STATISTICAL OPTIMIZATION AND STABILITY STUDY OF QUERCETIN-LOADED MICROEMULSION

Objective: This research aims to develop a quercetin microemulsion system to improve the solubility of quercetin and to study the stability of the microemulsions. Methods: The microemulsion is prepared by water titration method using isopropyl myristate (oil), Tween 60®/Span 80® (3:2) (surfactant) and ethanol (co-surfactant). Two different aqueous phases, water or NaCl solution, were used to prepare microemulsions and the influence of each parameter was described. DPPH scavenging and anti-tyrosinase activity were performed along with chemical stability to evaluate the functional stability of microemulsions. Results: The influence of percentage of oil phase (variable A) on the solubility of quercetin was less significant than that of percentage of surfactant/co-surfactant (variable B). Compared to those prepared with water (variable C), the solubility of quercetin in microemulsions prepared with NaCl solution significantly increased. The ratio of the high level to low level for solubility of three variables was 1.135, 1.315 and 1.591 respectively. Increasing variable A and B led to an increase in the particle size of microemulsions from 120.08 nm to 188.38 nm and 48.18 nm to 260.28 nm, respectively. The influence of variable B was quite significant, while variable C has no significant effect on particle size. Quercetin microemulsions showed good chemical and functional stability when stored at 4 °C. Under other conditions, especially at 40 °C, the activity of the microemulsion is considerably reduced. Conclusion: The influence of different variables on the characteristics of microemulsions was complicated. Care must be taken in the composition and storage conditions of these formulations

Conservation genetics and phylogeography of endangered and endemic shrub Tetraena mongolica (Zygophyllaceae) in Inner Mongolia, China

<p>Abstract</p> <p>Background</p> <p><it>Tetraena mongolica </it>(Zygophyllaceae), an endangered endemic species in western Inner Mongolia, China. For endemic species with a limited geographical range and declining populations, historical patterns of demography and hierarchical genetic structure are important for determining population structure, and also provide information for developing effective and sustainable management plans. In this study, we assess genetic variation, population structure, and phylogeography of <it>T. mongolica </it>from eight populations. Furthermore, we evaluate the conservation and management units to provide the information for conservation.</p> <p>Results</p> <p>Sequence variation and spatial apportionment of the <it>atp</it>B-<it>rbc</it>L noncoding spacer region of the chloroplast DNA were used to reconstruct the phylogeography of <it>T. mongolica</it>. A total of 880 bp was sequenced from eight extant populations throughout the whole range of its distribution. At the cpDNA locus, high levels of genetic differentiation among populations and low levels of genetic variation within populations were detected, indicating that most seed dispersal was restricted within populations.</p> <p>Conclusions</p> <p>Demographic fluctuations, which led to random losses of genetic polymorphisms from populations, due to frequent flooding of the Yellow River and human disturbance were indicated by the analysis of BEAST skyline plot. Nested clade analysis revealed that restricted gene flow with isolation by distance plus occasional long distance dispersal is the main evolutionary factor affecting the phylogeography and population structure of <it>T</it>. <it>mongolica</it>. For setting a conservation management plan, each population of <it>T</it>. <it>mongolica </it>should be recognized as a conservation unit.</p

An Astigmatic Detection System for Polymeric Cantilever-based Sensors

We demonstrate the use of an astigmatic detection system (ADS) for resonance frequency identification of polymer microcantilever sensors. The ADS technology is based on a DVD optical head combined with an optical microscope (OM). The optical head has a signal bandwidth of 80 MHz, allowing thermal fluctuation measurements on cantilever beams with a subnanometer resolution. Furthermore, an external excitation can intensify the resonance amplitude, enhancing the signal- to-noise ratio. The full width at half maximum (FWHM) of the laser spot is 568 nm, which facilitates read-out on potentially submicrometer-sized cantilevers. The resonant frequency of SU-8 microcantilevers is measured by both thermal fluctuation and excited vibration measurement modes of the ADS

Genetic population structure of the alpine species Rhododendron pseudochrysanthum sensu lato (Ericaceae) inferred from chloroplast and nuclear DNA

<p>Abstract</p> <p>Background</p> <p>A complex of incipient species with different degrees of morphological or ecological differentiation provides an ideal model for studying species divergence. We examined the phylogeography and the evolutionary history of the <it>Rhododendron pseudochrysanthum </it>s. l.</p> <p>Results</p> <p>Systematic inconsistency was detected between gene genealogies of the cpDNA and nrDNA. Rooted at <it>R. hyperythrum </it>and <it>R. formosana</it>, both trees lacked reciprocal monophyly for all members of the complex. For <it>R. pseudochrysanthum </it>s.l., the spatial distribution of the cpDNA had a noteworthy pattern showing high genetic differentiation (F_ST= 0.56-0.72) between populations in the Yushan Mountain Range and populations of the other mountain ranges.</p> <p>Conclusion</p> <p>Both incomplete lineage sorting and interspecific hybridization/introgression may have contributed to the lack of monophyly among <it>R. hyperythrum</it>, <it>R. formosana </it>and <it>R. pseudochrysanthum </it>s.l. Independent colonizations, plus low capabilities of seed dispersal in current environments, may have resulted in the genetic differentiation between populations of different mountain ranges. At the population level, the populations of Central, and Sheishan Mountains may have undergone postglacial demographic expansion, while populations of the Yushan Mountain Range are likely to have remained stable ever since the colonization. In contrast, the single population of the Alishan Mountain Range with a fixed cpDNA haplotype may have experienced bottleneck/founder's events.</p