Ultrasound-Assisted Extraction of Polyphenols from Ginger (Zingiber officinale) and Evaluation of its Antioxidant and Antimicrobial Properties

In this present study, ultrasound-assisted solvent extraction conditions were optimized to develop a more efficient method that would result in maximum extraction of polyphenols from ginger. To achieve this optimal extraction process, a central composite design of response surface methodology was applied. A second-order polynomial equation was developed, indicating the effect of ginger concentration (400-1,200 mg/20mL solvent), solvent mixture composition (20-100%), temperature (30-70°C) and treatment time (10-30 min) on polyphenols extraction. The optimum parameters were found to be 1200mg of ginger prepared with 86% ethanol and sonication for 11 minutes at 65°C. The total phenolic and flavonoid content of ginger was found to be 1039.64 mg Gallic acid equivalent (GAE)/g and 492.57±3.5 mg Quercetin equivalent (QE)/g of ginger extract (dry weight), respectively. The ginger extract proved to have significant antioxidant capacity with a DPPH radical scavenging activity of 54.5% noted and further proved to have strong antimicrobial effects against Escherichia coli, Salmonella typhimurium, Bacillus cereus and Staphylococcus aureus with diameter of inhibition zone (DIZ) values of 14.49mm, 15.10mm, 16.74mm and 13.88mm recorded respectively, MIC values ranging from 3.75 – 7.5mg/ml and an extract concentration of 7.5mg/ml required to exert bactericidal effects against B.cereus and 15mg/ml for all other strains. All values obtained were comparable to that of synthetic preservatives sodium nitrite and sodium benzoate thus demonstrating the superior potential of this spice for future application as a natural food preservative

Relativistic Dynamics and Extreme Mass Ratio Inspirals

It is now well-established that a dark, compact object (DCO), very likely a massive black hole (MBH) of around four million solar masses is lurking at the centre of the Milky Way. While a consensus is emerging about the origin and growth of supermassive black holes (with masses larger than a billion solar masses), MBHs with smaller masses, such as the one in our galactic centre, remain understudied and enigmatic. The key to understanding these holes - how some of them grow by orders of magnitude in mass - lies in understanding the dynamics of the stars in the galactic neighbourhood. Stars interact with the central MBH primarily through their gradual inspiral due to the emission of gravitational radiation. Also stars produce gases which will subsequently be accreted by the MBH through collisions and disruptions brought about by the strong central tidal field. Such processes can contribute significantly to the mass of the MBH and progress in understanding them requires theoretical work in preparation for future gravitational radiation millihertz missions and X-ray observatories. In particular, a unique probe of these regions is the gravitational radiation that is emitted by some compact stars very close to the black holes and which could be surveyed by a millihertz gravitational wave interferometer scrutinizing the range of masses fundamental to understanding the origin and growth of supermassive black holes. By extracting the information carried by the gravitational radiation, we can determine the mass and spin of the central MBH with unprecedented precision and we can determine how the holes "eat" stars that happen to be near them.Comment: Update from the first version, 151 pages, accepted for publication @ Living Reviews in Relativit

Mutagenesis of the Yeast Reductase Gene, YDL124w

This presentation was given at the Biocatalysis Gordon Conference

Characterizing the Substrate Binding Specificity of an Aldo-Keto Reductase YDL124w

This presentation was given at the ACS National Meeting