidrug resistance (MDR), reversal using modulators of MDR, followed by a discussion on the functional aspects of P-GP in the context of the pharmacokinetic interactions when multiple agents are coadministered. While adverse pharmacokinetic interactions have been documented with first and second generation MDR modulators, certain newer agents of the third generation class of compounds have been less susceptible in eliciting pharmacokinetic interactions. Although the review focuses on P-GP and the pharmacology of MDR reversal using MDR modulators, relevance of these drug transport proteins in the context of pharmacokinetic implications (drug absorption, distribution, clearance, and interactions) will also be discussed.
SINCE carbon nanotubes1 were first synthesized
in macroscopic quantities2, it has become possible to explore
their physical and chemical characteristics. There has been much
speculation3 about the properties of materials encapsulated
within the tubes, but experimental studies of this issue require a reliable
means of open-ing and filling the tubes. Various approaches have been developed
for opening up46 the tube ends and encapsulating
material4,6,7, but these work only for a limited range of
materials or in low yield. Here we describe a general method that allows carbon
nanotubes to be opened at the end and filled with a variety of metal oxides
using wet chemical techniques. We anticipate that this method will lead to
extensive study of the chemistry and physics of filled nanotubes, which might
find applications in catalysis, separation and storage technology and in the
development of materials with new magnetic and electrical properties.
INFRARED emission features consisting of narrow lines and broad plateaux, ranging from 3 μm in wavelength to over 12 μm, are seen in a wide variety of astronomical objects in which interstellar or circumstellar gas is illuminated by ultraviolet radiation from a star. Several candidates have been proposed as the source of this emission, but none is widely accepted. Here I calculate the vibrational spectrum of the fullerane C60H60, the saturated hydride of the soccerball-shaped molecule C60, using a force-field model. Six of the infrared active frequencies match unidentified emission lines to within 4%, and a seventh differs from an observed line by 8%. The calculation suggests why the astronomical feature at 7.7 μm is the strongest, and the observed variation of the 3.4 μm and 3.28 μm features with astrophysical environment is consistent with the idea that the former is attributable to stretching of the C–H bond in heavily hydrogenated fulleranes, whereas the latter is due to the same transition in lightly hydrogenated fulleranes.
The preparation of a 3:1 complex of hydroquinone (HQ) and C60, (HQ)3C60, is reported and its X-ray crystal structure described. The HQ host builds up a single H-bonded super-polonium network with super-cubes as building blocks, which accommodate the large C60 guest molecules. The enclathration of C60 is rather tight (high density of the complex) owing, in part, to favorable charge-transfer host-guest interactions (π-donor-acceptor complex). Nonetheless, the C60 molecules arc orientationally disordered, and no individual bond lengths could be measured. In contrast, the HQ host network is essentially ordered and well-defined with normal intramolecular geometry. No appreciable (powder) conductivity could be observed for (HQ)3C60, yet ESR spectra of single crystals showed interesting narrow signals.
Mangiferin, a naturally occurring glucosylxanthone, was assessed for its immunomodulatory potential. The phytochemical induced extensive in vitro proliferation of murine splenocytes and thymocytes at the doses of 5-40 micrograms ml-1. Suppression of the proliferative response of the cells was observed with higher doses of mangiferin. Mangiferin also activated the splenocytes of tumor hosts at early and late stages of tumor growth. The Phytohemagglutinin (PHA) and Con A unresponsive splenocytes of advanced tumor bearer proliferated extensively in response to mangiferin. Mangiferin when used with Con A produced additive stimulatory effect and induced heightened DNA synthesis of normal and advanced tumor bearers' splenocytes.
The isolation and preparation ten years ago of the fullerenes in bulk quantities, sparked off a truly remarkable interdisciplinary research activity, encompassing diverse fields of chemistry, physics, materials science and medicinal chemistry. Pharmaceutical and biological studies have revealed that fullerene-based compounds exhibit various types of biological activity either in vitro or in vivo and are discussed in this review.